/* Functions to determine/estimate number of iterations of a loop.
- Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
+ Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
-Free Software Foundation; either version 2, or (at your option) any
+Free Software Foundation; either version 3, or (at your option) any
later version.
GCC is distributed in the hope that it will be useful, but WITHOUT
for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "basic-block.h"
#include "output.h"
#include "diagnostic.h"
+#include "intl.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "cfgloop.h"
#include "tree-data-ref.h"
#include "params.h"
#include "flags.h"
+#include "toplev.h"
#include "tree-inline.h"
+#include "gmp.h"
-#define SWAP(X, Y) do { void *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
+#define SWAP(X, Y) do { affine_iv *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
+/* The maximum number of dominator BBs we search for conditions
+ of loop header copies we use for simplifying a conditional
+ expression. */
+#define MAX_DOMINATORS_TO_WALK 8
/*
*/
-/* Returns true if ARG is either NULL_TREE or constant zero. Unlike
- integer_zerop, it does not care about overflow flags. */
+/* Bounds on some value, BELOW <= X <= UP. */
-bool
-zero_p (tree arg)
+typedef struct
{
- if (!arg)
- return true;
+ mpz_t below, up;
+} bounds;
- if (TREE_CODE (arg) != INTEGER_CST)
- return false;
- return (TREE_INT_CST_LOW (arg) == 0 && TREE_INT_CST_HIGH (arg) == 0);
+/* Splits expression EXPR to a variable part VAR and constant OFFSET. */
+
+static void
+split_to_var_and_offset (tree expr, tree *var, mpz_t offset)
+{
+ tree type = TREE_TYPE (expr);
+ tree op0, op1;
+ double_int off;
+ bool negate = false;
+
+ *var = expr;
+ mpz_set_ui (offset, 0);
+
+ switch (TREE_CODE (expr))
+ {
+ case MINUS_EXPR:
+ negate = true;
+ /* Fallthru. */
+
+ case PLUS_EXPR:
+ case POINTER_PLUS_EXPR:
+ op0 = TREE_OPERAND (expr, 0);
+ op1 = TREE_OPERAND (expr, 1);
+
+ if (TREE_CODE (op1) != INTEGER_CST)
+ break;
+
+ *var = op0;
+ /* Always sign extend the offset. */
+ off = double_int_sext (tree_to_double_int (op1),
+ TYPE_PRECISION (type));
+ mpz_set_double_int (offset, off, false);
+ break;
+
+ case INTEGER_CST:
+ *var = build_int_cst_type (type, 0);
+ off = tree_to_double_int (expr);
+ mpz_set_double_int (offset, off, TYPE_UNSIGNED (type));
+ break;
+
+ default:
+ break;
+ }
}
-/* Returns true if ARG a nonzero constant. Unlike integer_nonzerop, it does
- not care about overflow flags. */
+/* Stores estimate on the minimum/maximum value of the expression VAR + OFF
+ in TYPE to MIN and MAX. */
-static bool
-nonzero_p (tree arg)
+static void
+determine_value_range (tree type, tree var, mpz_t off,
+ mpz_t min, mpz_t max)
{
- if (!arg)
- return false;
+ /* If the expression is a constant, we know its value exactly. */
+ if (integer_zerop (var))
+ {
+ mpz_set (min, off);
+ mpz_set (max, off);
+ return;
+ }
- if (TREE_CODE (arg) != INTEGER_CST)
- return false;
+ /* If the computation may wrap, we know nothing about the value, except for
+ the range of the type. */
+ get_type_static_bounds (type, min, max);
+ if (!nowrap_type_p (type))
+ return;
+
+ /* Since the addition of OFF does not wrap, if OFF is positive, then we may
+ add it to MIN, otherwise to MAX. */
+ if (mpz_sgn (off) < 0)
+ mpz_add (max, max, off);
+ else
+ mpz_add (min, min, off);
+}
+
+/* Stores the bounds on the difference of the values of the expressions
+ (var + X) and (var + Y), computed in TYPE, to BNDS. */
+
+static void
+bound_difference_of_offsetted_base (tree type, mpz_t x, mpz_t y,
+ bounds *bnds)
+{
+ int rel = mpz_cmp (x, y);
+ bool may_wrap = !nowrap_type_p (type);
+ mpz_t m;
+
+ /* If X == Y, then the expressions are always equal.
+ If X > Y, there are the following possibilities:
+ a) neither of var + X and var + Y overflow or underflow, or both of
+ them do. Then their difference is X - Y.
+ b) var + X overflows, and var + Y does not. Then the values of the
+ expressions are var + X - M and var + Y, where M is the range of
+ the type, and their difference is X - Y - M.
+ c) var + Y underflows and var + X does not. Their difference again
+ is M - X + Y.
+ Therefore, if the arithmetics in type does not overflow, then the
+ bounds are (X - Y, X - Y), otherwise they are (X - Y - M, X - Y)
+ Similarly, if X < Y, the bounds are either (X - Y, X - Y) or
+ (X - Y, X - Y + M). */
+
+ if (rel == 0)
+ {
+ mpz_set_ui (bnds->below, 0);
+ mpz_set_ui (bnds->up, 0);
+ return;
+ }
+
+ mpz_init (m);
+ mpz_set_double_int (m, double_int_mask (TYPE_PRECISION (type)), true);
+ mpz_add_ui (m, m, 1);
+ mpz_sub (bnds->up, x, y);
+ mpz_set (bnds->below, bnds->up);
+
+ if (may_wrap)
+ {
+ if (rel > 0)
+ mpz_sub (bnds->below, bnds->below, m);
+ else
+ mpz_add (bnds->up, bnds->up, m);
+ }
+
+ mpz_clear (m);
+}
+
+/* From condition C0 CMP C1 derives information regarding the
+ difference of values of VARX + OFFX and VARY + OFFY, computed in TYPE,
+ and stores it to BNDS. */
+
+static void
+refine_bounds_using_guard (tree type, tree varx, mpz_t offx,
+ tree vary, mpz_t offy,
+ tree c0, enum tree_code cmp, tree c1,
+ bounds *bnds)
+{
+ tree varc0, varc1, tmp, ctype;
+ mpz_t offc0, offc1, loffx, loffy, bnd;
+ bool lbound = false;
+ bool no_wrap = nowrap_type_p (type);
+ bool x_ok, y_ok;
+
+ switch (cmp)
+ {
+ case LT_EXPR:
+ case LE_EXPR:
+ case GT_EXPR:
+ case GE_EXPR:
+ STRIP_SIGN_NOPS (c0);
+ STRIP_SIGN_NOPS (c1);
+ ctype = TREE_TYPE (c0);
+ if (!useless_type_conversion_p (ctype, type))
+ return;
+
+ break;
+
+ case EQ_EXPR:
+ /* We could derive quite precise information from EQ_EXPR, however, such
+ a guard is unlikely to appear, so we do not bother with handling
+ it. */
+ return;
+
+ case NE_EXPR:
+ /* NE_EXPR comparisons do not contain much of useful information, except for
+ special case of comparing with the bounds of the type. */
+ if (TREE_CODE (c1) != INTEGER_CST
+ || !INTEGRAL_TYPE_P (type))
+ return;
+
+ /* Ensure that the condition speaks about an expression in the same type
+ as X and Y. */
+ ctype = TREE_TYPE (c0);
+ if (TYPE_PRECISION (ctype) != TYPE_PRECISION (type))
+ return;
+ c0 = fold_convert (type, c0);
+ c1 = fold_convert (type, c1);
+
+ if (TYPE_MIN_VALUE (type)
+ && operand_equal_p (c1, TYPE_MIN_VALUE (type), 0))
+ {
+ cmp = GT_EXPR;
+ break;
+ }
+ if (TYPE_MAX_VALUE (type)
+ && operand_equal_p (c1, TYPE_MAX_VALUE (type), 0))
+ {
+ cmp = LT_EXPR;
+ break;
+ }
+
+ return;
+ default:
+ return;
+ }
+
+ mpz_init (offc0);
+ mpz_init (offc1);
+ split_to_var_and_offset (expand_simple_operations (c0), &varc0, offc0);
+ split_to_var_and_offset (expand_simple_operations (c1), &varc1, offc1);
+
+ /* We are only interested in comparisons of expressions based on VARX and
+ VARY. TODO -- we might also be able to derive some bounds from
+ expressions containing just one of the variables. */
+
+ if (operand_equal_p (varx, varc1, 0))
+ {
+ tmp = varc0; varc0 = varc1; varc1 = tmp;
+ mpz_swap (offc0, offc1);
+ cmp = swap_tree_comparison (cmp);
+ }
+
+ if (!operand_equal_p (varx, varc0, 0)
+ || !operand_equal_p (vary, varc1, 0))
+ goto end;
+
+ mpz_init_set (loffx, offx);
+ mpz_init_set (loffy, offy);
+
+ if (cmp == GT_EXPR || cmp == GE_EXPR)
+ {
+ tmp = varx; varx = vary; vary = tmp;
+ mpz_swap (offc0, offc1);
+ mpz_swap (loffx, loffy);
+ cmp = swap_tree_comparison (cmp);
+ lbound = true;
+ }
+
+ /* If there is no overflow, the condition implies that
+
+ (VARX + OFFX) cmp (VARY + OFFY) + (OFFX - OFFY + OFFC1 - OFFC0).
+
+ The overflows and underflows may complicate things a bit; each
+ overflow decreases the appropriate offset by M, and underflow
+ increases it by M. The above inequality would not necessarily be
+ true if
+
+ -- VARX + OFFX underflows and VARX + OFFC0 does not, or
+ VARX + OFFC0 overflows, but VARX + OFFX does not.
+ This may only happen if OFFX < OFFC0.
+ -- VARY + OFFY overflows and VARY + OFFC1 does not, or
+ VARY + OFFC1 underflows and VARY + OFFY does not.
+ This may only happen if OFFY > OFFC1. */
+
+ if (no_wrap)
+ {
+ x_ok = true;
+ y_ok = true;
+ }
+ else
+ {
+ x_ok = (integer_zerop (varx)
+ || mpz_cmp (loffx, offc0) >= 0);
+ y_ok = (integer_zerop (vary)
+ || mpz_cmp (loffy, offc1) <= 0);
+ }
+
+ if (x_ok && y_ok)
+ {
+ mpz_init (bnd);
+ mpz_sub (bnd, loffx, loffy);
+ mpz_add (bnd, bnd, offc1);
+ mpz_sub (bnd, bnd, offc0);
+
+ if (cmp == LT_EXPR)
+ mpz_sub_ui (bnd, bnd, 1);
+
+ if (lbound)
+ {
+ mpz_neg (bnd, bnd);
+ if (mpz_cmp (bnds->below, bnd) < 0)
+ mpz_set (bnds->below, bnd);
+ }
+ else
+ {
+ if (mpz_cmp (bnd, bnds->up) < 0)
+ mpz_set (bnds->up, bnd);
+ }
+ mpz_clear (bnd);
+ }
+
+ mpz_clear (loffx);
+ mpz_clear (loffy);
+end:
+ mpz_clear (offc0);
+ mpz_clear (offc1);
+}
+
+/* Stores the bounds on the value of the expression X - Y in LOOP to BNDS.
+ The subtraction is considered to be performed in arbitrary precision,
+ without overflows.
+
+ We do not attempt to be too clever regarding the value ranges of X and
+ Y; most of the time, they are just integers or ssa names offsetted by
+ integer. However, we try to use the information contained in the
+ comparisons before the loop (usually created by loop header copying). */
+
+static void
+bound_difference (struct loop *loop, tree x, tree y, bounds *bnds)
+{
+ tree type = TREE_TYPE (x);
+ tree varx, vary;
+ mpz_t offx, offy;
+ mpz_t minx, maxx, miny, maxy;
+ int cnt = 0;
+ edge e;
+ basic_block bb;
+ tree c0, c1;
+ gimple cond;
+ enum tree_code cmp;
+
+ /* Get rid of unnecessary casts, but preserve the value of
+ the expressions. */
+ STRIP_SIGN_NOPS (x);
+ STRIP_SIGN_NOPS (y);
+
+ mpz_init (bnds->below);
+ mpz_init (bnds->up);
+ mpz_init (offx);
+ mpz_init (offy);
+ split_to_var_and_offset (x, &varx, offx);
+ split_to_var_and_offset (y, &vary, offy);
+
+ if (!integer_zerop (varx)
+ && operand_equal_p (varx, vary, 0))
+ {
+ /* Special case VARX == VARY -- we just need to compare the
+ offsets. The matters are a bit more complicated in the
+ case addition of offsets may wrap. */
+ bound_difference_of_offsetted_base (type, offx, offy, bnds);
+ }
+ else
+ {
+ /* Otherwise, use the value ranges to determine the initial
+ estimates on below and up. */
+ mpz_init (minx);
+ mpz_init (maxx);
+ mpz_init (miny);
+ mpz_init (maxy);
+ determine_value_range (type, varx, offx, minx, maxx);
+ determine_value_range (type, vary, offy, miny, maxy);
+
+ mpz_sub (bnds->below, minx, maxy);
+ mpz_sub (bnds->up, maxx, miny);
+ mpz_clear (minx);
+ mpz_clear (maxx);
+ mpz_clear (miny);
+ mpz_clear (maxy);
+ }
+
+ /* If both X and Y are constants, we cannot get any more precise. */
+ if (integer_zerop (varx) && integer_zerop (vary))
+ goto end;
+
+ /* Now walk the dominators of the loop header and use the entry
+ guards to refine the estimates. */
+ for (bb = loop->header;
+ bb != ENTRY_BLOCK_PTR && cnt < MAX_DOMINATORS_TO_WALK;
+ bb = get_immediate_dominator (CDI_DOMINATORS, bb))
+ {
+ if (!single_pred_p (bb))
+ continue;
+ e = single_pred_edge (bb);
+
+ if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
+ continue;
- return (TREE_INT_CST_LOW (arg) != 0 || TREE_INT_CST_HIGH (arg) != 0);
+ cond = last_stmt (e->src);
+ c0 = gimple_cond_lhs (cond);
+ cmp = gimple_cond_code (cond);
+ c1 = gimple_cond_rhs (cond);
+
+ if (e->flags & EDGE_FALSE_VALUE)
+ cmp = invert_tree_comparison (cmp, false);
+
+ refine_bounds_using_guard (type, varx, offx, vary, offy,
+ c0, cmp, c1, bnds);
+ ++cnt;
+ }
+
+end:
+ mpz_clear (offx);
+ mpz_clear (offy);
+}
+
+/* Update the bounds in BNDS that restrict the value of X to the bounds
+ that restrict the value of X + DELTA. X can be obtained as a
+ difference of two values in TYPE. */
+
+static void
+bounds_add (bounds *bnds, double_int delta, tree type)
+{
+ mpz_t mdelta, max;
+
+ mpz_init (mdelta);
+ mpz_set_double_int (mdelta, delta, false);
+
+ mpz_init (max);
+ mpz_set_double_int (max, double_int_mask (TYPE_PRECISION (type)), true);
+
+ mpz_add (bnds->up, bnds->up, mdelta);
+ mpz_add (bnds->below, bnds->below, mdelta);
+
+ if (mpz_cmp (bnds->up, max) > 0)
+ mpz_set (bnds->up, max);
+
+ mpz_neg (max, max);
+ if (mpz_cmp (bnds->below, max) < 0)
+ mpz_set (bnds->below, max);
+
+ mpz_clear (mdelta);
+ mpz_clear (max);
+}
+
+/* Update the bounds in BNDS that restrict the value of X to the bounds
+ that restrict the value of -X. */
+
+static void
+bounds_negate (bounds *bnds)
+{
+ mpz_t tmp;
+
+ mpz_init_set (tmp, bnds->up);
+ mpz_neg (bnds->up, bnds->below);
+ mpz_neg (bnds->below, tmp);
+ mpz_clear (tmp);
}
/* Returns inverse of X modulo 2^s, where MASK = 2^s-1. */
}
else
{
- rslt = build_int_cst_type (type, 1);
+ rslt = build_int_cst (type, 1);
for (; ctr; ctr--)
{
- rslt = fold_binary_to_constant (MULT_EXPR, type, rslt, x);
- x = fold_binary_to_constant (MULT_EXPR, type, x, x);
+ rslt = int_const_binop (MULT_EXPR, rslt, x, 0);
+ x = int_const_binop (MULT_EXPR, x, x, 0);
}
- rslt = fold_binary_to_constant (BIT_AND_EXPR, type, rslt, mask);
+ rslt = int_const_binop (BIT_AND_EXPR, rslt, mask, 0);
}
return rslt;
}
-/* Determine the number of iterations according to condition (for staying
- inside loop) which compares two induction variables using comparison
- operator CODE. The induction variable on left side of the comparison
- has base BASE0 and step STEP0. the right-hand side one has base
- BASE1 and step STEP1. Both induction variables must have type TYPE,
- which must be an integer or pointer type. STEP0 and STEP1 must be
- constants (or NULL_TREE, which is interpreted as constant zero).
-
- The results (number of iterations and assumptions as described in
- comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
- In case we are unable to determine number of iterations, contents of
- this structure is unchanged. */
+/* Derives the upper bound BND on the number of executions of loop with exit
+ condition S * i <> C, assuming that the loop is not infinite. If
+ NO_OVERFLOW is true, then the control variable of the loop does not
+ overflow. If NO_OVERFLOW is true or BNDS.below >= 0, then BNDS.up
+ contains the upper bound on the value of C. */
static void
-number_of_iterations_cond (tree type, tree base0, tree step0,
- enum tree_code code, tree base1, tree step1,
- struct tree_niter_desc *niter)
+number_of_iterations_ne_max (mpz_t bnd, bool no_overflow, tree c, tree s,
+ bounds *bnds)
{
- tree step, delta, mmin, mmax;
- tree may_xform, bound, s, d, tmp;
- bool was_sharp = false;
- tree assumption;
- tree assumptions = boolean_true_node;
- tree noloop_assumptions = boolean_false_node;
- tree niter_type, signed_niter_type;
- tree bits;
-
- /* The meaning of these assumptions is this:
- if !assumptions
- then the rest of information does not have to be valid
- if noloop_assumptions then the loop does not have to roll
- (but it is only conservative approximation, i.e. it only says that
- if !noloop_assumptions, then the loop does not end before the computed
- number of iterations) */
-
- /* Make < comparison from > ones. */
- if (code == GE_EXPR
- || code == GT_EXPR)
- {
- SWAP (base0, base1);
- SWAP (step0, step1);
- code = swap_tree_comparison (code);
- }
+ double_int max;
+ mpz_t d;
- /* We can handle the case when neither of the sides of the comparison is
- invariant, provided that the test is NE_EXPR. This rarely occurs in
- practice, but it is simple enough to manage. */
- if (!zero_p (step0) && !zero_p (step1))
+ /* If the control variable does not overflow, the number of iterations is
+ at most c / s. Otherwise it is at most the period of the control
+ variable. */
+ if (!no_overflow && !multiple_of_p (TREE_TYPE (c), c, s))
{
- if (code != NE_EXPR)
- return;
-
- step0 = fold_binary_to_constant (MINUS_EXPR, type, step0, step1);
- step1 = NULL_TREE;
+ max = double_int_mask (TYPE_PRECISION (TREE_TYPE (c))
+ - tree_low_cst (num_ending_zeros (s), 1));
+ mpz_set_double_int (bnd, max, true);
+ return;
}
- /* If the result is a constant, the loop is weird. More precise handling
- would be possible, but the situation is not common enough to waste time
- on it. */
- if (zero_p (step0) && zero_p (step1))
- return;
+ /* Determine the upper bound on C. */
+ if (no_overflow || mpz_sgn (bnds->below) >= 0)
+ mpz_set (bnd, bnds->up);
+ else if (TREE_CODE (c) == INTEGER_CST)
+ mpz_set_double_int (bnd, tree_to_double_int (c), true);
+ else
+ mpz_set_double_int (bnd, double_int_mask (TYPE_PRECISION (TREE_TYPE (c))),
+ true);
- /* Ignore loops of while (i-- < 10) type. */
- if (code != NE_EXPR)
- {
- if (step0 && !tree_expr_nonnegative_p (step0))
- return;
+ mpz_init (d);
+ mpz_set_double_int (d, tree_to_double_int (s), true);
+ mpz_fdiv_q (bnd, bnd, d);
+ mpz_clear (d);
+}
- if (!zero_p (step1) && tree_expr_nonnegative_p (step1))
- return;
- }
+/* Determines number of iterations of loop whose ending condition
+ is IV <> FINAL. TYPE is the type of the iv. The number of
+ iterations is stored to NITER. NEVER_INFINITE is true if
+ we know that the exit must be taken eventually, i.e., that the IV
+ ever reaches the value FINAL (we derived this earlier, and possibly set
+ NITER->assumptions to make sure this is the case). BNDS contains the
+ bounds on the difference FINAL - IV->base. */
- if (POINTER_TYPE_P (type))
+static bool
+number_of_iterations_ne (tree type, affine_iv *iv, tree final,
+ struct tree_niter_desc *niter, bool never_infinite,
+ bounds *bnds)
+{
+ tree niter_type = unsigned_type_for (type);
+ tree s, c, d, bits, assumption, tmp, bound;
+ mpz_t max;
+
+ niter->control = *iv;
+ niter->bound = final;
+ niter->cmp = NE_EXPR;
+
+ /* Rearrange the terms so that we get inequality S * i <> C, with S
+ positive. Also cast everything to the unsigned type. If IV does
+ not overflow, BNDS bounds the value of C. Also, this is the
+ case if the computation |FINAL - IV->base| does not overflow, i.e.,
+ if BNDS->below in the result is nonnegative. */
+ if (tree_int_cst_sign_bit (iv->step))
{
- /* We assume pointer arithmetic never overflows. */
- mmin = mmax = NULL_TREE;
+ s = fold_convert (niter_type,
+ fold_build1 (NEGATE_EXPR, type, iv->step));
+ c = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, iv->base),
+ fold_convert (niter_type, final));
+ bounds_negate (bnds);
}
else
{
- mmin = TYPE_MIN_VALUE (type);
- mmax = TYPE_MAX_VALUE (type);
+ s = fold_convert (niter_type, iv->step);
+ c = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, final),
+ fold_convert (niter_type, iv->base));
}
- /* Some more condition normalization. We must record some assumptions
- due to overflows. */
+ mpz_init (max);
+ number_of_iterations_ne_max (max, iv->no_overflow, c, s, bnds);
+ niter->max = mpz_get_double_int (niter_type, max, false);
+ mpz_clear (max);
- if (code == LT_EXPR)
+ /* First the trivial cases -- when the step is 1. */
+ if (integer_onep (s))
{
- /* We want to take care only of <=; this is easy,
- as in cases the overflow would make the transformation unsafe the loop
- does not roll. Seemingly it would make more sense to want to take
- care of <, as NE is more similar to it, but the problem is that here
- the transformation would be more difficult due to possibly infinite
- loops. */
- if (zero_p (step0))
- {
- if (mmax)
- assumption = fold_build2 (EQ_EXPR, boolean_type_node, base0, mmax);
- else
- assumption = boolean_false_node;
- if (nonzero_p (assumption))
- goto zero_iter;
- base0 = fold_build2 (PLUS_EXPR, type, base0,
- build_int_cst_type (type, 1));
- }
- else
- {
- if (mmin)
- assumption = fold_build2 (EQ_EXPR, boolean_type_node, base1, mmin);
- else
- assumption = boolean_false_node;
- if (nonzero_p (assumption))
- goto zero_iter;
- base1 = fold_build2 (MINUS_EXPR, type, base1,
- build_int_cst_type (type, 1));
- }
- noloop_assumptions = assumption;
- code = LE_EXPR;
-
- /* It will be useful to be able to tell the difference once more in
- <= -> != reduction. */
- was_sharp = true;
+ niter->niter = c;
+ return true;
}
- /* Take care of trivially infinite loops. */
- if (code != NE_EXPR)
- {
- if (zero_p (step0)
- && mmin
- && operand_equal_p (base0, mmin, 0))
- return;
- if (zero_p (step1)
- && mmax
- && operand_equal_p (base1, mmax, 0))
- return;
- }
+ /* Let nsd (step, size of mode) = d. If d does not divide c, the loop
+ is infinite. Otherwise, the number of iterations is
+ (inverse(s/d) * (c/d)) mod (size of mode/d). */
+ bits = num_ending_zeros (s);
+ bound = build_low_bits_mask (niter_type,
+ (TYPE_PRECISION (niter_type)
+ - tree_low_cst (bits, 1)));
- /* If we can we want to take care of NE conditions instead of size
- comparisons, as they are much more friendly (most importantly
- this takes care of special handling of loops with step 1). We can
- do it if we first check that upper bound is greater or equal to
- lower bound, their difference is constant c modulo step and that
- there is not an overflow. */
- if (code != NE_EXPR)
- {
- if (zero_p (step0))
- step = fold_unary_to_constant (NEGATE_EXPR, type, step1);
- else
- step = step0;
- delta = build2 (MINUS_EXPR, type, base1, base0);
- delta = fold_build2 (FLOOR_MOD_EXPR, type, delta, step);
- may_xform = boolean_false_node;
+ d = fold_binary_to_constant (LSHIFT_EXPR, niter_type,
+ build_int_cst (niter_type, 1), bits);
+ s = fold_binary_to_constant (RSHIFT_EXPR, niter_type, s, bits);
- if (TREE_CODE (delta) == INTEGER_CST)
- {
- tmp = fold_binary_to_constant (MINUS_EXPR, type, step,
- build_int_cst_type (type, 1));
- if (was_sharp
- && operand_equal_p (delta, tmp, 0))
- {
- /* A special case. We have transformed condition of type
- for (i = 0; i < 4; i += 4)
- into
- for (i = 0; i <= 3; i += 4)
- obviously if the test for overflow during that transformation
- passed, we cannot overflow here. Most importantly any
- loop with sharp end condition and step 1 falls into this
- category, so handling this case specially is definitely
- worth the troubles. */
- may_xform = boolean_true_node;
- }
- else if (zero_p (step0))
- {
- if (!mmin)
- may_xform = boolean_true_node;
- else
- {
- bound = fold_binary_to_constant (PLUS_EXPR, type,
- mmin, step);
- bound = fold_binary_to_constant (MINUS_EXPR, type,
- bound, delta);
- may_xform = fold_build2 (LE_EXPR, boolean_type_node,
- bound, base0);
- }
- }
- else
- {
- if (!mmax)
- may_xform = boolean_true_node;
- else
- {
- bound = fold_binary_to_constant (MINUS_EXPR, type,
- mmax, step);
- bound = fold_binary_to_constant (PLUS_EXPR, type,
- bound, delta);
- may_xform = fold_build2 (LE_EXPR, boolean_type_node,
- base1, bound);
- }
- }
- }
+ if (!never_infinite)
+ {
+ /* If we cannot assume that the loop is not infinite, record the
+ assumptions for divisibility of c. */
+ assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, c, d);
+ assumption = fold_build2 (EQ_EXPR, boolean_type_node,
+ assumption, build_int_cst (niter_type, 0));
+ if (!integer_nonzerop (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+ }
+
+ c = fold_build2 (EXACT_DIV_EXPR, niter_type, c, d);
+ tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound));
+ niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
+ return true;
+}
- if (!zero_p (may_xform))
- {
- /* We perform the transformation always provided that it is not
- completely senseless. This is OK, as we would need this assumption
- to determine the number of iterations anyway. */
- if (!nonzero_p (may_xform))
- assumptions = may_xform;
+/* Checks whether we can determine the final value of the control variable
+ of the loop with ending condition IV0 < IV1 (computed in TYPE).
+ DELTA is the difference IV1->base - IV0->base, STEP is the absolute value
+ of the step. The assumptions necessary to ensure that the computation
+ of the final value does not overflow are recorded in NITER. If we
+ find the final value, we adjust DELTA and return TRUE. Otherwise
+ we return false. BNDS bounds the value of IV1->base - IV0->base,
+ and will be updated by the same amount as DELTA. */
- if (zero_p (step0))
- {
- base0 = fold_build2 (PLUS_EXPR, type, base0, delta);
- base0 = fold_build2 (MINUS_EXPR, type, base0, step);
- }
- else
- {
- base1 = fold_build2 (MINUS_EXPR, type, base1, delta);
- base1 = fold_build2 (PLUS_EXPR, type, base1, step);
- }
+static bool
+number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter,
+ tree *delta, tree step,
+ bounds *bnds)
+{
+ tree niter_type = TREE_TYPE (step);
+ tree mod = fold_build2 (FLOOR_MOD_EXPR, niter_type, *delta, step);
+ tree tmod;
+ mpz_t mmod;
+ tree assumption = boolean_true_node, bound, noloop;
+ bool ret = false;
+ tree type1 = type;
+ if (POINTER_TYPE_P (type))
+ type1 = sizetype;
- assumption = fold_build2 (GT_EXPR, boolean_type_node, base0, base1);
- noloop_assumptions = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- noloop_assumptions, assumption);
- code = NE_EXPR;
- }
- }
+ if (TREE_CODE (mod) != INTEGER_CST)
+ return false;
+ if (integer_nonzerop (mod))
+ mod = fold_build2 (MINUS_EXPR, niter_type, step, mod);
+ tmod = fold_convert (type1, mod);
- /* Count the number of iterations. */
- niter_type = unsigned_type_for (type);
- signed_niter_type = signed_type_for (type);
+ mpz_init (mmod);
+ mpz_set_double_int (mmod, tree_to_double_int (mod), true);
+ mpz_neg (mmod, mmod);
- if (code == NE_EXPR)
+ if (integer_nonzerop (iv0->step))
{
- /* Everything we do here is just arithmetics modulo size of mode. This
- makes us able to do more involved computations of number of iterations
- than in other cases. First transform the condition into shape
- s * i <> c, with s positive. */
- base1 = fold_build2 (MINUS_EXPR, type, base1, base0);
- base0 = NULL_TREE;
- if (!zero_p (step1))
- step0 = fold_unary_to_constant (NEGATE_EXPR, type, step1);
- step1 = NULL_TREE;
- if (!tree_expr_nonnegative_p (fold_convert (signed_niter_type, step0)))
+ /* The final value of the iv is iv1->base + MOD, assuming that this
+ computation does not overflow, and that
+ iv0->base <= iv1->base + MOD. */
+ if (!iv0->no_overflow && !integer_zerop (mod))
{
- step0 = fold_unary_to_constant (NEGATE_EXPR, type, step0);
- base1 = fold_build1 (NEGATE_EXPR, type, base1);
+ bound = fold_build2 (MINUS_EXPR, type1,
+ TYPE_MAX_VALUE (type1), tmod);
+ if (POINTER_TYPE_P (type))
+ bound = fold_convert (type, bound);
+ assumption = fold_build2 (LE_EXPR, boolean_type_node,
+ iv1->base, bound);
+ if (integer_zerop (assumption))
+ goto end;
}
-
- base1 = fold_convert (niter_type, base1);
- step0 = fold_convert (niter_type, step0);
-
- /* Let nsd (step, size of mode) = d. If d does not divide c, the loop
- is infinite. Otherwise, the number of iterations is
- (inverse(s/d) * (c/d)) mod (size of mode/d). */
- bits = num_ending_zeros (step0);
- d = fold_binary_to_constant (LSHIFT_EXPR, niter_type,
- build_int_cst_type (niter_type, 1), bits);
- s = fold_binary_to_constant (RSHIFT_EXPR, niter_type, step0, bits);
-
- bound = build_low_bits_mask (niter_type,
- (TYPE_PRECISION (niter_type)
- - tree_low_cst (bits, 1)));
-
- assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, base1, d);
- assumption = fold_build2 (EQ_EXPR, boolean_type_node,
- assumption,
- build_int_cst (niter_type, 0));
- assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
- assumptions, assumption);
-
- tmp = fold_build2 (EXACT_DIV_EXPR, niter_type, base1, d);
- tmp = fold_build2 (MULT_EXPR, niter_type, tmp, inverse (s, bound));
- niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
+ if (mpz_cmp (mmod, bnds->below) < 0)
+ noloop = boolean_false_node;
+ else if (POINTER_TYPE_P (type))
+ noloop = fold_build2 (GT_EXPR, boolean_type_node,
+ iv0->base,
+ fold_build2 (POINTER_PLUS_EXPR, type,
+ iv1->base, tmod));
+ else
+ noloop = fold_build2 (GT_EXPR, boolean_type_node,
+ iv0->base,
+ fold_build2 (PLUS_EXPR, type1,
+ iv1->base, tmod));
}
else
{
- if (zero_p (step1))
- /* Condition in shape a + s * i <= b
- We must know that b + s does not overflow and a <= b + s and then we
- can compute number of iterations as (b + s - a) / s. (It might
- seem that we in fact could be more clever about testing the b + s
- overflow condition using some information about b - a mod s,
- but it was already taken into account during LE -> NE transform). */
+ /* The final value of the iv is iv0->base - MOD, assuming that this
+ computation does not overflow, and that
+ iv0->base - MOD <= iv1->base. */
+ if (!iv1->no_overflow && !integer_zerop (mod))
{
- if (mmax)
- {
- bound = fold_binary_to_constant (MINUS_EXPR, type, mmax, step0);
- assumption = fold_build2 (LE_EXPR, boolean_type_node,
- base1, bound);
- assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
- assumptions, assumption);
- }
-
- step = step0;
- tmp = fold_build2 (PLUS_EXPR, type, base1, step0);
- assumption = fold_build2 (GT_EXPR, boolean_type_node, base0, tmp);
- delta = fold_build2 (PLUS_EXPR, type, base1, step);
- delta = fold_build2 (MINUS_EXPR, type, delta, base0);
- delta = fold_convert (niter_type, delta);
+ bound = fold_build2 (PLUS_EXPR, type1,
+ TYPE_MIN_VALUE (type1), tmod);
+ if (POINTER_TYPE_P (type))
+ bound = fold_convert (type, bound);
+ assumption = fold_build2 (GE_EXPR, boolean_type_node,
+ iv0->base, bound);
+ if (integer_zerop (assumption))
+ goto end;
}
+ if (mpz_cmp (mmod, bnds->below) < 0)
+ noloop = boolean_false_node;
+ else if (POINTER_TYPE_P (type))
+ noloop = fold_build2 (GT_EXPR, boolean_type_node,
+ fold_build2 (POINTER_PLUS_EXPR, type,
+ iv0->base,
+ fold_build1 (NEGATE_EXPR,
+ type1, tmod)),
+ iv1->base);
else
- {
- /* Condition in shape a <= b - s * i
- We must know that a - s does not overflow and a - s <= b and then
- we can again compute number of iterations as (b - (a - s)) / s. */
- if (mmin)
- {
- bound = fold_binary_to_constant (MINUS_EXPR, type, mmin, step1);
- assumption = fold_build2 (LE_EXPR, boolean_type_node,
- bound, base0);
- assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
- assumptions, assumption);
- }
- step = fold_build1 (NEGATE_EXPR, type, step1);
- tmp = fold_build2 (PLUS_EXPR, type, base0, step1);
- assumption = fold_build2 (GT_EXPR, boolean_type_node, tmp, base1);
- delta = fold_build2 (MINUS_EXPR, type, base0, step);
- delta = fold_build2 (MINUS_EXPR, type, base1, delta);
- delta = fold_convert (niter_type, delta);
- }
- noloop_assumptions = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- noloop_assumptions, assumption);
- delta = fold_build2 (FLOOR_DIV_EXPR, niter_type, delta,
- fold_convert (niter_type, step));
- niter->niter = delta;
+ noloop = fold_build2 (GT_EXPR, boolean_type_node,
+ fold_build2 (MINUS_EXPR, type1,
+ iv0->base, tmod),
+ iv1->base);
}
- niter->assumptions = assumptions;
- niter->may_be_zero = noloop_assumptions;
- return;
-
-zero_iter:
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_true_node;
- niter->niter = build_int_cst_type (type, 0);
- return;
+ if (!integer_nonzerop (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions,
+ assumption);
+ if (!integer_zerop (noloop))
+ niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
+ niter->may_be_zero,
+ noloop);
+ bounds_add (bnds, tree_to_double_int (mod), type);
+ *delta = fold_build2 (PLUS_EXPR, niter_type, *delta, mod);
+
+ ret = true;
+end:
+ mpz_clear (mmod);
+ return ret;
}
-
-/* Similar to number_of_iterations_cond, but only handles the special
- case of loops with step 1 or -1. The meaning of the arguments
- is the same as in number_of_iterations_cond. The function
- returns true if the special case was recognized, false otherwise. */
+/* Add assertions to NITER that ensure that the control variable of the loop
+ with ending condition IV0 < IV1 does not overflow. Types of IV0 and IV1
+ are TYPE. Returns false if we can prove that there is an overflow, true
+ otherwise. STEP is the absolute value of the step. */
static bool
-number_of_iterations_special (tree type, tree base0, tree step0,
- enum tree_code code, tree base1, tree step1,
- struct tree_niter_desc *niter)
+assert_no_overflow_lt (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter, tree step)
{
- tree niter_type = unsigned_type_for (type), mmax, mmin;
+ tree bound, d, assumption, diff;
+ tree niter_type = TREE_TYPE (step);
- /* Make < comparison from > ones. */
- if (code == GE_EXPR
- || code == GT_EXPR)
+ if (integer_nonzerop (iv0->step))
{
- SWAP (base0, base1);
- SWAP (step0, step1);
- code = swap_tree_comparison (code);
- }
+ /* for (i = iv0->base; i < iv1->base; i += iv0->step) */
+ if (iv0->no_overflow)
+ return true;
- switch (code)
- {
- case NE_EXPR:
- if (zero_p (step0))
+ /* If iv0->base is a constant, we can determine the last value before
+ overflow precisely; otherwise we conservatively assume
+ MAX - STEP + 1. */
+
+ if (TREE_CODE (iv0->base) == INTEGER_CST)
{
- if (zero_p (step1))
- return false;
- SWAP (base0, base1);
- SWAP (step0, step1);
+ d = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, TYPE_MAX_VALUE (type)),
+ fold_convert (niter_type, iv0->base));
+ diff = fold_build2 (FLOOR_MOD_EXPR, niter_type, d, step);
}
- else if (!zero_p (step1))
- return false;
+ else
+ diff = fold_build2 (MINUS_EXPR, niter_type, step,
+ build_int_cst (niter_type, 1));
+ bound = fold_build2 (MINUS_EXPR, type,
+ TYPE_MAX_VALUE (type), fold_convert (type, diff));
+ assumption = fold_build2 (LE_EXPR, boolean_type_node,
+ iv1->base, bound);
+ }
+ else
+ {
+ /* for (i = iv1->base; i > iv0->base; i += iv1->step) */
+ if (iv1->no_overflow)
+ return true;
- if (integer_onep (step0))
+ if (TREE_CODE (iv1->base) == INTEGER_CST)
{
- /* for (i = base0; i != base1; i++) */
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_false_node;
- niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
- niter->additional_info = boolean_true_node;
- }
- else if (integer_all_onesp (step0))
- {
- /* for (i = base0; i != base1; i--) */
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_false_node;
- niter->niter = fold_build2 (MINUS_EXPR, type, base0, base1);
+ d = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, iv1->base),
+ fold_convert (niter_type, TYPE_MIN_VALUE (type)));
+ diff = fold_build2 (FLOOR_MOD_EXPR, niter_type, d, step);
}
else
- return false;
+ diff = fold_build2 (MINUS_EXPR, niter_type, step,
+ build_int_cst (niter_type, 1));
+ bound = fold_build2 (PLUS_EXPR, type,
+ TYPE_MIN_VALUE (type), fold_convert (type, diff));
+ assumption = fold_build2 (GE_EXPR, boolean_type_node,
+ iv0->base, bound);
+ }
- break;
+ if (integer_zerop (assumption))
+ return false;
+ if (!integer_nonzerop (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+
+ iv0->no_overflow = true;
+ iv1->no_overflow = true;
+ return true;
+}
- case LT_EXPR:
- if ((step0 && integer_onep (step0) && zero_p (step1))
- || (step1 && integer_all_onesp (step1) && zero_p (step0)))
+/* Add an assumption to NITER that a loop whose ending condition
+ is IV0 < IV1 rolls. TYPE is the type of the control iv. BNDS
+ bounds the value of IV1->base - IV0->base. */
+
+static void
+assert_loop_rolls_lt (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter, bounds *bnds)
+{
+ tree assumption = boolean_true_node, bound, diff;
+ tree mbz, mbzl, mbzr, type1;
+ bool rolls_p, no_overflow_p;
+ double_int dstep;
+ mpz_t mstep, max;
+
+ /* We are going to compute the number of iterations as
+ (iv1->base - iv0->base + step - 1) / step, computed in the unsigned
+ variant of TYPE. This formula only works if
+
+ -step + 1 <= (iv1->base - iv0->base) <= MAX - step + 1
+
+ (where MAX is the maximum value of the unsigned variant of TYPE, and
+ the computations in this formula are performed in full precision
+ (without overflows).
+
+ Usually, for loops with exit condition iv0->base + step * i < iv1->base,
+ we have a condition of form iv0->base - step < iv1->base before the loop,
+ and for loops iv0->base < iv1->base - step * i the condition
+ iv0->base < iv1->base + step, due to loop header copying, which enable us
+ to prove the lower bound.
+
+ The upper bound is more complicated. Unless the expressions for initial
+ and final value themselves contain enough information, we usually cannot
+ derive it from the context. */
+
+ /* First check whether the answer does not follow from the bounds we gathered
+ before. */
+ if (integer_nonzerop (iv0->step))
+ dstep = tree_to_double_int (iv0->step);
+ else
+ {
+ dstep = double_int_sext (tree_to_double_int (iv1->step),
+ TYPE_PRECISION (type));
+ dstep = double_int_neg (dstep);
+ }
+
+ mpz_init (mstep);
+ mpz_set_double_int (mstep, dstep, true);
+ mpz_neg (mstep, mstep);
+ mpz_add_ui (mstep, mstep, 1);
+
+ rolls_p = mpz_cmp (mstep, bnds->below) <= 0;
+
+ mpz_init (max);
+ mpz_set_double_int (max, double_int_mask (TYPE_PRECISION (type)), true);
+ mpz_add (max, max, mstep);
+ no_overflow_p = (mpz_cmp (bnds->up, max) <= 0
+ /* For pointers, only values lying inside a single object
+ can be compared or manipulated by pointer arithmetics.
+ Gcc in general does not allow or handle objects larger
+ than half of the address space, hence the upper bound
+ is satisfied for pointers. */
+ || POINTER_TYPE_P (type));
+ mpz_clear (mstep);
+ mpz_clear (max);
+
+ if (rolls_p && no_overflow_p)
+ return;
+
+ type1 = type;
+ if (POINTER_TYPE_P (type))
+ type1 = sizetype;
+
+ /* Now the hard part; we must formulate the assumption(s) as expressions, and
+ we must be careful not to introduce overflow. */
+
+ if (integer_nonzerop (iv0->step))
+ {
+ diff = fold_build2 (MINUS_EXPR, type1,
+ iv0->step, build_int_cst (type1, 1));
+
+ /* We need to know that iv0->base >= MIN + iv0->step - 1. Since
+ 0 address never belongs to any object, we can assume this for
+ pointers. */
+ if (!POINTER_TYPE_P (type))
{
- /* for (i = base0; i < base1; i++)
-
- or
+ bound = fold_build2 (PLUS_EXPR, type1,
+ TYPE_MIN_VALUE (type), diff);
+ assumption = fold_build2 (GE_EXPR, boolean_type_node,
+ iv0->base, bound);
+ }
- for (i = base1; i > base0; i--).
-
- In both cases # of iterations is base1 - base0. */
+ /* And then we can compute iv0->base - diff, and compare it with
+ iv1->base. */
+ mbzl = fold_build2 (MINUS_EXPR, type1,
+ fold_convert (type1, iv0->base), diff);
+ mbzr = fold_convert (type1, iv1->base);
+ }
+ else
+ {
+ diff = fold_build2 (PLUS_EXPR, type1,
+ iv1->step, build_int_cst (type1, 1));
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
- base0, base1);
- niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
+ if (!POINTER_TYPE_P (type))
+ {
+ bound = fold_build2 (PLUS_EXPR, type1,
+ TYPE_MAX_VALUE (type), diff);
+ assumption = fold_build2 (LE_EXPR, boolean_type_node,
+ iv1->base, bound);
}
+
+ mbzl = fold_convert (type1, iv0->base);
+ mbzr = fold_build2 (MINUS_EXPR, type1,
+ fold_convert (type1, iv1->base), diff);
+ }
+
+ if (!integer_nonzerop (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+ if (!rolls_p)
+ {
+ mbz = fold_build2 (GT_EXPR, boolean_type_node, mbzl, mbzr);
+ niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
+ niter->may_be_zero, mbz);
+ }
+}
+
+/* Determines number of iterations of loop whose ending condition
+ is IV0 < IV1. TYPE is the type of the iv. The number of
+ iterations is stored to NITER. BNDS bounds the difference
+ IV1->base - IV0->base. */
+
+static bool
+number_of_iterations_lt (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter,
+ bool never_infinite ATTRIBUTE_UNUSED,
+ bounds *bnds)
+{
+ tree niter_type = unsigned_type_for (type);
+ tree delta, step, s;
+ mpz_t mstep, tmp;
+
+ if (integer_nonzerop (iv0->step))
+ {
+ niter->control = *iv0;
+ niter->cmp = LT_EXPR;
+ niter->bound = iv1->base;
+ }
+ else
+ {
+ niter->control = *iv1;
+ niter->cmp = GT_EXPR;
+ niter->bound = iv0->base;
+ }
+
+ delta = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, iv1->base),
+ fold_convert (niter_type, iv0->base));
+
+ /* First handle the special case that the step is +-1. */
+ if ((integer_onep (iv0->step) && integer_zerop (iv1->step))
+ || (integer_all_onesp (iv1->step) && integer_zerop (iv0->step)))
+ {
+ /* for (i = iv0->base; i < iv1->base; i++)
+
+ or
+
+ for (i = iv1->base; i > iv0->base; i--).
+
+ In both cases # of iterations is iv1->base - iv0->base, assuming that
+ iv1->base >= iv0->base.
+
+ First try to derive a lower bound on the value of
+ iv1->base - iv0->base, computed in full precision. If the difference
+ is nonnegative, we are done, otherwise we must record the
+ condition. */
+
+ if (mpz_sgn (bnds->below) < 0)
+ niter->may_be_zero = fold_build2 (LT_EXPR, boolean_type_node,
+ iv1->base, iv0->base);
+ niter->niter = delta;
+ niter->max = mpz_get_double_int (niter_type, bnds->up, false);
+ return true;
+ }
+
+ if (integer_nonzerop (iv0->step))
+ step = fold_convert (niter_type, iv0->step);
+ else
+ step = fold_convert (niter_type,
+ fold_build1 (NEGATE_EXPR, type, iv1->step));
+
+ /* If we can determine the final value of the control iv exactly, we can
+ transform the condition to != comparison. In particular, this will be
+ the case if DELTA is constant. */
+ if (number_of_iterations_lt_to_ne (type, iv0, iv1, niter, &delta, step,
+ bnds))
+ {
+ affine_iv zps;
+
+ zps.base = build_int_cst (niter_type, 0);
+ zps.step = step;
+ /* number_of_iterations_lt_to_ne will add assumptions that ensure that
+ zps does not overflow. */
+ zps.no_overflow = true;
+
+ return number_of_iterations_ne (type, &zps, delta, niter, true, bnds);
+ }
+
+ /* Make sure that the control iv does not overflow. */
+ if (!assert_no_overflow_lt (type, iv0, iv1, niter, step))
+ return false;
+
+ /* We determine the number of iterations as (delta + step - 1) / step. For
+ this to work, we must know that iv1->base >= iv0->base - step + 1,
+ otherwise the loop does not roll. */
+ assert_loop_rolls_lt (type, iv0, iv1, niter, bnds);
+
+ s = fold_build2 (MINUS_EXPR, niter_type,
+ step, build_int_cst (niter_type, 1));
+ delta = fold_build2 (PLUS_EXPR, niter_type, delta, s);
+ niter->niter = fold_build2 (FLOOR_DIV_EXPR, niter_type, delta, step);
+
+ mpz_init (mstep);
+ mpz_init (tmp);
+ mpz_set_double_int (mstep, tree_to_double_int (step), true);
+ mpz_add (tmp, bnds->up, mstep);
+ mpz_sub_ui (tmp, tmp, 1);
+ mpz_fdiv_q (tmp, tmp, mstep);
+ niter->max = mpz_get_double_int (niter_type, tmp, false);
+ mpz_clear (mstep);
+ mpz_clear (tmp);
+
+ return true;
+}
+
+/* Determines number of iterations of loop whose ending condition
+ is IV0 <= IV1. TYPE is the type of the iv. The number of
+ iterations is stored to NITER. NEVER_INFINITE is true if
+ we know that this condition must eventually become false (we derived this
+ earlier, and possibly set NITER->assumptions to make sure this
+ is the case). BNDS bounds the difference IV1->base - IV0->base. */
+
+static bool
+number_of_iterations_le (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter, bool never_infinite,
+ bounds *bnds)
+{
+ tree assumption;
+ tree type1 = type;
+ if (POINTER_TYPE_P (type))
+ type1 = sizetype;
+
+ /* Say that IV0 is the control variable. Then IV0 <= IV1 iff
+ IV0 < IV1 + 1, assuming that IV1 is not equal to the greatest
+ value of the type. This we must know anyway, since if it is
+ equal to this value, the loop rolls forever. */
+
+ if (!never_infinite)
+ {
+ if (integer_nonzerop (iv0->step))
+ assumption = fold_build2 (NE_EXPR, boolean_type_node,
+ iv1->base, TYPE_MAX_VALUE (type));
else
+ assumption = fold_build2 (NE_EXPR, boolean_type_node,
+ iv0->base, TYPE_MIN_VALUE (type));
+
+ if (integer_zerop (assumption))
return false;
- break;
+ if (!integer_nonzerop (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+ }
- case LE_EXPR:
+ if (integer_nonzerop (iv0->step))
+ {
if (POINTER_TYPE_P (type))
- {
- /* We assume pointer arithmetic never overflows. */
- mmin = mmax = NULL_TREE;
- }
+ iv1->base = fold_build2 (POINTER_PLUS_EXPR, type, iv1->base,
+ build_int_cst (type1, 1));
else
- {
- mmin = TYPE_MIN_VALUE (type);
- mmax = TYPE_MAX_VALUE (type);
- }
+ iv1->base = fold_build2 (PLUS_EXPR, type1, iv1->base,
+ build_int_cst (type1, 1));
+ }
+ else if (POINTER_TYPE_P (type))
+ iv0->base = fold_build2 (POINTER_PLUS_EXPR, type, iv0->base,
+ fold_build1 (NEGATE_EXPR, type1,
+ build_int_cst (type1, 1)));
+ else
+ iv0->base = fold_build2 (MINUS_EXPR, type1,
+ iv0->base, build_int_cst (type1, 1));
- if (step0 && integer_onep (step0) && zero_p (step1))
- {
- /* for (i = base0; i <= base1; i++) */
- if (mmax)
- niter->assumptions = fold_build2 (NE_EXPR, boolean_type_node,
- base1, mmax);
- else
- niter->assumptions = boolean_true_node;
- base1 = fold_build2 (PLUS_EXPR, type, base1,
- build_int_cst_type (type, 1));
- }
- else if (step1 && integer_all_onesp (step1) && zero_p (step0))
- {
- /* for (i = base1; i >= base0; i--) */
- if (mmin)
- niter->assumptions = fold_build2 (NE_EXPR, boolean_type_node,
- base0, mmin);
- else
- niter->assumptions = boolean_true_node;
- base0 = fold_build2 (MINUS_EXPR, type, base0,
- build_int_cst_type (type, 1));
- }
- else
+ bounds_add (bnds, double_int_one, type1);
+
+ return number_of_iterations_lt (type, iv0, iv1, niter, never_infinite, bnds);
+}
+
+/* Dumps description of affine induction variable IV to FILE. */
+
+static void
+dump_affine_iv (FILE *file, affine_iv *iv)
+{
+ if (!integer_zerop (iv->step))
+ fprintf (file, "[");
+
+ print_generic_expr (dump_file, iv->base, TDF_SLIM);
+
+ if (!integer_zerop (iv->step))
+ {
+ fprintf (file, ", + , ");
+ print_generic_expr (dump_file, iv->step, TDF_SLIM);
+ fprintf (file, "]%s", iv->no_overflow ? "(no_overflow)" : "");
+ }
+}
+
+/* Determine the number of iterations according to condition (for staying
+ inside loop) which compares two induction variables using comparison
+ operator CODE. The induction variable on left side of the comparison
+ is IV0, the right-hand side is IV1. Both induction variables must have
+ type TYPE, which must be an integer or pointer type. The steps of the
+ ivs must be constants (or NULL_TREE, which is interpreted as constant zero).
+
+ LOOP is the loop whose number of iterations we are determining.
+
+ ONLY_EXIT is true if we are sure this is the only way the loop could be
+ exited (including possibly non-returning function calls, exceptions, etc.)
+ -- in this case we can use the information whether the control induction
+ variables can overflow or not in a more efficient way.
+
+ The results (number of iterations and assumptions as described in
+ comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
+ Returns false if it fails to determine number of iterations, true if it
+ was determined (possibly with some assumptions). */
+
+static bool
+number_of_iterations_cond (struct loop *loop,
+ tree type, affine_iv *iv0, enum tree_code code,
+ affine_iv *iv1, struct tree_niter_desc *niter,
+ bool only_exit)
+{
+ bool never_infinite, ret;
+ bounds bnds;
+
+ /* The meaning of these assumptions is this:
+ if !assumptions
+ then the rest of information does not have to be valid
+ if may_be_zero then the loop does not roll, even if
+ niter != 0. */
+ niter->assumptions = boolean_true_node;
+ niter->may_be_zero = boolean_false_node;
+ niter->niter = NULL_TREE;
+ niter->max = double_int_zero;
+
+ niter->bound = NULL_TREE;
+ niter->cmp = ERROR_MARK;
+
+ /* Make < comparison from > ones, and for NE_EXPR comparisons, ensure that
+ the control variable is on lhs. */
+ if (code == GE_EXPR || code == GT_EXPR
+ || (code == NE_EXPR && integer_zerop (iv0->step)))
+ {
+ SWAP (iv0, iv1);
+ code = swap_tree_comparison (code);
+ }
+
+ if (!only_exit)
+ {
+ /* If this is not the only possible exit from the loop, the information
+ that the induction variables cannot overflow as derived from
+ signedness analysis cannot be relied upon. We use them e.g. in the
+ following way: given loop for (i = 0; i <= n; i++), if i is
+ signed, it cannot overflow, thus this loop is equivalent to
+ for (i = 0; i < n + 1; i++); however, if n == MAX, but the loop
+ is exited in some other way before i overflows, this transformation
+ is incorrect (the new loop exits immediately). */
+ iv0->no_overflow = false;
+ iv1->no_overflow = false;
+ }
+
+ if (POINTER_TYPE_P (type))
+ {
+ /* Comparison of pointers is undefined unless both iv0 and iv1 point
+ to the same object. If they do, the control variable cannot wrap
+ (as wrap around the bounds of memory will never return a pointer
+ that would be guaranteed to point to the same object, even if we
+ avoid undefined behavior by casting to size_t and back). The
+ restrictions on pointer arithmetics and comparisons of pointers
+ ensure that using the no-overflow assumptions is correct in this
+ case even if ONLY_EXIT is false. */
+ iv0->no_overflow = true;
+ iv1->no_overflow = true;
+ }
+
+ /* If the control induction variable does not overflow, the loop obviously
+ cannot be infinite. */
+ if (!integer_zerop (iv0->step) && iv0->no_overflow)
+ never_infinite = true;
+ else if (!integer_zerop (iv1->step) && iv1->no_overflow)
+ never_infinite = true;
+ else
+ never_infinite = false;
+
+ /* We can handle the case when neither of the sides of the comparison is
+ invariant, provided that the test is NE_EXPR. This rarely occurs in
+ practice, but it is simple enough to manage. */
+ if (!integer_zerop (iv0->step) && !integer_zerop (iv1->step))
+ {
+ if (code != NE_EXPR)
+ return false;
+
+ iv0->step = fold_binary_to_constant (MINUS_EXPR, type,
+ iv0->step, iv1->step);
+ iv0->no_overflow = false;
+ iv1->step = build_int_cst (type, 0);
+ iv1->no_overflow = true;
+ }
+
+ /* If the result of the comparison is a constant, the loop is weird. More
+ precise handling would be possible, but the situation is not common enough
+ to waste time on it. */
+ if (integer_zerop (iv0->step) && integer_zerop (iv1->step))
+ return false;
+
+ /* Ignore loops of while (i-- < 10) type. */
+ if (code != NE_EXPR)
+ {
+ if (iv0->step && tree_int_cst_sign_bit (iv0->step))
return false;
- niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
- base0, base1);
- niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
+ if (!integer_zerop (iv1->step) && !tree_int_cst_sign_bit (iv1->step))
+ return false;
+ }
+
+ /* If the loop exits immediately, there is nothing to do. */
+ if (integer_zerop (fold_build2 (code, boolean_type_node, iv0->base, iv1->base)))
+ {
+ niter->niter = build_int_cst (unsigned_type_for (type), 0);
+ niter->max = double_int_zero;
+ return true;
+ }
+
+ /* OK, now we know we have a senseful loop. Handle several cases, depending
+ on what comparison operator is used. */
+ bound_difference (loop, iv1->base, iv0->base, &bnds);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file,
+ "Analyzing # of iterations of loop %d\n", loop->num);
+
+ fprintf (dump_file, " exit condition ");
+ dump_affine_iv (dump_file, iv0);
+ fprintf (dump_file, " %s ",
+ code == NE_EXPR ? "!="
+ : code == LT_EXPR ? "<"
+ : "<=");
+ dump_affine_iv (dump_file, iv1);
+ fprintf (dump_file, "\n");
+
+ fprintf (dump_file, " bounds on difference of bases: ");
+ mpz_out_str (dump_file, 10, bnds.below);
+ fprintf (dump_file, " ... ");
+ mpz_out_str (dump_file, 10, bnds.up);
+ fprintf (dump_file, "\n");
+ }
+
+ switch (code)
+ {
+ case NE_EXPR:
+ gcc_assert (integer_zerop (iv1->step));
+ ret = number_of_iterations_ne (type, iv0, iv1->base, niter,
+ never_infinite, &bnds);
+ break;
+
+ case LT_EXPR:
+ ret = number_of_iterations_lt (type, iv0, iv1, niter, never_infinite,
+ &bnds);
+ break;
+
+ case LE_EXPR:
+ ret = number_of_iterations_le (type, iv0, iv1, niter, never_infinite,
+ &bnds);
break;
default:
gcc_unreachable ();
}
- niter->niter = fold_convert (niter_type, niter->niter);
- niter->additional_info = boolean_true_node;
- return true;
+ mpz_clear (bnds.up);
+ mpz_clear (bnds.below);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ if (ret)
+ {
+ fprintf (dump_file, " result:\n");
+ if (!integer_nonzerop (niter->assumptions))
+ {
+ fprintf (dump_file, " under assumptions ");
+ print_generic_expr (dump_file, niter->assumptions, TDF_SLIM);
+ fprintf (dump_file, "\n");
+ }
+
+ if (!integer_zerop (niter->may_be_zero))
+ {
+ fprintf (dump_file, " zero if ");
+ print_generic_expr (dump_file, niter->may_be_zero, TDF_SLIM);
+ fprintf (dump_file, "\n");
+ }
+
+ fprintf (dump_file, " # of iterations ");
+ print_generic_expr (dump_file, niter->niter, TDF_SLIM);
+ fprintf (dump_file, ", bounded by ");
+ dump_double_int (dump_file, niter->max, true);
+ fprintf (dump_file, "\n");
+ }
+ else
+ fprintf (dump_file, " failed\n\n");
+ }
+ return ret;
}
/* Substitute NEW for OLD in EXPR and fold the result. */
static tree
-simplify_replace_tree (tree expr, tree old, tree new)
+simplify_replace_tree (tree expr, tree old, tree new_tree)
{
unsigned i, n;
tree ret = NULL_TREE, e, se;
if (expr == old
|| operand_equal_p (expr, old, 0))
- return unshare_expr (new);
+ return unshare_expr (new_tree);
if (!EXPR_P (expr))
return expr;
- n = TREE_CODE_LENGTH (TREE_CODE (expr));
+ n = TREE_OPERAND_LENGTH (expr);
for (i = 0; i < n; i++)
{
e = TREE_OPERAND (expr, i);
- se = simplify_replace_tree (e, old, new);
+ se = simplify_replace_tree (e, old, new_tree);
if (e == se)
continue;
return (ret ? fold (ret) : expr);
}
+/* Expand definitions of ssa names in EXPR as long as they are simple
+ enough, and return the new expression. */
+
+tree
+expand_simple_operations (tree expr)
+{
+ unsigned i, n;
+ tree ret = NULL_TREE, e, ee, e1;
+ enum tree_code code;
+ gimple stmt;
+
+ if (expr == NULL_TREE)
+ return expr;
+
+ if (is_gimple_min_invariant (expr))
+ return expr;
+
+ code = TREE_CODE (expr);
+ if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code)))
+ {
+ n = TREE_OPERAND_LENGTH (expr);
+ for (i = 0; i < n; i++)
+ {
+ e = TREE_OPERAND (expr, i);
+ ee = expand_simple_operations (e);
+ if (e == ee)
+ continue;
+
+ if (!ret)
+ ret = copy_node (expr);
+
+ TREE_OPERAND (ret, i) = ee;
+ }
+
+ if (!ret)
+ return expr;
+
+ fold_defer_overflow_warnings ();
+ ret = fold (ret);
+ fold_undefer_and_ignore_overflow_warnings ();
+ return ret;
+ }
+
+ if (TREE_CODE (expr) != SSA_NAME)
+ return expr;
+
+ stmt = SSA_NAME_DEF_STMT (expr);
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ {
+ basic_block src, dest;
+
+ if (gimple_phi_num_args (stmt) != 1)
+ return expr;
+ e = PHI_ARG_DEF (stmt, 0);
+
+ /* Avoid propagating through loop exit phi nodes, which
+ could break loop-closed SSA form restrictions. */
+ dest = gimple_bb (stmt);
+ src = single_pred (dest);
+ if (TREE_CODE (e) == SSA_NAME
+ && src->loop_father != dest->loop_father)
+ return expr;
+
+ return expand_simple_operations (e);
+ }
+ if (gimple_code (stmt) != GIMPLE_ASSIGN)
+ return expr;
+
+ e = gimple_assign_rhs1 (stmt);
+ code = gimple_assign_rhs_code (stmt);
+ if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
+ {
+ if (is_gimple_min_invariant (e))
+ return e;
+
+ if (code == SSA_NAME)
+ return expand_simple_operations (e);
+
+ return expr;
+ }
+
+ switch (code)
+ {
+ CASE_CONVERT:
+ /* Casts are simple. */
+ ee = expand_simple_operations (e);
+ return fold_build1 (code, TREE_TYPE (expr), ee);
+
+ case PLUS_EXPR:
+ case MINUS_EXPR:
+ case POINTER_PLUS_EXPR:
+ /* And increments and decrements by a constant are simple. */
+ e1 = gimple_assign_rhs2 (stmt);
+ if (!is_gimple_min_invariant (e1))
+ return expr;
+
+ ee = expand_simple_operations (e);
+ return fold_build2 (code, TREE_TYPE (expr), ee, e1);
+
+ default:
+ return expr;
+ }
+}
+
/* Tries to simplify EXPR using the condition COND. Returns the simplified
- expression (or EXPR unchanged, if no simplification was possible).*/
+ expression (or EXPR unchanged, if no simplification was possible). */
static tree
-tree_simplify_using_condition (tree cond, tree expr)
+tree_simplify_using_condition_1 (tree cond, tree expr)
{
bool changed;
- tree e, e0, e1, e2, notcond;
+ tree e, te, e0, e1, e2, notcond;
enum tree_code code = TREE_CODE (expr);
if (code == INTEGER_CST)
{
changed = false;
- e0 = tree_simplify_using_condition (cond, TREE_OPERAND (expr, 0));
+ e0 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 0));
if (TREE_OPERAND (expr, 0) != e0)
changed = true;
- e1 = tree_simplify_using_condition (cond, TREE_OPERAND (expr, 1));
+ e1 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 1));
if (TREE_OPERAND (expr, 1) != e1)
changed = true;
if (code == COND_EXPR)
{
- e2 = tree_simplify_using_condition (cond, TREE_OPERAND (expr, 2));
+ e2 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 2));
if (TREE_OPERAND (expr, 2) != e2)
changed = true;
}
/* We know that e0 == e1. Check whether we cannot simplify expr
using this fact. */
e = simplify_replace_tree (expr, e0, e1);
- if (zero_p (e) || nonzero_p (e))
+ if (integer_zerop (e) || integer_nonzerop (e))
return e;
e = simplify_replace_tree (expr, e1, e0);
- if (zero_p (e) || nonzero_p (e))
+ if (integer_zerop (e) || integer_nonzerop (e))
return e;
}
if (TREE_CODE (expr) == EQ_EXPR)
/* If e0 == e1 (EXPR) implies !COND, then EXPR cannot be true. */
e = simplify_replace_tree (cond, e0, e1);
- if (zero_p (e))
+ if (integer_zerop (e))
return e;
e = simplify_replace_tree (cond, e1, e0);
- if (zero_p (e))
+ if (integer_zerop (e))
return e;
}
if (TREE_CODE (expr) == NE_EXPR)
/* If e0 == e1 (!EXPR) implies !COND, then EXPR must be true. */
e = simplify_replace_tree (cond, e0, e1);
- if (zero_p (e))
+ if (integer_zerop (e))
return boolean_true_node;
e = simplify_replace_tree (cond, e1, e0);
- if (zero_p (e))
+ if (integer_zerop (e))
return boolean_true_node;
}
+ te = expand_simple_operations (expr);
+
/* Check whether COND ==> EXPR. */
notcond = invert_truthvalue (cond);
- e = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- notcond, expr);
- if (nonzero_p (e))
+ e = fold_binary (TRUTH_OR_EXPR, boolean_type_node, notcond, te);
+ if (e && integer_nonzerop (e))
return e;
/* Check whether COND ==> not EXPR. */
- e = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
- cond, expr);
- if (zero_p (e))
+ e = fold_binary (TRUTH_AND_EXPR, boolean_type_node, cond, te);
+ if (e && integer_zerop (e))
return e;
return expr;
}
+/* Tries to simplify EXPR using the condition COND. Returns the simplified
+ expression (or EXPR unchanged, if no simplification was possible).
+ Wrapper around tree_simplify_using_condition_1 that ensures that chains
+ of simple operations in definitions of ssa names in COND are expanded,
+ so that things like casts or incrementing the value of the bound before
+ the loop do not cause us to fail. */
+
+static tree
+tree_simplify_using_condition (tree cond, tree expr)
+{
+ cond = expand_simple_operations (cond);
+
+ return tree_simplify_using_condition_1 (cond, expr);
+}
+
/* Tries to simplify EXPR using the conditions on entry to LOOP.
- Record the conditions used for simplification to CONDS_USED.
Returns the simplified expression (or EXPR unchanged, if no
simplification was possible).*/
static tree
-simplify_using_initial_conditions (struct loop *loop, tree expr,
- tree *conds_used)
+simplify_using_initial_conditions (struct loop *loop, tree expr)
{
edge e;
basic_block bb;
- tree exp, cond;
+ gimple stmt;
+ tree cond;
+ int cnt = 0;
if (TREE_CODE (expr) == INTEGER_CST)
return expr;
+ /* Limit walking the dominators to avoid quadraticness in
+ the number of BBs times the number of loops in degenerate
+ cases. */
for (bb = loop->header;
- bb != ENTRY_BLOCK_PTR;
+ bb != ENTRY_BLOCK_PTR && cnt < MAX_DOMINATORS_TO_WALK;
bb = get_immediate_dominator (CDI_DOMINATORS, bb))
{
if (!single_pred_p (bb))
if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
continue;
- cond = COND_EXPR_COND (last_stmt (e->src));
+ stmt = last_stmt (e->src);
+ cond = fold_build2 (gimple_cond_code (stmt),
+ boolean_type_node,
+ gimple_cond_lhs (stmt),
+ gimple_cond_rhs (stmt));
if (e->flags & EDGE_FALSE_VALUE)
cond = invert_truthvalue (cond);
- exp = tree_simplify_using_condition (cond, expr);
-
- if (exp != expr)
- *conds_used = fold_build2 (TRUTH_AND_EXPR,
- boolean_type_node,
- *conds_used,
- cond);
-
- expr = exp;
+ expr = tree_simplify_using_condition (cond, expr);
+ ++cnt;
}
return expr;
return expr;
}
-/* Stores description of number of iterations of LOOP derived from
- EXIT (an exit edge of the LOOP) in NITER. Returns true if some
- useful information could be derived (and fields of NITER has
- meaning described in comments at struct tree_niter_desc
- declaration), false otherwise. */
+/* Returns true if EXIT is the only possible exit from LOOP. */
bool
-number_of_iterations_exit (struct loop *loop, edge exit,
- struct tree_niter_desc *niter)
+loop_only_exit_p (const struct loop *loop, const_edge exit)
{
- tree stmt, cond, type;
- tree op0, base0, step0;
- tree op1, base1, step1;
- enum tree_code code;
+ basic_block *body;
+ gimple_stmt_iterator bsi;
+ unsigned i;
+ gimple call;
- if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src))
+ if (exit != single_exit (loop))
return false;
- niter->assumptions = boolean_false_node;
+ body = get_loop_body (loop);
+ for (i = 0; i < loop->num_nodes; i++)
+ {
+ for (bsi = gsi_start_bb (body[i]); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ call = gsi_stmt (bsi);
+ if (gimple_code (call) != GIMPLE_CALL)
+ continue;
+
+ if (gimple_has_side_effects (call))
+ {
+ free (body);
+ return false;
+ }
+ }
+ }
+
+ free (body);
+ return true;
+}
+
+/* Stores description of number of iterations of LOOP derived from
+ EXIT (an exit edge of the LOOP) in NITER. Returns true if some
+ useful information could be derived (and fields of NITER has
+ meaning described in comments at struct tree_niter_desc
+ declaration), false otherwise. If WARN is true and
+ -Wunsafe-loop-optimizations was given, warn if the optimizer is going to use
+ potentially unsafe assumptions. */
+
+bool
+number_of_iterations_exit (struct loop *loop, edge exit,
+ struct tree_niter_desc *niter,
+ bool warn)
+{
+ gimple stmt;
+ tree type;
+ tree op0, op1;
+ enum tree_code code;
+ affine_iv iv0, iv1;
+
+ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src))
+ return false;
+
+ niter->assumptions = boolean_false_node;
stmt = last_stmt (exit->src);
- if (!stmt || TREE_CODE (stmt) != COND_EXPR)
+ if (!stmt || gimple_code (stmt) != GIMPLE_COND)
return false;
/* We want the condition for staying inside loop. */
- cond = COND_EXPR_COND (stmt);
+ code = gimple_cond_code (stmt);
if (exit->flags & EDGE_TRUE_VALUE)
- cond = invert_truthvalue (cond);
+ code = invert_tree_comparison (code, false);
- code = TREE_CODE (cond);
switch (code)
{
case GT_EXPR:
return false;
}
- op0 = TREE_OPERAND (cond, 0);
- op1 = TREE_OPERAND (cond, 1);
+ op0 = gimple_cond_lhs (stmt);
+ op1 = gimple_cond_rhs (stmt);
type = TREE_TYPE (op0);
if (TREE_CODE (type) != INTEGER_TYPE
&& !POINTER_TYPE_P (type))
return false;
- if (!simple_iv (loop, stmt, op0, &base0, &step0))
+ if (!simple_iv (loop, loop_containing_stmt (stmt), op0, &iv0, false))
return false;
- if (!simple_iv (loop, stmt, op1, &base1, &step1))
+ if (!simple_iv (loop, loop_containing_stmt (stmt), op1, &iv1, false))
return false;
- niter->niter = NULL_TREE;
+ /* We don't want to see undefined signed overflow warnings while
+ computing the number of iterations. */
+ fold_defer_overflow_warnings ();
- /* Handle common special cases first, so that we do not need to use
- generic (and slow) analysis very often. */
- if (!number_of_iterations_special (type, base0, step0, code, base1, step1,
- niter))
+ iv0.base = expand_simple_operations (iv0.base);
+ iv1.base = expand_simple_operations (iv1.base);
+ if (!number_of_iterations_cond (loop, type, &iv0, code, &iv1, niter,
+ loop_only_exit_p (loop, exit)))
{
-
- number_of_iterations_cond (type, base0, step0, code, base1, step1,
- niter);
-
- if (!niter->niter)
- return false;
+ fold_undefer_and_ignore_overflow_warnings ();
+ return false;
}
if (optimize >= 3)
niter->niter = simplify_using_outer_evolutions (loop, niter->niter);
}
- niter->additional_info = boolean_true_node;
niter->assumptions
= simplify_using_initial_conditions (loop,
- niter->assumptions,
- &niter->additional_info);
+ niter->assumptions);
niter->may_be_zero
= simplify_using_initial_conditions (loop,
- niter->may_be_zero,
- &niter->additional_info);
- return integer_onep (niter->assumptions);
+ niter->may_be_zero);
+
+ fold_undefer_and_ignore_overflow_warnings ();
+
+ if (integer_onep (niter->assumptions))
+ return true;
+
+ /* With -funsafe-loop-optimizations we assume that nothing bad can happen.
+ But if we can prove that there is overflow or some other source of weird
+ behavior, ignore the loop even with -funsafe-loop-optimizations. */
+ if (integer_zerop (niter->assumptions))
+ return false;
+
+ if (flag_unsafe_loop_optimizations)
+ niter->assumptions = boolean_true_node;
+
+ if (warn)
+ {
+ const char *wording;
+ location_t loc = gimple_location (stmt);
+
+ /* We can provide a more specific warning if one of the operator is
+ constant and the other advances by +1 or -1. */
+ if (!integer_zerop (iv1.step)
+ ? (integer_zerop (iv0.step)
+ && (integer_onep (iv1.step) || integer_all_onesp (iv1.step)))
+ : (integer_onep (iv0.step) || integer_all_onesp (iv0.step)))
+ wording =
+ flag_unsafe_loop_optimizations
+ ? N_("assuming that the loop is not infinite")
+ : N_("cannot optimize possibly infinite loops");
+ else
+ wording =
+ flag_unsafe_loop_optimizations
+ ? N_("assuming that the loop counter does not overflow")
+ : N_("cannot optimize loop, the loop counter may overflow");
+
+ if (LOCATION_LINE (loc) > 0)
+ warning (OPT_Wunsafe_loop_optimizations, "%H%s", &loc, gettext (wording));
+ else
+ warning (OPT_Wunsafe_loop_optimizations, "%s", gettext (wording));
+ }
+
+ return flag_unsafe_loop_optimizations;
}
/* Try to determine the number of iterations of LOOP. If we succeed,
tree
find_loop_niter (struct loop *loop, edge *exit)
{
- unsigned n_exits, i;
- edge *exits = get_loop_exit_edges (loop, &n_exits);
+ unsigned i;
+ VEC (edge, heap) *exits = get_loop_exit_edges (loop);
edge ex;
tree niter = NULL_TREE, aniter;
struct tree_niter_desc desc;
*exit = NULL;
- for (i = 0; i < n_exits; i++)
+ for (i = 0; VEC_iterate (edge, exits, i, ex); i++)
{
- ex = exits[i];
if (!just_once_each_iteration_p (loop, ex->src))
continue;
- if (!number_of_iterations_exit (loop, ex, &desc))
+ if (!number_of_iterations_exit (loop, ex, &desc, false))
continue;
- if (nonzero_p (desc.may_be_zero))
+ if (integer_nonzerop (desc.may_be_zero))
{
/* We exit in the first iteration through this exit.
We won't find anything better. */
- niter = build_int_cst_type (unsigned_type_node, 0);
+ niter = build_int_cst (unsigned_type_node, 0);
*exit = ex;
break;
}
- if (!zero_p (desc.may_be_zero))
+ if (!integer_zerop (desc.may_be_zero))
continue;
aniter = desc.niter;
continue;
}
}
- free (exits);
+ VEC_free (edge, heap, exits);
return niter ? niter : chrec_dont_know;
}
result by a chain of operations such that all but exactly one of their
operands are constants. */
-static tree
+static gimple
chain_of_csts_start (struct loop *loop, tree x)
{
- tree stmt = SSA_NAME_DEF_STMT (x);
- basic_block bb = bb_for_stmt (stmt);
- use_optype uses;
+ gimple stmt = SSA_NAME_DEF_STMT (x);
+ tree use;
+ basic_block bb = gimple_bb (stmt);
+ enum tree_code code;
if (!bb
|| !flow_bb_inside_loop_p (loop, bb))
- return NULL_TREE;
+ return NULL;
- if (TREE_CODE (stmt) == PHI_NODE)
+ if (gimple_code (stmt) == GIMPLE_PHI)
{
if (bb == loop->header)
return stmt;
- return NULL_TREE;
+ return NULL;
}
- if (TREE_CODE (stmt) != MODIFY_EXPR)
- return NULL_TREE;
-
- get_stmt_operands (stmt);
- if (NUM_VUSES (STMT_VUSE_OPS (stmt)) > 0)
- return NULL_TREE;
- if (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) > 0)
- return NULL_TREE;
- if (NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) > 0)
- return NULL_TREE;
- if (NUM_DEFS (STMT_DEF_OPS (stmt)) > 1)
- return NULL_TREE;
- uses = STMT_USE_OPS (stmt);
- if (NUM_USES (uses) != 1)
- return NULL_TREE;
-
- return chain_of_csts_start (loop, USE_OP (uses, 0));
+ if (gimple_code (stmt) != GIMPLE_ASSIGN)
+ return NULL;
+
+ code = gimple_assign_rhs_code (stmt);
+ if (gimple_references_memory_p (stmt)
+ /* Before alias information is computed, operand scanning marks
+ statements that write memory volatile. However, the statements
+ that only read memory are not marked, thus gimple_references_memory_p
+ returns false for them. */
+ || TREE_CODE_CLASS (code) == tcc_reference
+ || TREE_CODE_CLASS (code) == tcc_declaration
+ || SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_DEF) == NULL_DEF_OPERAND_P)
+ return NULL;
+
+ use = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
+ if (use == NULL_USE_OPERAND_P)
+ return NULL;
+
+ return chain_of_csts_start (loop, use);
}
/* Determines whether the expression X is derived from a result of a phi node
* the value of the phi node in the next iteration can be derived from the
value in the current iteration by a chain of operations with constants.
- If such phi node exists, it is returned. If X is a constant, X is returned
- unchanged. Otherwise NULL_TREE is returned. */
+ If such phi node exists, it is returned, otherwise NULL is returned. */
+
+static gimple
+get_base_for (struct loop *loop, tree x)
+{
+ gimple phi;
+ tree init, next;
+
+ if (is_gimple_min_invariant (x))
+ return NULL;
+
+ phi = chain_of_csts_start (loop, x);
+ if (!phi)
+ return NULL;
+
+ init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
+ next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
+
+ if (TREE_CODE (next) != SSA_NAME)
+ return NULL;
+
+ if (!is_gimple_min_invariant (init))
+ return NULL;
+
+ if (chain_of_csts_start (loop, next) != phi)
+ return NULL;
+
+ return phi;
+}
+
+/* Given an expression X, then
+
+ * if X is NULL_TREE, we return the constant BASE.
+ * otherwise X is a SSA name, whose value in the considered loop is derived
+ by a chain of operations with constant from a result of a phi node in
+ the header of the loop. Then we return value of X when the value of the
+ result of this phi node is given by the constant BASE. */
+
+static tree
+get_val_for (tree x, tree base)
+{
+ gimple stmt;
+
+ gcc_assert (is_gimple_min_invariant (base));
+
+ if (!x)
+ return base;
+
+ stmt = SSA_NAME_DEF_STMT (x);
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ return base;
+
+ gcc_assert (is_gimple_assign (stmt));
+
+ /* STMT must be either an assignment of a single SSA name or an
+ expression involving an SSA name and a constant. Try to fold that
+ expression using the value for the SSA name. */
+ if (gimple_assign_ssa_name_copy_p (stmt))
+ return get_val_for (gimple_assign_rhs1 (stmt), base);
+ else if (gimple_assign_rhs_class (stmt) == GIMPLE_UNARY_RHS
+ && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)
+ {
+ return fold_build1 (gimple_assign_rhs_code (stmt),
+ gimple_expr_type (stmt),
+ get_val_for (gimple_assign_rhs1 (stmt), base));
+ }
+ else if (gimple_assign_rhs_class (stmt) == GIMPLE_BINARY_RHS)
+ {
+ tree rhs1 = gimple_assign_rhs1 (stmt);
+ tree rhs2 = gimple_assign_rhs2 (stmt);
+ if (TREE_CODE (rhs1) == SSA_NAME)
+ rhs1 = get_val_for (rhs1, base);
+ else if (TREE_CODE (rhs2) == SSA_NAME)
+ rhs2 = get_val_for (rhs2, base);
+ else
+ gcc_unreachable ();
+ return fold_build2 (gimple_assign_rhs_code (stmt),
+ gimple_expr_type (stmt), rhs1, rhs2);
+ }
+ else
+ gcc_unreachable ();
+}
+
+
+/* Tries to count the number of iterations of LOOP till it exits by EXIT
+ by brute force -- i.e. by determining the value of the operands of the
+ condition at EXIT in first few iterations of the loop (assuming that
+ these values are constant) and determining the first one in that the
+ condition is not satisfied. Returns the constant giving the number
+ of the iterations of LOOP if successful, chrec_dont_know otherwise. */
+
+tree
+loop_niter_by_eval (struct loop *loop, edge exit)
+{
+ tree acnd;
+ tree op[2], val[2], next[2], aval[2];
+ gimple phi, cond;
+ unsigned i, j;
+ enum tree_code cmp;
+
+ cond = last_stmt (exit->src);
+ if (!cond || gimple_code (cond) != GIMPLE_COND)
+ return chrec_dont_know;
+
+ cmp = gimple_cond_code (cond);
+ if (exit->flags & EDGE_TRUE_VALUE)
+ cmp = invert_tree_comparison (cmp, false);
+
+ switch (cmp)
+ {
+ case EQ_EXPR:
+ case NE_EXPR:
+ case GT_EXPR:
+ case GE_EXPR:
+ case LT_EXPR:
+ case LE_EXPR:
+ op[0] = gimple_cond_lhs (cond);
+ op[1] = gimple_cond_rhs (cond);
+ break;
+
+ default:
+ return chrec_dont_know;
+ }
+
+ for (j = 0; j < 2; j++)
+ {
+ if (is_gimple_min_invariant (op[j]))
+ {
+ val[j] = op[j];
+ next[j] = NULL_TREE;
+ op[j] = NULL_TREE;
+ }
+ else
+ {
+ phi = get_base_for (loop, op[j]);
+ if (!phi)
+ return chrec_dont_know;
+ val[j] = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
+ next[j] = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
+ }
+ }
+
+ /* Don't issue signed overflow warnings. */
+ fold_defer_overflow_warnings ();
+
+ for (i = 0; i < MAX_ITERATIONS_TO_TRACK; i++)
+ {
+ for (j = 0; j < 2; j++)
+ aval[j] = get_val_for (op[j], val[j]);
+
+ acnd = fold_binary (cmp, boolean_type_node, aval[0], aval[1]);
+ if (acnd && integer_zerop (acnd))
+ {
+ fold_undefer_and_ignore_overflow_warnings ();
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ "Proved that loop %d iterates %d times using brute force.\n",
+ loop->num, i);
+ return build_int_cst (unsigned_type_node, i);
+ }
+
+ for (j = 0; j < 2; j++)
+ {
+ val[j] = get_val_for (next[j], val[j]);
+ if (!is_gimple_min_invariant (val[j]))
+ {
+ fold_undefer_and_ignore_overflow_warnings ();
+ return chrec_dont_know;
+ }
+ }
+ }
+
+ fold_undefer_and_ignore_overflow_warnings ();
+
+ return chrec_dont_know;
+}
+
+/* Finds the exit of the LOOP by that the loop exits after a constant
+ number of iterations and stores the exit edge to *EXIT. The constant
+ giving the number of iterations of LOOP is returned. The number of
+ iterations is determined using loop_niter_by_eval (i.e. by brute force
+ evaluation). If we are unable to find the exit for that loop_niter_by_eval
+ determines the number of iterations, chrec_dont_know is returned. */
+
+tree
+find_loop_niter_by_eval (struct loop *loop, edge *exit)
+{
+ unsigned i;
+ VEC (edge, heap) *exits = get_loop_exit_edges (loop);
+ edge ex;
+ tree niter = NULL_TREE, aniter;
+
+ *exit = NULL;
+ for (i = 0; VEC_iterate (edge, exits, i, ex); i++)
+ {
+ if (!just_once_each_iteration_p (loop, ex->src))
+ continue;
+
+ aniter = loop_niter_by_eval (loop, ex);
+ if (chrec_contains_undetermined (aniter))
+ continue;
+
+ if (niter
+ && !tree_int_cst_lt (aniter, niter))
+ continue;
+
+ niter = aniter;
+ *exit = ex;
+ }
+ VEC_free (edge, heap, exits);
+
+ return niter ? niter : chrec_dont_know;
+}
+
+/*
+
+ Analysis of upper bounds on number of iterations of a loop.
+
+*/
+
+static double_int derive_constant_upper_bound_ops (tree, tree,
+ enum tree_code, tree);
+
+/* Returns a constant upper bound on the value of the right-hand side of
+ an assignment statement STMT. */
+
+static double_int
+derive_constant_upper_bound_assign (gimple stmt)
+{
+ enum tree_code code = gimple_assign_rhs_code (stmt);
+ tree op0 = gimple_assign_rhs1 (stmt);
+ tree op1 = gimple_assign_rhs2 (stmt);
+
+ return derive_constant_upper_bound_ops (TREE_TYPE (gimple_assign_lhs (stmt)),
+ op0, code, op1);
+}
+
+/* Returns a constant upper bound on the value of expression VAL. VAL
+ is considered to be unsigned. If its type is signed, its value must
+ be nonnegative. */
+
+static double_int
+derive_constant_upper_bound (tree val)
+{
+ enum tree_code code;
+ tree op0, op1;
+
+ extract_ops_from_tree (val, &code, &op0, &op1);
+ return derive_constant_upper_bound_ops (TREE_TYPE (val), op0, code, op1);
+}
+
+/* Returns a constant upper bound on the value of expression OP0 CODE OP1,
+ whose type is TYPE. The expression is considered to be unsigned. If
+ its type is signed, its value must be nonnegative. */
+
+static double_int
+derive_constant_upper_bound_ops (tree type, tree op0,
+ enum tree_code code, tree op1)
+{
+ tree subtype, maxt;
+ double_int bnd, max, mmax, cst;
+ gimple stmt;
+
+ if (INTEGRAL_TYPE_P (type))
+ maxt = TYPE_MAX_VALUE (type);
+ else
+ maxt = upper_bound_in_type (type, type);
+
+ max = tree_to_double_int (maxt);
+
+ switch (code)
+ {
+ case INTEGER_CST:
+ return tree_to_double_int (op0);
+
+ CASE_CONVERT:
+ subtype = TREE_TYPE (op0);
+ if (!TYPE_UNSIGNED (subtype)
+ /* If TYPE is also signed, the fact that VAL is nonnegative implies
+ that OP0 is nonnegative. */
+ && TYPE_UNSIGNED (type)
+ && !tree_expr_nonnegative_p (op0))
+ {
+ /* If we cannot prove that the casted expression is nonnegative,
+ we cannot establish more useful upper bound than the precision
+ of the type gives us. */
+ return max;
+ }
+
+ /* We now know that op0 is an nonnegative value. Try deriving an upper
+ bound for it. */
+ bnd = derive_constant_upper_bound (op0);
+
+ /* If the bound does not fit in TYPE, max. value of TYPE could be
+ attained. */
+ if (double_int_ucmp (max, bnd) < 0)
+ return max;
+
+ return bnd;
+
+ case PLUS_EXPR:
+ case POINTER_PLUS_EXPR:
+ case MINUS_EXPR:
+ if (TREE_CODE (op1) != INTEGER_CST
+ || !tree_expr_nonnegative_p (op0))
+ return max;
+
+ /* Canonicalize to OP0 - CST. Consider CST to be signed, in order to
+ choose the most logical way how to treat this constant regardless
+ of the signedness of the type. */
+ cst = tree_to_double_int (op1);
+ cst = double_int_sext (cst, TYPE_PRECISION (type));
+ if (code != MINUS_EXPR)
+ cst = double_int_neg (cst);
+
+ bnd = derive_constant_upper_bound (op0);
+
+ if (double_int_negative_p (cst))
+ {
+ cst = double_int_neg (cst);
+ /* Avoid CST == 0x80000... */
+ if (double_int_negative_p (cst))
+ return max;;
+
+ /* OP0 + CST. We need to check that
+ BND <= MAX (type) - CST. */
+
+ mmax = double_int_add (max, double_int_neg (cst));
+ if (double_int_ucmp (bnd, mmax) > 0)
+ return max;
+
+ return double_int_add (bnd, cst);
+ }
+ else
+ {
+ /* OP0 - CST, where CST >= 0.
+
+ If TYPE is signed, we have already verified that OP0 >= 0, and we
+ know that the result is nonnegative. This implies that
+ VAL <= BND - CST.
+
+ If TYPE is unsigned, we must additionally know that OP0 >= CST,
+ otherwise the operation underflows.
+ */
+
+ /* This should only happen if the type is unsigned; however, for
+ buggy programs that use overflowing signed arithmetics even with
+ -fno-wrapv, this condition may also be true for signed values. */
+ if (double_int_ucmp (bnd, cst) < 0)
+ return max;
+
+ if (TYPE_UNSIGNED (type))
+ {
+ tree tem = fold_binary (GE_EXPR, boolean_type_node, op0,
+ double_int_to_tree (type, cst));
+ if (!tem || integer_nonzerop (tem))
+ return max;
+ }
+
+ bnd = double_int_add (bnd, double_int_neg (cst));
+ }
+
+ return bnd;
+
+ case FLOOR_DIV_EXPR:
+ case EXACT_DIV_EXPR:
+ if (TREE_CODE (op1) != INTEGER_CST
+ || tree_int_cst_sign_bit (op1))
+ return max;
+
+ bnd = derive_constant_upper_bound (op0);
+ return double_int_udiv (bnd, tree_to_double_int (op1), FLOOR_DIV_EXPR);
+
+ case BIT_AND_EXPR:
+ if (TREE_CODE (op1) != INTEGER_CST
+ || tree_int_cst_sign_bit (op1))
+ return max;
+ return tree_to_double_int (op1);
+
+ case SSA_NAME:
+ stmt = SSA_NAME_DEF_STMT (op0);
+ if (gimple_code (stmt) != GIMPLE_ASSIGN
+ || gimple_assign_lhs (stmt) != op0)
+ return max;
+ return derive_constant_upper_bound_assign (stmt);
+
+ default:
+ return max;
+ }
+}
+
+/* Records that every statement in LOOP is executed I_BOUND times.
+ REALISTIC is true if I_BOUND is expected to be close to the real number
+ of iterations. UPPER is true if we are sure the loop iterates at most
+ I_BOUND times. */
+
+static void
+record_niter_bound (struct loop *loop, double_int i_bound, bool realistic,
+ bool upper)
+{
+ /* Update the bounds only when there is no previous estimation, or when the current
+ estimation is smaller. */
+ if (upper
+ && (!loop->any_upper_bound
+ || double_int_ucmp (i_bound, loop->nb_iterations_upper_bound) < 0))
+ {
+ loop->any_upper_bound = true;
+ loop->nb_iterations_upper_bound = i_bound;
+ }
+ if (realistic
+ && (!loop->any_estimate
+ || double_int_ucmp (i_bound, loop->nb_iterations_estimate) < 0))
+ {
+ loop->any_estimate = true;
+ loop->nb_iterations_estimate = i_bound;
+ }
+}
+
+/* Records that AT_STMT is executed at most BOUND + 1 times in LOOP. IS_EXIT
+ is true if the loop is exited immediately after STMT, and this exit
+ is taken at last when the STMT is executed BOUND + 1 times.
+ REALISTIC is true if BOUND is expected to be close to the real number
+ of iterations. UPPER is true if we are sure the loop iterates at most
+ BOUND times. I_BOUND is an unsigned double_int upper estimate on BOUND. */
+
+static void
+record_estimate (struct loop *loop, tree bound, double_int i_bound,
+ gimple at_stmt, bool is_exit, bool realistic, bool upper)
+{
+ double_int delta;
+ edge exit;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Statement %s", is_exit ? "(exit)" : "");
+ print_gimple_stmt (dump_file, at_stmt, 0, TDF_SLIM);
+ fprintf (dump_file, " is %sexecuted at most ",
+ upper ? "" : "probably ");
+ print_generic_expr (dump_file, bound, TDF_SLIM);
+ fprintf (dump_file, " (bounded by ");
+ dump_double_int (dump_file, i_bound, true);
+ fprintf (dump_file, ") + 1 times in loop %d.\n", loop->num);
+ }
+
+ /* If the I_BOUND is just an estimate of BOUND, it rarely is close to the
+ real number of iterations. */
+ if (TREE_CODE (bound) != INTEGER_CST)
+ realistic = false;
+ if (!upper && !realistic)
+ return;
+
+ /* If we have a guaranteed upper bound, record it in the appropriate
+ list. */
+ if (upper)
+ {
+ struct nb_iter_bound *elt = GGC_NEW (struct nb_iter_bound);
+
+ elt->bound = i_bound;
+ elt->stmt = at_stmt;
+ elt->is_exit = is_exit;
+ elt->next = loop->bounds;
+ loop->bounds = elt;
+ }
+
+ /* Update the number of iteration estimates according to the bound.
+ If at_stmt is an exit, then every statement in the loop is
+ executed at most BOUND + 1 times. If it is not an exit, then
+ some of the statements before it could be executed BOUND + 2
+ times, if an exit of LOOP is before stmt. */
+ exit = single_exit (loop);
+ if (is_exit
+ || (exit != NULL
+ && dominated_by_p (CDI_DOMINATORS,
+ exit->src, gimple_bb (at_stmt))))
+ delta = double_int_one;
+ else
+ delta = double_int_two;
+ i_bound = double_int_add (i_bound, delta);
+
+ /* If an overflow occurred, ignore the result. */
+ if (double_int_ucmp (i_bound, delta) < 0)
+ return;
+
+ record_niter_bound (loop, i_bound, realistic, upper);
+}
+
+/* Record the estimate on number of iterations of LOOP based on the fact that
+ the induction variable BASE + STEP * i evaluated in STMT does not wrap and
+ its values belong to the range <LOW, HIGH>. REALISTIC is true if the
+ estimated number of iterations is expected to be close to the real one.
+ UPPER is true if we are sure the induction variable does not wrap. */
+
+static void
+record_nonwrapping_iv (struct loop *loop, tree base, tree step, gimple stmt,
+ tree low, tree high, bool realistic, bool upper)
+{
+ tree niter_bound, extreme, delta;
+ tree type = TREE_TYPE (base), unsigned_type;
+ double_int max;
+
+ if (TREE_CODE (step) != INTEGER_CST || integer_zerop (step))
+ return;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Induction variable (");
+ print_generic_expr (dump_file, TREE_TYPE (base), TDF_SLIM);
+ fprintf (dump_file, ") ");
+ print_generic_expr (dump_file, base, TDF_SLIM);
+ fprintf (dump_file, " + ");
+ print_generic_expr (dump_file, step, TDF_SLIM);
+ fprintf (dump_file, " * iteration does not wrap in statement ");
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
+ fprintf (dump_file, " in loop %d.\n", loop->num);
+ }
+
+ unsigned_type = unsigned_type_for (type);
+ base = fold_convert (unsigned_type, base);
+ step = fold_convert (unsigned_type, step);
+
+ if (tree_int_cst_sign_bit (step))
+ {
+ extreme = fold_convert (unsigned_type, low);
+ if (TREE_CODE (base) != INTEGER_CST)
+ base = fold_convert (unsigned_type, high);
+ delta = fold_build2 (MINUS_EXPR, unsigned_type, base, extreme);
+ step = fold_build1 (NEGATE_EXPR, unsigned_type, step);
+ }
+ else
+ {
+ extreme = fold_convert (unsigned_type, high);
+ if (TREE_CODE (base) != INTEGER_CST)
+ base = fold_convert (unsigned_type, low);
+ delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, base);
+ }
+
+ /* STMT is executed at most NITER_BOUND + 1 times, since otherwise the value
+ would get out of the range. */
+ niter_bound = fold_build2 (FLOOR_DIV_EXPR, unsigned_type, delta, step);
+ max = derive_constant_upper_bound (niter_bound);
+ record_estimate (loop, niter_bound, max, stmt, false, realistic, upper);
+}
+
+/* Returns true if REF is a reference to an array at the end of a dynamically
+ allocated structure. If this is the case, the array may be allocated larger
+ than its upper bound implies. */
+
+static bool
+array_at_struct_end_p (tree ref)
+{
+ tree base = get_base_address (ref);
+ tree parent, field;
+
+ /* Unless the reference is through a pointer, the size of the array matches
+ its declaration. */
+ if (!base || !INDIRECT_REF_P (base))
+ return false;
+
+ for (;handled_component_p (ref); ref = parent)
+ {
+ parent = TREE_OPERAND (ref, 0);
-static tree
-get_base_for (struct loop *loop, tree x)
-{
- tree phi, init, next;
+ if (TREE_CODE (ref) == COMPONENT_REF)
+ {
+ /* All fields of a union are at its end. */
+ if (TREE_CODE (TREE_TYPE (parent)) == UNION_TYPE)
+ continue;
- if (is_gimple_min_invariant (x))
- return x;
+ /* Unless the field is at the end of the struct, we are done. */
+ field = TREE_OPERAND (ref, 1);
+ if (TREE_CHAIN (field))
+ return false;
+ }
- phi = chain_of_csts_start (loop, x);
- if (!phi)
- return NULL_TREE;
+ /* The other options are ARRAY_REF, ARRAY_RANGE_REF, VIEW_CONVERT_EXPR.
+ In all these cases, we might be accessing the last element, and
+ although in practice this will probably never happen, it is legal for
+ the indices of this last element to exceed the bounds of the array.
+ Therefore, continue checking. */
+ }
- init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
- next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
+ gcc_assert (INDIRECT_REF_P (ref));
+ return true;
+}
- if (TREE_CODE (next) != SSA_NAME)
- return NULL_TREE;
+/* Determine information about number of iterations a LOOP from the index
+ IDX of a data reference accessed in STMT. RELIABLE is true if STMT is
+ guaranteed to be executed in every iteration of LOOP. Callback for
+ for_each_index. */
- if (!is_gimple_min_invariant (init))
- return NULL_TREE;
+struct ilb_data
+{
+ struct loop *loop;
+ gimple stmt;
+ bool reliable;
+};
- if (chain_of_csts_start (loop, next) != phi)
- return NULL_TREE;
+static bool
+idx_infer_loop_bounds (tree base, tree *idx, void *dta)
+{
+ struct ilb_data *data = (struct ilb_data *) dta;
+ tree ev, init, step;
+ tree low, high, type, next;
+ bool sign, upper = data->reliable, at_end = false;
+ struct loop *loop = data->loop;
- return phi;
-}
+ if (TREE_CODE (base) != ARRAY_REF)
+ return true;
-/* Given an expression X, then
-
- * if BASE is NULL_TREE, X must be a constant and we return X.
- * otherwise X is a SSA name, whose value in the considered loop is derived
- by a chain of operations with constant from a result of a phi node in
- the header of the loop. Then we return value of X when the value of the
- result of this phi node is given by the constant BASE. */
+ /* For arrays at the end of the structure, we are not guaranteed that they
+ do not really extend over their declared size. However, for arrays of
+ size greater than one, this is unlikely to be intended. */
+ if (array_at_struct_end_p (base))
+ {
+ at_end = true;
+ upper = false;
+ }
-static tree
-get_val_for (tree x, tree base)
-{
- tree stmt, nx, val;
- use_optype uses;
- use_operand_p op;
+ ev = instantiate_parameters (loop, analyze_scalar_evolution (loop, *idx));
+ init = initial_condition (ev);
+ step = evolution_part_in_loop_num (ev, loop->num);
- if (!x)
- return base;
+ if (!init
+ || !step
+ || TREE_CODE (step) != INTEGER_CST
+ || integer_zerop (step)
+ || tree_contains_chrecs (init, NULL)
+ || chrec_contains_symbols_defined_in_loop (init, loop->num))
+ return true;
- stmt = SSA_NAME_DEF_STMT (x);
- if (TREE_CODE (stmt) == PHI_NODE)
- return base;
+ low = array_ref_low_bound (base);
+ high = array_ref_up_bound (base);
+
+ /* The case of nonconstant bounds could be handled, but it would be
+ complicated. */
+ if (TREE_CODE (low) != INTEGER_CST
+ || !high
+ || TREE_CODE (high) != INTEGER_CST)
+ return true;
+ sign = tree_int_cst_sign_bit (step);
+ type = TREE_TYPE (step);
+
+ /* The array of length 1 at the end of a structure most likely extends
+ beyond its bounds. */
+ if (at_end
+ && operand_equal_p (low, high, 0))
+ return true;
- uses = STMT_USE_OPS (stmt);
- op = USE_OP_PTR (uses, 0);
+ /* In case the relevant bound of the array does not fit in type, or
+ it does, but bound + step (in type) still belongs into the range of the
+ array, the index may wrap and still stay within the range of the array
+ (consider e.g. if the array is indexed by the full range of
+ unsigned char).
- nx = USE_FROM_PTR (op);
- val = get_val_for (nx, base);
- SET_USE (op, val);
- val = fold (TREE_OPERAND (stmt, 1));
- SET_USE (op, nx);
+ To make things simpler, we require both bounds to fit into type, although
+ there are cases where this would not be strictly necessary. */
+ if (!int_fits_type_p (high, type)
+ || !int_fits_type_p (low, type))
+ return true;
+ low = fold_convert (type, low);
+ high = fold_convert (type, high);
+
+ if (sign)
+ next = fold_binary (PLUS_EXPR, type, low, step);
+ else
+ next = fold_binary (PLUS_EXPR, type, high, step);
+
+ if (tree_int_cst_compare (low, next) <= 0
+ && tree_int_cst_compare (next, high) <= 0)
+ return true;
- return val;
+ record_nonwrapping_iv (loop, init, step, data->stmt, low, high, true, upper);
+ return true;
}
-/* Tries to count the number of iterations of LOOP till it exits by EXIT
- by brute force -- i.e. by determining the value of the operands of the
- condition at EXIT in first few iterations of the loop (assuming that
- these values are constant) and determining the first one in that the
- condition is not satisfied. Returns the constant giving the number
- of the iterations of LOOP if successful, chrec_dont_know otherwise. */
+/* Determine information about number of iterations a LOOP from the bounds
+ of arrays in the data reference REF accessed in STMT. RELIABLE is true if
+ STMT is guaranteed to be executed in every iteration of LOOP.*/
-tree
-loop_niter_by_eval (struct loop *loop, edge exit)
+static void
+infer_loop_bounds_from_ref (struct loop *loop, gimple stmt, tree ref,
+ bool reliable)
{
- tree cond, cnd, acnd;
- tree op[2], val[2], next[2], aval[2], phi[2];
- unsigned i, j;
- enum tree_code cmp;
+ struct ilb_data data;
- cond = last_stmt (exit->src);
- if (!cond || TREE_CODE (cond) != COND_EXPR)
- return chrec_dont_know;
+ data.loop = loop;
+ data.stmt = stmt;
+ data.reliable = reliable;
+ for_each_index (&ref, idx_infer_loop_bounds, &data);
+}
- cnd = COND_EXPR_COND (cond);
- if (exit->flags & EDGE_TRUE_VALUE)
- cnd = invert_truthvalue (cnd);
+/* Determine information about number of iterations of a LOOP from the way
+ arrays are used in STMT. RELIABLE is true if STMT is guaranteed to be
+ executed in every iteration of LOOP. */
- cmp = TREE_CODE (cnd);
- switch (cmp)
+static void
+infer_loop_bounds_from_array (struct loop *loop, gimple stmt, bool reliable)
+{
+ if (is_gimple_assign (stmt))
{
- case EQ_EXPR:
- case NE_EXPR:
- case GT_EXPR:
- case GE_EXPR:
- case LT_EXPR:
- case LE_EXPR:
- for (j = 0; j < 2; j++)
- op[j] = TREE_OPERAND (cnd, j);
- break;
+ tree op0 = gimple_assign_lhs (stmt);
+ tree op1 = gimple_assign_rhs1 (stmt);
- default:
- return chrec_dont_know;
- }
+ /* For each memory access, analyze its access function
+ and record a bound on the loop iteration domain. */
+ if (REFERENCE_CLASS_P (op0))
+ infer_loop_bounds_from_ref (loop, stmt, op0, reliable);
- for (j = 0; j < 2; j++)
- {
- phi[j] = get_base_for (loop, op[j]);
- if (!phi[j])
- return chrec_dont_know;
+ if (REFERENCE_CLASS_P (op1))
+ infer_loop_bounds_from_ref (loop, stmt, op1, reliable);
}
-
- for (j = 0; j < 2; j++)
+ else if (is_gimple_call (stmt))
{
- if (TREE_CODE (phi[j]) == PHI_NODE)
- {
- val[j] = PHI_ARG_DEF_FROM_EDGE (phi[j], loop_preheader_edge (loop));
- next[j] = PHI_ARG_DEF_FROM_EDGE (phi[j], loop_latch_edge (loop));
- }
- else
- {
- val[j] = phi[j];
- next[j] = NULL_TREE;
- op[j] = NULL_TREE;
- }
- }
+ tree arg, lhs;
+ unsigned i, n = gimple_call_num_args (stmt);
- for (i = 0; i < MAX_ITERATIONS_TO_TRACK; i++)
- {
- for (j = 0; j < 2; j++)
- aval[j] = get_val_for (op[j], val[j]);
+ lhs = gimple_call_lhs (stmt);
+ if (lhs && REFERENCE_CLASS_P (lhs))
+ infer_loop_bounds_from_ref (loop, stmt, lhs, reliable);
- acnd = fold_build2 (cmp, boolean_type_node, aval[0], aval[1]);
- if (zero_p (acnd))
+ for (i = 0; i < n; i++)
{
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file,
- "Proved that loop %d iterates %d times using brute force.\n",
- loop->num, i);
- return build_int_cst (unsigned_type_node, i);
+ arg = gimple_call_arg (stmt, i);
+ if (REFERENCE_CLASS_P (arg))
+ infer_loop_bounds_from_ref (loop, stmt, arg, reliable);
}
-
- for (j = 0; j < 2; j++)
- val[j] = get_val_for (next[j], val[j]);
}
-
- return chrec_dont_know;
}
-/* Finds the exit of the LOOP by that the loop exits after a constant
- number of iterations and stores the exit edge to *EXIT. The constant
- giving the number of iterations of LOOP is returned. The number of
- iterations is determined using loop_niter_by_eval (i.e. by brute force
- evaluation). If we are unable to find the exit for that loop_niter_by_eval
- determines the number of iterations, chrec_dont_know is returned. */
+/* Determine information about number of iterations of a LOOP from the fact
+ that signed arithmetics in STMT does not overflow. */
-tree
-find_loop_niter_by_eval (struct loop *loop, edge *exit)
+static void
+infer_loop_bounds_from_signedness (struct loop *loop, gimple stmt)
{
- unsigned n_exits, i;
- edge *exits = get_loop_exit_edges (loop, &n_exits);
- edge ex;
- tree niter = NULL_TREE, aniter;
+ tree def, base, step, scev, type, low, high;
- *exit = NULL;
- for (i = 0; i < n_exits; i++)
- {
- ex = exits[i];
- if (!just_once_each_iteration_p (loop, ex->src))
- continue;
+ if (gimple_code (stmt) != GIMPLE_ASSIGN)
+ return;
- aniter = loop_niter_by_eval (loop, ex);
- if (chrec_contains_undetermined (aniter))
- continue;
+ def = gimple_assign_lhs (stmt);
- if (niter
- && !tree_int_cst_lt (aniter, niter))
- continue;
+ if (TREE_CODE (def) != SSA_NAME)
+ return;
- niter = aniter;
- *exit = ex;
- }
- free (exits);
+ type = TREE_TYPE (def);
+ if (!INTEGRAL_TYPE_P (type)
+ || !TYPE_OVERFLOW_UNDEFINED (type))
+ return;
- return niter ? niter : chrec_dont_know;
+ scev = instantiate_parameters (loop, analyze_scalar_evolution (loop, def));
+ if (chrec_contains_undetermined (scev))
+ return;
+
+ base = initial_condition_in_loop_num (scev, loop->num);
+ step = evolution_part_in_loop_num (scev, loop->num);
+
+ if (!base || !step
+ || TREE_CODE (step) != INTEGER_CST
+ || tree_contains_chrecs (base, NULL)
+ || chrec_contains_symbols_defined_in_loop (base, loop->num))
+ return;
+
+ low = lower_bound_in_type (type, type);
+ high = upper_bound_in_type (type, type);
+
+ record_nonwrapping_iv (loop, base, step, stmt, low, high, false, true);
}
-/*
+/* The following analyzers are extracting informations on the bounds
+ of LOOP from the following undefined behaviors:
- Analysis of upper bounds on number of iterations of a loop.
+ - data references should not access elements over the statically
+ allocated size,
+ - signed variables should not overflow when flag_wrapv is not set.
*/
-/* Records that AT_STMT is executed at most BOUND times in LOOP. The
- additional condition ADDITIONAL is recorded with the bound. */
-
-void
-record_estimate (struct loop *loop, tree bound, tree additional, tree at_stmt)
+static void
+infer_loop_bounds_from_undefined (struct loop *loop)
{
- struct nb_iter_bound *elt = xmalloc (sizeof (struct nb_iter_bound));
+ unsigned i;
+ basic_block *bbs;
+ gimple_stmt_iterator bsi;
+ basic_block bb;
+ bool reliable;
+
+ bbs = get_loop_body (loop);
- if (dump_file && (dump_flags & TDF_DETAILS))
+ for (i = 0; i < loop->num_nodes; i++)
{
- fprintf (dump_file, "Statements after ");
- print_generic_expr (dump_file, at_stmt, TDF_SLIM);
- fprintf (dump_file, " are executed at most ");
- print_generic_expr (dump_file, bound, TDF_SLIM);
- fprintf (dump_file, " times in loop %d.\n", loop->num);
+ bb = bbs[i];
+
+ /* If BB is not executed in each iteration of the loop, we cannot
+ use the operations in it to infer reliable upper bound on the
+ # of iterations of the loop. However, we can use it as a guess. */
+ reliable = dominated_by_p (CDI_DOMINATORS, loop->latch, bb);
+
+ for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+
+ infer_loop_bounds_from_array (loop, stmt, reliable);
+
+ if (reliable)
+ infer_loop_bounds_from_signedness (loop, stmt);
+ }
+
}
- elt->bound = bound;
- elt->at_stmt = at_stmt;
- elt->additional = additional;
- elt->next = loop->bounds;
- loop->bounds = elt;
+ free (bbs);
+}
+
+/* Converts VAL to double_int. */
+
+static double_int
+gcov_type_to_double_int (gcov_type val)
+{
+ double_int ret;
+
+ ret.low = (unsigned HOST_WIDE_INT) val;
+ /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
+ the size of type. */
+ val >>= HOST_BITS_PER_WIDE_INT - 1;
+ val >>= 1;
+ ret.high = (unsigned HOST_WIDE_INT) val;
+
+ return ret;
}
/* Records estimates on numbers of iterations of LOOP. */
-static void
+void
estimate_numbers_of_iterations_loop (struct loop *loop)
{
- edge *exits;
+ VEC (edge, heap) *exits;
tree niter, type;
- unsigned i, n_exits;
+ unsigned i;
struct tree_niter_desc niter_desc;
+ edge ex;
+ double_int bound;
- exits = get_loop_exit_edges (loop, &n_exits);
- for (i = 0; i < n_exits; i++)
+ /* Give up if we already have tried to compute an estimation. */
+ if (loop->estimate_state != EST_NOT_COMPUTED)
+ return;
+ loop->estimate_state = EST_AVAILABLE;
+ loop->any_upper_bound = false;
+ loop->any_estimate = false;
+
+ exits = get_loop_exit_edges (loop);
+ for (i = 0; VEC_iterate (edge, exits, i, ex); i++)
{
- if (!number_of_iterations_exit (loop, exits[i], &niter_desc))
+ if (!number_of_iterations_exit (loop, ex, &niter_desc, false))
continue;
niter = niter_desc.niter;
type = TREE_TYPE (niter);
- if (!zero_p (niter_desc.may_be_zero)
- && !nonzero_p (niter_desc.may_be_zero))
+ if (TREE_CODE (niter_desc.may_be_zero) != INTEGER_CST)
niter = build3 (COND_EXPR, type, niter_desc.may_be_zero,
- build_int_cst_type (type, 0),
+ build_int_cst (type, 0),
niter);
- record_estimate (loop, niter,
- niter_desc.additional_info,
- last_stmt (exits[i]->src));
+ record_estimate (loop, niter, niter_desc.max,
+ last_stmt (ex->src),
+ true, true, true);
}
- free (exits);
+ VEC_free (edge, heap, exits);
- /* Analyzes the bounds of arrays accessed in the loop. */
- if (loop->estimated_nb_iterations == NULL_TREE)
+ infer_loop_bounds_from_undefined (loop);
+
+ /* If we have a measured profile, use it to estimate the number of
+ iterations. */
+ if (loop->header->count != 0)
{
- varray_type datarefs;
- VARRAY_GENERIC_PTR_INIT (datarefs, 3, "datarefs");
- find_data_references_in_loop (loop, &datarefs);
- free_data_refs (datarefs);
+ gcov_type nit = expected_loop_iterations_unbounded (loop) + 1;
+ bound = gcov_type_to_double_int (nit);
+ record_niter_bound (loop, bound, true, false);
}
+
+ /* If an upper bound is smaller than the realistic estimate of the
+ number of iterations, use the upper bound instead. */
+ if (loop->any_upper_bound
+ && loop->any_estimate
+ && double_int_ucmp (loop->nb_iterations_upper_bound,
+ loop->nb_iterations_estimate) < 0)
+ loop->nb_iterations_estimate = loop->nb_iterations_upper_bound;
}
-/* Records estimates on numbers of iterations of LOOPS. */
+/* Records estimates on numbers of iterations of loops. */
void
-estimate_numbers_of_iterations (struct loops *loops)
+estimate_numbers_of_iterations (void)
{
- unsigned i;
+ loop_iterator li;
struct loop *loop;
- for (i = 1; i < loops->num; i++)
+ /* We don't want to issue signed overflow warnings while getting
+ loop iteration estimates. */
+ fold_defer_overflow_warnings ();
+
+ FOR_EACH_LOOP (li, loop, 0)
{
- loop = loops->parray[i];
- if (loop)
- estimate_numbers_of_iterations_loop (loop);
+ estimate_numbers_of_iterations_loop (loop);
}
-}
-
-/* If A > B, returns -1. If A == B, returns 0. If A < B, returns 1.
- If neither of these relations can be proved, returns 2. */
-static int
-compare_trees (tree a, tree b)
-{
- tree typea = TREE_TYPE (a), typeb = TREE_TYPE (b);
- tree type;
-
- if (TYPE_PRECISION (typea) > TYPE_PRECISION (typeb))
- type = typea;
- else
- type = typeb;
-
- a = fold_convert (type, a);
- b = fold_convert (type, b);
-
- if (nonzero_p (fold_build2 (EQ_EXPR, boolean_type_node, a, b)))
- return 0;
- if (nonzero_p (fold_build2 (LT_EXPR, boolean_type_node, a, b)))
- return 1;
- if (nonzero_p (fold_build2 (GT_EXPR, boolean_type_node, a, b)))
- return -1;
-
- return 2;
+ fold_undefer_and_ignore_overflow_warnings ();
}
/* Returns true if statement S1 dominates statement S2. */
-static bool
-stmt_dominates_stmt_p (tree s1, tree s2)
+bool
+stmt_dominates_stmt_p (gimple s1, gimple s2)
{
- basic_block bb1 = bb_for_stmt (s1), bb2 = bb_for_stmt (s2);
+ basic_block bb1 = gimple_bb (s1), bb2 = gimple_bb (s2);
if (!bb1
|| s1 == s2)
if (bb1 == bb2)
{
- block_stmt_iterator bsi;
+ gimple_stmt_iterator bsi;
+
+ if (gimple_code (s2) == GIMPLE_PHI)
+ return false;
+
+ if (gimple_code (s1) == GIMPLE_PHI)
+ return true;
- for (bsi = bsi_start (bb1); bsi_stmt (bsi) != s2; bsi_next (&bsi))
- if (bsi_stmt (bsi) == s1)
+ for (bsi = gsi_start_bb (bb1); gsi_stmt (bsi) != s2; gsi_next (&bsi))
+ if (gsi_stmt (bsi) == s1)
return true;
return false;
return dominated_by_p (CDI_DOMINATORS, bb2, bb1);
}
-/* Checks whether it is correct to count the induction variable BASE + STEP * I
- at AT_STMT in wider TYPE, using the fact that statement OF is executed at
- most BOUND times in the loop. If it is possible, return the value of step
- of the induction variable in the TYPE, otherwise return NULL_TREE.
-
- ADDITIONAL is the additional condition recorded for operands of the bound.
- This is useful in the following case, created by loop header copying:
-
- i = 0;
- if (n > 0)
- do
- {
- something;
- } while (++i < n)
+/* Returns true when we can prove that the number of executions of
+ STMT in the loop is at most NITER, according to the bound on
+ the number of executions of the statement NITER_BOUND->stmt recorded in
+ NITER_BOUND. If STMT is NULL, we must prove this bound for all
+ statements in the loop. */
- If the n > 0 condition is taken into account, the number of iterations of the
- loop can be expressed as n - 1. If the type of n is signed, the ADDITIONAL
- assumption "n > 0" says us that the value of the number of iterations is at
- most MAX_TYPE - 1 (without this assumption, it might overflow). */
-
-static tree
-can_count_iv_in_wider_type_bound (tree type, tree base, tree step,
- tree at_stmt,
- tree bound,
- tree additional,
- tree of)
+static bool
+n_of_executions_at_most (gimple stmt,
+ struct nb_iter_bound *niter_bound,
+ tree niter)
{
- tree inner_type = TREE_TYPE (base), b, bplusstep, new_step, new_step_abs;
- tree valid_niter, extreme, unsigned_type, delta, bound_type;
- tree cond;
-
- b = fold_convert (type, base);
- bplusstep = fold_convert (type,
- fold_build2 (PLUS_EXPR, inner_type, base, step));
- new_step = fold_build2 (MINUS_EXPR, type, bplusstep, b);
- if (TREE_CODE (new_step) != INTEGER_CST)
- return NULL_TREE;
-
- switch (compare_trees (bplusstep, b))
- {
- case -1:
- extreme = upper_bound_in_type (type, inner_type);
- delta = fold_build2 (MINUS_EXPR, type, extreme, b);
- new_step_abs = new_step;
- break;
-
- case 1:
- extreme = lower_bound_in_type (type, inner_type);
- new_step_abs = fold_build1 (NEGATE_EXPR, type, new_step);
- delta = fold_build2 (MINUS_EXPR, type, b, extreme);
- break;
+ double_int bound = niter_bound->bound;
+ tree nit_type = TREE_TYPE (niter), e;
+ enum tree_code cmp;
- case 0:
- return new_step;
+ gcc_assert (TYPE_UNSIGNED (nit_type));
- default:
- return NULL_TREE;
- }
+ /* If the bound does not even fit into NIT_TYPE, it cannot tell us that
+ the number of iterations is small. */
+ if (!double_int_fits_to_tree_p (nit_type, bound))
+ return false;
- unsigned_type = unsigned_type_for (type);
- delta = fold_convert (unsigned_type, delta);
- new_step_abs = fold_convert (unsigned_type, new_step_abs);
- valid_niter = fold_build2 (FLOOR_DIV_EXPR, unsigned_type,
- delta, new_step_abs);
-
- bound_type = TREE_TYPE (bound);
- if (TYPE_PRECISION (type) > TYPE_PRECISION (bound_type))
- bound = fold_convert (unsigned_type, bound);
- else
- valid_niter = fold_convert (bound_type, valid_niter);
-
- if (at_stmt && stmt_dominates_stmt_p (of, at_stmt))
+ /* We know that NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
+ times. This means that:
+
+ -- if NITER_BOUND->is_exit is true, then everything before
+ NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
+ times, and everything after it at most NITER_BOUND->bound times.
+
+ -- If NITER_BOUND->is_exit is false, then if we can prove that when STMT
+ is executed, then NITER_BOUND->stmt is executed as well in the same
+ iteration (we conclude that if both statements belong to the same
+ basic block, or if STMT is after NITER_BOUND->stmt), then STMT
+ is executed at most NITER_BOUND->bound + 1 times. Otherwise STMT is
+ executed at most NITER_BOUND->bound + 2 times. */
+
+ if (niter_bound->is_exit)
{
- /* After the statement OF we know that anything is executed at most
- BOUND times. */
- cond = fold_build2 (GE_EXPR, boolean_type_node, valid_niter, bound);
+ if (stmt
+ && stmt != niter_bound->stmt
+ && stmt_dominates_stmt_p (niter_bound->stmt, stmt))
+ cmp = GE_EXPR;
+ else
+ cmp = GT_EXPR;
}
else
{
- /* Before the statement OF we know that anything is executed at most
- BOUND + 1 times. */
- cond = fold_build2 (GT_EXPR, boolean_type_node, valid_niter, bound);
+ if (!stmt
+ || (gimple_bb (stmt) != gimple_bb (niter_bound->stmt)
+ && !stmt_dominates_stmt_p (niter_bound->stmt, stmt)))
+ {
+ bound = double_int_add (bound, double_int_one);
+ if (double_int_zero_p (bound)
+ || !double_int_fits_to_tree_p (nit_type, bound))
+ return false;
+ }
+ cmp = GT_EXPR;
}
- if (nonzero_p (cond))
- return new_step;
+ e = fold_binary (cmp, boolean_type_node,
+ niter, double_int_to_tree (nit_type, bound));
+ return e && integer_nonzerop (e);
+}
+
+/* Returns true if the arithmetics in TYPE can be assumed not to wrap. */
+
+bool
+nowrap_type_p (tree type)
+{
+ if (INTEGRAL_TYPE_P (type)
+ && TYPE_OVERFLOW_UNDEFINED (type))
+ return true;
- /* Try taking additional conditions into account. */
- cond = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- invert_truthvalue (additional),
- cond);
- if (nonzero_p (cond))
- return new_step;
+ if (POINTER_TYPE_P (type))
+ return true;
- return NULL_TREE;
+ return false;
}
-/* Checks whether it is correct to count the induction variable BASE + STEP * I
- at AT_STMT in wider TYPE, using the bounds on numbers of iterations of a
- LOOP. If it is possible, return the value of step of the induction variable
- in the TYPE, otherwise return NULL_TREE. */
+/* Return false only when the induction variable BASE + STEP * I is
+ known to not overflow: i.e. when the number of iterations is small
+ enough with respect to the step and initial condition in order to
+ keep the evolution confined in TYPEs bounds. Return true when the
+ iv is known to overflow or when the property is not computable.
+
+ USE_OVERFLOW_SEMANTICS is true if this function should assume that
+ the rules for overflow of the given language apply (e.g., that signed
+ arithmetics in C does not overflow). */
-tree
-can_count_iv_in_wider_type (struct loop *loop, tree type, tree base, tree step,
- tree at_stmt)
+bool
+scev_probably_wraps_p (tree base, tree step,
+ gimple at_stmt, struct loop *loop,
+ bool use_overflow_semantics)
{
struct nb_iter_bound *bound;
- tree new_step;
+ tree delta, step_abs;
+ tree unsigned_type, valid_niter;
+ tree type = TREE_TYPE (step);
+
+ /* FIXME: We really need something like
+ http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html.
+
+ We used to test for the following situation that frequently appears
+ during address arithmetics:
+
+ D.1621_13 = (long unsigned intD.4) D.1620_12;
+ D.1622_14 = D.1621_13 * 8;
+ D.1623_15 = (doubleD.29 *) D.1622_14;
+
+ And derived that the sequence corresponding to D_14
+ can be proved to not wrap because it is used for computing a
+ memory access; however, this is not really the case -- for example,
+ if D_12 = (unsigned char) [254,+,1], then D_14 has values
+ 2032, 2040, 0, 8, ..., but the code is still legal. */
+
+ if (chrec_contains_undetermined (base)
+ || chrec_contains_undetermined (step))
+ return true;
- for (bound = loop->bounds; bound; bound = bound->next)
+ if (integer_zerop (step))
+ return false;
+
+ /* If we can use the fact that signed and pointer arithmetics does not
+ wrap, we are done. */
+ if (use_overflow_semantics && nowrap_type_p (TREE_TYPE (base)))
+ return false;
+
+ /* To be able to use estimates on number of iterations of the loop,
+ we must have an upper bound on the absolute value of the step. */
+ if (TREE_CODE (step) != INTEGER_CST)
+ return true;
+
+ /* Don't issue signed overflow warnings. */
+ fold_defer_overflow_warnings ();
+
+ /* Otherwise, compute the number of iterations before we reach the
+ bound of the type, and verify that the loop is exited before this
+ occurs. */
+ unsigned_type = unsigned_type_for (type);
+ base = fold_convert (unsigned_type, base);
+
+ if (tree_int_cst_sign_bit (step))
+ {
+ tree extreme = fold_convert (unsigned_type,
+ lower_bound_in_type (type, type));
+ delta = fold_build2 (MINUS_EXPR, unsigned_type, base, extreme);
+ step_abs = fold_build1 (NEGATE_EXPR, unsigned_type,
+ fold_convert (unsigned_type, step));
+ }
+ else
{
- new_step = can_count_iv_in_wider_type_bound (type, base, step,
- at_stmt,
- bound->bound,
- bound->additional,
- bound->at_stmt);
+ tree extreme = fold_convert (unsigned_type,
+ upper_bound_in_type (type, type));
+ delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, base);
+ step_abs = fold_convert (unsigned_type, step);
+ }
+
+ valid_niter = fold_build2 (FLOOR_DIV_EXPR, unsigned_type, delta, step_abs);
- if (new_step)
- return new_step;
+ estimate_numbers_of_iterations_loop (loop);
+ for (bound = loop->bounds; bound; bound = bound->next)
+ {
+ if (n_of_executions_at_most (at_stmt, bound, valid_niter))
+ {
+ fold_undefer_and_ignore_overflow_warnings ();
+ return false;
+ }
}
- return NULL_TREE;
+ fold_undefer_and_ignore_overflow_warnings ();
+
+ /* At this point we still don't have a proof that the iv does not
+ overflow: give up. */
+ return true;
}
/* Frees the information on upper bounds on numbers of iterations of LOOP. */
-static void
+void
free_numbers_of_iterations_estimates_loop (struct loop *loop)
{
struct nb_iter_bound *bound, *next;
-
+
+ loop->nb_iterations = NULL;
+ loop->estimate_state = EST_NOT_COMPUTED;
for (bound = loop->bounds; bound; bound = next)
{
next = bound->next;
- free (bound);
+ ggc_free (bound);
}
loop->bounds = NULL;
}
-/* Frees the information on upper bounds on numbers of iterations of LOOPS. */
+/* Frees the information on upper bounds on numbers of iterations of loops. */
void
-free_numbers_of_iterations_estimates (struct loops *loops)
+free_numbers_of_iterations_estimates (void)
{
- unsigned i;
+ loop_iterator li;
struct loop *loop;
- for (i = 1; i < loops->num; i++)
+ FOR_EACH_LOOP (li, loop, 0)
{
- loop = loops->parray[i];
- if (loop)
- free_numbers_of_iterations_estimates_loop (loop);
+ free_numbers_of_iterations_estimates_loop (loop);
}
}
+
+/* Substitute value VAL for ssa name NAME inside expressions held
+ at LOOP. */
+
+void
+substitute_in_loop_info (struct loop *loop, tree name, tree val)
+{
+ loop->nb_iterations = simplify_replace_tree (loop->nb_iterations, name, val);
+}
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