/* Functions to determine/estimate number of iterations of a loop.
- Copyright (C) 2004 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005 Free Software Foundation, Inc.
This file is part of GCC.
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. */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
#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"
#define SWAP(X, Y) do { void *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
-/* Just to shorten the ugly names. */
-#define EXEC_BINARY nondestructive_fold_binary_to_constant
-#define EXEC_UNARY nondestructive_fold_unary_to_constant
/*
return (TREE_INT_CST_LOW (arg) != 0 || TREE_INT_CST_HIGH (arg) != 0);
}
-/* Returns number of zeros at the end of binary representation of X.
-
- ??? Use ffs if available? */
-
-static tree
-num_ending_zeros (tree x)
-{
- unsigned HOST_WIDE_INT fr, nfr;
- unsigned num, abits;
- tree type = TREE_TYPE (x);
-
- if (TREE_INT_CST_LOW (x) == 0)
- {
- num = HOST_BITS_PER_WIDE_INT;
- fr = TREE_INT_CST_HIGH (x);
- }
- else
- {
- num = 0;
- fr = TREE_INT_CST_LOW (x);
- }
-
- for (abits = HOST_BITS_PER_WIDE_INT / 2; abits; abits /= 2)
- {
- nfr = fr >> abits;
- if (nfr << abits == fr)
- {
- num += abits;
- fr = nfr;
- }
- }
-
- if (num > TYPE_PRECISION (type))
- num = TYPE_PRECISION (type);
-
- return build_int_cst_type (type, num);
-}
-
/* Returns inverse of X modulo 2^s, where MASK = 2^s-1. */
static tree
rslt = build_int_cst_type (type, 1);
for (; ctr; ctr--)
{
- rslt = EXEC_BINARY (MULT_EXPR, type, rslt, x);
- x = EXEC_BINARY (MULT_EXPR, type, x, x);
+ rslt = int_const_binop (MULT_EXPR, rslt, x, 0);
+ x = int_const_binop (MULT_EXPR, x, x, 0);
}
- rslt = EXEC_BINARY (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. */
+/* 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). */
-void
-number_of_iterations_cond (tree type, tree base0, tree step0,
- enum tree_code code, tree base1, tree step1,
- struct tree_niter_desc *niter)
+static bool
+number_of_iterations_ne (tree type, affine_iv *iv, tree final,
+ struct tree_niter_desc *niter, bool never_infinite)
{
- 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;
+ tree niter_type = unsigned_type_for (type);
+ tree s, c, d, bits, assumption, tmp, bound;
- /* 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)
+ 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 (tree_int_cst_sign_bit (iv->step))
{
- SWAP (base0, base1);
- SWAP (step0, step1);
- code = swap_tree_comparison (code);
+ 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));
}
-
- /* 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))
+ else
{
- if (code != NE_EXPR)
- return;
+ 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));
+ }
- step0 = EXEC_BINARY (MINUS_EXPR, type, step0, step1);
- step1 = NULL_TREE;
+ /* First the trivial cases -- when the step is 1. */
+ if (integer_onep (s))
+ {
+ niter->niter = c;
+ return true;
}
- /* 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;
+ /* 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)));
- /* Ignore loops of while (i-- < 10) type. */
- if (code != NE_EXPR)
- {
- if (step0 && !tree_expr_nonnegative_p (step0))
- return;
+ 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, s, bits);
- if (!zero_p (step1) && tree_expr_nonnegative_p (step1))
- return;
+ 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 (!nonzero_p (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 (POINTER_TYPE_P (type))
+/* 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. */
+
+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)
+{
+ tree niter_type = TREE_TYPE (step);
+ tree mod = fold_build2 (FLOOR_MOD_EXPR, niter_type, *delta, step);
+ tree tmod;
+ tree assumption = boolean_true_node, bound, noloop;
+
+ if (TREE_CODE (mod) != INTEGER_CST)
+ return false;
+ if (nonzero_p (mod))
+ mod = fold_build2 (MINUS_EXPR, niter_type, step, mod);
+ tmod = fold_convert (type, mod);
+
+ if (nonzero_p (iv0->step))
{
- /* We assume pointer arithmetic never overflows. */
- mmin = mmax = NULL_TREE;
+ /* 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 (!iv1->no_overflow && !zero_p (mod))
+ {
+ bound = fold_build2 (MINUS_EXPR, type,
+ TYPE_MAX_VALUE (type), tmod);
+ assumption = fold_build2 (LE_EXPR, boolean_type_node,
+ iv1->base, bound);
+ if (zero_p (assumption))
+ return false;
+ }
+ noloop = fold_build2 (GT_EXPR, boolean_type_node,
+ iv0->base,
+ fold_build2 (PLUS_EXPR, type,
+ iv1->base, tmod));
}
else
{
- mmin = TYPE_MIN_VALUE (type);
- mmax = TYPE_MAX_VALUE (type);
+ /* 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 (!iv0->no_overflow && !zero_p (mod))
+ {
+ bound = fold_build2 (PLUS_EXPR, type,
+ TYPE_MIN_VALUE (type), tmod);
+ assumption = fold_build2 (GE_EXPR, boolean_type_node,
+ iv0->base, bound);
+ if (zero_p (assumption))
+ return false;
+ }
+ noloop = fold_build2 (GT_EXPR, boolean_type_node,
+ fold_build2 (MINUS_EXPR, type,
+ iv0->base, tmod),
+ iv1->base);
}
- /* Some more condition normalization. We must record some assumptions
- due to overflows. */
+ if (!nonzero_p (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions,
+ assumption);
+ if (!zero_p (noloop))
+ niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
+ niter->may_be_zero,
+ noloop);
+ *delta = fold_build2 (PLUS_EXPR, niter_type, *delta, mod);
+ return true;
+}
+
+/* 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
+assert_no_overflow_lt (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter, tree step)
+{
+ tree bound, d, assumption, diff;
+ tree niter_type = TREE_TYPE (step);
- if (code == LT_EXPR)
+ if (nonzero_p (iv0->step))
{
- /* 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))
+ /* for (i = iv0->base; i < iv1->base; i += iv0->step) */
+ if (iv0->no_overflow)
+ return true;
+
+ /* 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 (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)));
+ 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
+ diff = fold_build2 (MINUS_EXPR, niter_type, step,
+ build_int_cst_type (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 (TREE_CODE (iv1->base) == INTEGER_CST)
{
- 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)));
+ 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);
}
- noloop_assumptions = assumption;
- code = LE_EXPR;
-
- /* It will be useful to be able to tell the difference once more in
- <= -> != reduction. */
- was_sharp = true;
+ else
+ diff = fold_build2 (MINUS_EXPR, niter_type, step,
+ build_int_cst_type (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);
}
- /* 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;
- }
+ if (zero_p (assumption))
+ return false;
+ if (!nonzero_p (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+
+ iv0->no_overflow = true;
+ iv1->no_overflow = true;
+ return true;
+}
- /* 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)
+/* Add an assumption to NITER that a loop whose ending condition
+ is IV0 < IV1 rolls. TYPE is the type of the control iv. */
+
+static void
+assert_loop_rolls_lt (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter)
+{
+ tree assumption = boolean_true_node, bound, diff;
+ tree mbz, mbzl, mbzr;
+
+ if (nonzero_p (iv0->step))
{
- if (zero_p (step0))
- step = EXEC_UNARY (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;
+ diff = fold_build2 (MINUS_EXPR, type,
+ iv0->step, build_int_cst_type (type, 1));
- if (TREE_CODE (delta) == INTEGER_CST)
+ /* 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))
{
- tmp = EXEC_BINARY (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 = EXEC_BINARY (PLUS_EXPR, type, mmin, step);
- bound = EXEC_BINARY (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 = EXEC_BINARY (MINUS_EXPR, type, mmax, step);
- bound = EXEC_BINARY (PLUS_EXPR, type, bound, delta);
- may_xform = fold (build2 (LE_EXPR, boolean_type_node,
- base1, bound));
- }
- }
+ bound = fold_build2 (PLUS_EXPR, type,
+ TYPE_MIN_VALUE (type), diff);
+ assumption = fold_build2 (GE_EXPR, boolean_type_node,
+ iv0->base, bound);
}
- if (!zero_p (may_xform))
+ /* And then we can compute iv0->base - diff, and compare it with
+ iv1->base. */
+ mbzl = fold_build2 (MINUS_EXPR, type, iv0->base, diff);
+ mbzr = iv1->base;
+ }
+ else
+ {
+ diff = fold_build2 (PLUS_EXPR, type,
+ iv1->step, build_int_cst_type (type, 1));
+
+ if (!POINTER_TYPE_P (type))
{
- /* 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;
+ bound = fold_build2 (PLUS_EXPR, type,
+ TYPE_MAX_VALUE (type), diff);
+ assumption = fold_build2 (LE_EXPR, boolean_type_node,
+ iv1->base, bound);
+ }
- 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));
- }
+ mbzl = iv0->base;
+ mbzr = fold_build2 (MINUS_EXPR, type, iv1->base, diff);
+ }
- 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;
- }
+ mbz = fold_build2 (GT_EXPR, boolean_type_node, mbzl, mbzr);
+
+ if (!nonzero_p (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+ if (!zero_p (mbz))
+ 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. */
+
+static bool
+number_of_iterations_lt (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter,
+ bool never_infinite ATTRIBUTE_UNUSED)
+{
+ tree niter_type = unsigned_type_for (type);
+ tree delta, step, s;
+
+ if (nonzero_p (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;
}
- /* Count the number of iterations. */
- niter_type = unsigned_type_for (type);
- signed_niter_type = signed_type_for (type);
+ delta = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, iv1->base),
+ fold_convert (niter_type, iv0->base));
- if (code == NE_EXPR)
+ /* First handle the special case that the step is +-1. */
+ if ((iv0->step && integer_onep (iv0->step)
+ && zero_p (iv1->step))
+ || (iv1->step && integer_all_onesp (iv1->step)
+ && zero_p (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 = EXEC_UNARY (NEGATE_EXPR, type, step1);
- step1 = NULL_TREE;
- if (!tree_expr_nonnegative_p (fold_convert (signed_niter_type, step0)))
- {
- step0 = EXEC_UNARY (NEGATE_EXPR, type, step0);
- base1 = fold (build1 (NEGATE_EXPR, type, base1));
- }
+ /* for (i = iv0->base; i < iv1->base; i++)
- 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 = EXEC_BINARY (LSHIFT_EXPR, niter_type,
- build_int_cst_type (niter_type, 1), bits);
- s = EXEC_BINARY (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));
+ 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. */
+ niter->may_be_zero = fold_build2 (LT_EXPR, boolean_type_node,
+ iv1->base, iv0->base);
+ niter->niter = delta;
+ return true;
}
+
+ if (nonzero_p (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))
{
- 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). */
- {
- if (mmax)
- {
- bound = EXEC_BINARY (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));
- }
+ affine_iv zps;
- 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);
- }
- 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 = EXEC_BINARY (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;
+ zps.base = build_int_cst_type (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);
}
- niter->assumptions = assumptions;
- niter->may_be_zero = noloop_assumptions;
- return;
+ /* Make sure that the control iv does not overflow. */
+ if (!assert_no_overflow_lt (type, iv0, iv1, niter, step))
+ return false;
-zero_iter:
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_true_node;
- niter->niter = build_int_cst_type (type, 0);
- return;
+ /* 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);
+
+ s = fold_build2 (MINUS_EXPR, niter_type,
+ step, build_int_cst_type (niter_type, 1));
+ delta = fold_build2 (PLUS_EXPR, niter_type, delta, s);
+ niter->niter = fold_build2 (FLOOR_DIV_EXPR, niter_type, delta, step);
+ return true;
}
-/* Tries to simplify EXPR using the evolutions of the loop invariants
- in the superloops of LOOP. Returns the simplified expression
- (or EXPR unchanged, if no simplification was possible). */
+/* 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). */
-static tree
-simplify_using_outer_evolutions (struct loop *loop, tree expr)
+static bool
+number_of_iterations_le (tree type, affine_iv *iv0, affine_iv *iv1,
+ struct tree_niter_desc *niter, bool never_infinite)
{
- enum tree_code code = TREE_CODE (expr);
- bool changed;
- tree e, e0, e1, e2;
+ tree assumption;
- if (is_gimple_min_invariant (expr))
- return expr;
+ /* 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 (code == TRUTH_OR_EXPR
- || code == TRUTH_AND_EXPR
- || code == COND_EXPR)
+ if (!never_infinite)
{
- changed = false;
+ if (nonzero_p (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 (zero_p (assumption))
+ return false;
+ if (!nonzero_p (assumption))
+ niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
+ niter->assumptions, assumption);
+ }
- e0 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 0));
- if (TREE_OPERAND (expr, 0) != e0)
- changed = true;
+ if (nonzero_p (iv0->step))
+ iv1->base = fold_build2 (PLUS_EXPR, type,
+ iv1->base, build_int_cst_type (type, 1));
+ else
+ iv0->base = fold_build2 (MINUS_EXPR, type,
+ iv0->base, build_int_cst_type (type, 1));
+ return number_of_iterations_lt (type, iv0, iv1, niter, never_infinite);
+}
- e1 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 1));
- if (TREE_OPERAND (expr, 1) != e1)
- changed = true;
+/* 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).
+
+ 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). */
- if (code == COND_EXPR)
- {
- e2 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 2));
- if (TREE_OPERAND (expr, 2) != e2)
- changed = true;
- }
- else
- e2 = NULL_TREE;
+static bool
+number_of_iterations_cond (tree type, affine_iv *iv0, enum tree_code code,
+ affine_iv *iv1, struct tree_niter_desc *niter,
+ bool only_exit)
+{
+ bool never_infinite;
- if (changed)
- {
- if (code == COND_EXPR)
- expr = build3 (code, boolean_type_node, e0, e1, e2);
- else
- expr = build2 (code, boolean_type_node, e0, e1);
- expr = fold (expr);
- }
+ /* 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->additional_info = boolean_true_node;
- return expr;
+ 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 && zero_p (iv0->step)))
+ {
+ SWAP (iv0, iv1);
+ code = swap_tree_comparison (code);
}
- e = instantiate_parameters (loop, expr);
- if (is_gimple_min_invariant (e))
- return e;
+ 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;
+ }
- return expr;
+ 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 (!zero_p (iv0->step) && iv0->no_overflow)
+ never_infinite = true;
+ else if (!zero_p (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 (!zero_p (iv0->step) && !zero_p (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 = NULL_TREE;
+ 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 (zero_p (iv0->step) && zero_p (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;
+
+ if (!zero_p (iv1->step) && !tree_int_cst_sign_bit (iv1->step))
+ return false;
+ }
+
+ /* If the loop exits immediately, there is nothing to do. */
+ if (zero_p (fold_build2 (code, boolean_type_node, iv0->base, iv1->base)))
+ {
+ niter->niter = build_int_cst_type (unsigned_type_for (type), 0);
+ return true;
+ }
+
+ /* OK, now we know we have a senseful loop. Handle several cases, depending
+ on what comparison operator is used. */
+ switch (code)
+ {
+ case NE_EXPR:
+ gcc_assert (zero_p (iv1->step));
+ return number_of_iterations_ne (type, iv0, iv1->base, niter, never_infinite);
+ case LT_EXPR:
+ return number_of_iterations_lt (type, iv0, iv1, niter, never_infinite);
+ case LE_EXPR:
+ return number_of_iterations_le (type, iv0, iv1, niter, never_infinite);
+ default:
+ gcc_unreachable ();
+ }
}
/* Substitute NEW for OLD in EXPR and fold the result. */
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, stmt;
+ enum tree_code code;
+
+ 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_CODE_LENGTH (code);
+ 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;
+ }
+
+ return (ret ? fold (ret) : expr);
+ }
+
+ if (TREE_CODE (expr) != SSA_NAME)
+ return expr;
+
+ stmt = SSA_NAME_DEF_STMT (expr);
+ if (TREE_CODE (stmt) != MODIFY_EXPR)
+ return expr;
+
+ e = TREE_OPERAND (stmt, 1);
+ if (/* Casts are simple. */
+ TREE_CODE (e) != NOP_EXPR
+ && TREE_CODE (e) != CONVERT_EXPR
+ /* Copies are simple. */
+ && TREE_CODE (e) != SSA_NAME
+ /* Assignments of invariants are simple. */
+ && !is_gimple_min_invariant (e)
+ /* And increments and decrements by a constant are simple. */
+ && !((TREE_CODE (e) == PLUS_EXPR
+ || TREE_CODE (e) == MINUS_EXPR)
+ && is_gimple_min_invariant (TREE_OPERAND (e, 1))))
+ return expr;
+
+ return expand_simple_operations (e);
+}
+
/* 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;
}
if (changed)
{
if (code == COND_EXPR)
- expr = build3 (code, boolean_type_node, e0, e1, e2);
+ expr = fold_build3 (code, boolean_type_node, e0, e1, e2);
else
- expr = build2 (code, boolean_type_node, e0, e1);
- expr = fold (expr);
+ expr = fold_build2 (code, boolean_type_node, e0, e1);
}
return expr;
return boolean_true_node;
}
- /* Check whether COND ==> EXPR. */
- notcond = invert_truthvalue (cond);
- e = fold (build2 (TRUTH_OR_EXPR, boolean_type_node,
- notcond, expr));
- if (nonzero_p (e))
- return e;
-
- /* Check whether COND ==> not EXPR. */
- e = fold (build2 (TRUTH_AND_EXPR, boolean_type_node,
- cond, expr));
- if (zero_p (e))
+ te = expand_simple_operations (expr);
+
+ /* Check whether COND ==> EXPR. */
+ notcond = invert_truthvalue (cond);
+ e = fold_binary (TRUTH_OR_EXPR, boolean_type_node, notcond, te);
+ if (nonzero_p (e))
+ return e;
+
+ /* Check whether COND ==> not EXPR. */
+ e = fold_binary (TRUTH_AND_EXPR, boolean_type_node, cond, te);
+ if (e && zero_p (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)
+{
+ edge e;
+ basic_block bb;
+ tree exp, cond;
+
+ if (TREE_CODE (expr) == INTEGER_CST)
+ return expr;
+
+ for (bb = loop->header;
+ bb != ENTRY_BLOCK_PTR;
+ 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;
+
+ cond = COND_EXPR_COND (last_stmt (e->src));
+ 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;
+ }
+
+ return expr;
+}
+
+/* Tries to simplify EXPR using the evolutions of the loop invariants
+ in the superloops of LOOP. Returns the simplified expression
+ (or EXPR unchanged, if no simplification was possible). */
+
+static tree
+simplify_using_outer_evolutions (struct loop *loop, tree expr)
+{
+ enum tree_code code = TREE_CODE (expr);
+ bool changed;
+ tree e, e0, e1, e2;
+
+ if (is_gimple_min_invariant (expr))
+ return expr;
+
+ if (code == TRUTH_OR_EXPR
+ || code == TRUTH_AND_EXPR
+ || code == COND_EXPR)
+ {
+ changed = false;
+
+ e0 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 0));
+ if (TREE_OPERAND (expr, 0) != e0)
+ changed = true;
+
+ e1 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 1));
+ if (TREE_OPERAND (expr, 1) != e1)
+ changed = true;
+
+ if (code == COND_EXPR)
+ {
+ e2 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 2));
+ if (TREE_OPERAND (expr, 2) != e2)
+ changed = true;
+ }
+ else
+ e2 = NULL_TREE;
+
+ if (changed)
+ {
+ if (code == COND_EXPR)
+ expr = fold_build3 (code, boolean_type_node, e0, e1, e2);
+ else
+ expr = fold_build2 (code, boolean_type_node, e0, e1);
+ }
+
+ return expr;
+ }
+
+ e = instantiate_parameters (loop, expr);
+ if (is_gimple_min_invariant (e))
return e;
return 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).*/
+/* Returns true if EXIT is the only possible exit from LOOP. */
-static tree
-simplify_using_initial_conditions (struct loop *loop, tree expr,
- tree *conds_used)
+static bool
+loop_only_exit_p (struct loop *loop, edge exit)
{
- edge e;
- basic_block bb;
- tree exp, cond;
+ basic_block *body;
+ block_stmt_iterator bsi;
+ unsigned i;
+ tree call;
- if (TREE_CODE (expr) == INTEGER_CST)
- return expr;
+ if (exit != loop->single_exit)
+ return false;
- for (bb = loop->header;
- bb != ENTRY_BLOCK_PTR;
- bb = get_immediate_dominator (CDI_DOMINATORS, bb))
+ body = get_loop_body (loop);
+ for (i = 0; i < loop->num_nodes; i++)
{
- e = EDGE_PRED (bb, 0);
- if (EDGE_COUNT (bb->preds) > 1)
- continue;
-
- if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
- continue;
-
- cond = COND_EXPR_COND (last_stmt (e->src));
- 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;
+ for (bsi = bsi_start (body[0]); !bsi_end_p (bsi); bsi_next (&bsi))
+ {
+ call = get_call_expr_in (bsi_stmt (bsi));
+ if (call && TREE_SIDE_EFFECTS (call))
+ {
+ free (body);
+ return false;
+ }
+ }
}
- return expr;
+ 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. */
+ 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)
+ struct tree_niter_desc *niter,
+ bool warn)
{
tree stmt, cond, type;
- tree op0, base0, step0;
- tree op1, base1, step1;
+ tree op0, op1;
enum tree_code code;
+ affine_iv iv0, iv1;
if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src))
return false;
&& !POINTER_TYPE_P (type))
return false;
- if (!simple_iv (loop, stmt, op0, &base0, &step0))
+ if (!simple_iv (loop, stmt, op0, &iv0, false))
return false;
- if (!simple_iv (loop, stmt, op1, &base1, &step1))
+ if (!simple_iv (loop, stmt, op1, &iv1, false))
return false;
- niter->niter = NULL_TREE;
- number_of_iterations_cond (type, base0, step0, code, base1, step1,
- niter);
- if (!niter->niter)
+ iv0.base = expand_simple_operations (iv0.base);
+ iv1.base = expand_simple_operations (iv1.base);
+ if (!number_of_iterations_cond (type, &iv0, code, &iv1, niter,
+ loop_only_exit_p (loop, exit)))
return false;
- niter->assumptions = simplify_using_outer_evolutions (loop,
- niter->assumptions);
- niter->may_be_zero = simplify_using_outer_evolutions (loop,
- niter->may_be_zero);
- niter->niter = simplify_using_outer_evolutions (loop, niter->niter);
+ if (optimize >= 3)
+ {
+ niter->assumptions = simplify_using_outer_evolutions (loop,
+ niter->assumptions);
+ niter->may_be_zero = simplify_using_outer_evolutions (loop,
+ niter->may_be_zero);
+ niter->niter = simplify_using_outer_evolutions (loop, niter->niter);
+ }
niter->additional_info = boolean_true_node;
niter->assumptions
= simplify_using_initial_conditions (loop,
niter->may_be_zero,
&niter->additional_info);
- return integer_onep (niter->assumptions);
+
+ 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 = EXPR_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 (!zero_p (iv1.step)
+ ? (zero_p (iv0.step)
+ && (integer_onep (iv1.step) || integer_all_onesp (iv1.step)))
+ : (iv0.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,
+ expression giving number of iterations is returned and *EXIT is
+ set to the edge from that the information is obtained. Otherwise
+ chrec_dont_know is returned. */
+
+tree
+find_loop_niter (struct loop *loop, edge *exit)
+{
+ unsigned n_exits, i;
+ edge *exits = get_loop_exit_edges (loop, &n_exits);
+ edge ex;
+ tree niter = NULL_TREE, aniter;
+ struct tree_niter_desc desc;
+
+ *exit = NULL;
+ for (i = 0; i < n_exits; i++)
+ {
+ ex = exits[i];
+ if (!just_once_each_iteration_p (loop, ex->src))
+ continue;
+
+ if (!number_of_iterations_exit (loop, ex, &desc, false))
+ continue;
+
+ if (nonzero_p (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);
+ *exit = ex;
+ break;
+ }
+
+ if (!zero_p (desc.may_be_zero))
+ continue;
+
+ aniter = desc.niter;
+
+ if (!niter)
+ {
+ /* Nothing recorded yet. */
+ niter = aniter;
+ *exit = ex;
+ continue;
+ }
+
+ /* Prefer constants, the lower the better. */
+ if (TREE_CODE (aniter) != INTEGER_CST)
+ continue;
+
+ if (TREE_CODE (niter) != INTEGER_CST)
+ {
+ niter = aniter;
+ *exit = ex;
+ continue;
+ }
+
+ if (tree_int_cst_lt (aniter, niter))
+ {
+ niter = aniter;
+ *exit = ex;
+ continue;
+ }
+ }
+ free (exits);
+
+ return niter ? niter : chrec_dont_know;
}
/*
chain_of_csts_start (struct loop *loop, tree x)
{
tree stmt = SSA_NAME_DEF_STMT (x);
+ tree use;
basic_block bb = bb_for_stmt (stmt);
- use_optype uses;
if (!bb
|| !flow_bb_inside_loop_p (loop, bb))
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)
+ if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
return NULL_TREE;
- if (NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) > 0)
+ if (SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_DEF) == NULL_DEF_OPERAND_P)
return NULL_TREE;
- if (NUM_DEFS (STMT_DEF_OPS (stmt)) > 1)
- return NULL_TREE;
- uses = STMT_USE_OPS (stmt);
- if (NUM_USES (uses) != 1)
+
+ use = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
+ if (use == NULL_USE_OPERAND_P)
return NULL_TREE;
- return chain_of_csts_start (loop, USE_OP (uses, 0));
+ return chain_of_csts_start (loop, use);
}
/* Determines whether the expression X is derived from a result of a phi node
get_val_for (tree x, tree base)
{
tree stmt, nx, val;
- use_optype uses;
use_operand_p op;
+ ssa_op_iter iter;
if (!x)
return base;
if (TREE_CODE (stmt) == PHI_NODE)
return base;
- uses = STMT_USE_OPS (stmt);
- op = USE_OP_PTR (uses, 0);
-
- 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);
+ FOR_EACH_SSA_USE_OPERAND (op, stmt, iter, SSA_OP_USE)
+ {
+ 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);
+ /* only iterate loop once. */
+ return val;
+ }
- return val;
+ /* Should never reach here. */
+ gcc_unreachable();
}
/* Tries to count the number of iterations of LOOP till it exits by EXIT
for (j = 0; j < 2; j++)
aval[j] = get_val_for (op[j], val[j]);
- acnd = fold (build2 (cmp, boolean_type_node, aval[0], aval[1]));
- if (zero_p (acnd))
+ acnd = fold_binary (cmp, boolean_type_node, aval[0], aval[1]);
+ if (acnd && zero_p (acnd))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
continue;
aniter = loop_niter_by_eval (loop, ex);
- if (chrec_contains_undetermined (aniter)
- || TREE_CODE (aniter) != INTEGER_CST)
+ if (chrec_contains_undetermined (aniter))
continue;
if (niter
- && !nonzero_p (fold (build2 (LT_EXPR, boolean_type_node,
- aniter, niter))))
+ && !tree_int_cst_lt (aniter, niter))
continue;
niter = aniter;
loop->bounds = elt;
}
+/* Initialize LOOP->ESTIMATED_NB_ITERATIONS with the lowest safe
+ approximation of the number of iterations for LOOP. */
+
+static void
+compute_estimated_nb_iterations (struct loop *loop)
+{
+ struct nb_iter_bound *bound;
+
+ for (bound = loop->bounds; bound; bound = bound->next)
+ if (TREE_CODE (bound->bound) == INTEGER_CST
+ /* Update only when there is no previous estimation. */
+ && (chrec_contains_undetermined (loop->estimated_nb_iterations)
+ /* Or when the current estimation is smaller. */
+ || tree_int_cst_lt (bound->bound, loop->estimated_nb_iterations)))
+ loop->estimated_nb_iterations = bound->bound;
+}
+
+/* The following analyzers are extracting informations on the bounds
+ of LOOP from the following undefined behaviors:
+
+ - data references should not access elements over the statically
+ allocated size,
+
+ - signed variables should not overflow when flag_wrapv is not set.
+*/
+
+static void
+infer_loop_bounds_from_undefined (struct loop *loop)
+{
+ unsigned i;
+ basic_block bb, *bbs;
+ block_stmt_iterator bsi;
+
+ bbs = get_loop_body (loop);
+
+ for (i = 0; i < loop->num_nodes; i++)
+ {
+ bb = bbs[i];
+
+ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ {
+ tree stmt = bsi_stmt (bsi);
+
+ switch (TREE_CODE (stmt))
+ {
+ case MODIFY_EXPR:
+ {
+ tree op0 = TREE_OPERAND (stmt, 0);
+ tree op1 = TREE_OPERAND (stmt, 1);
+
+ /* For each array access, analyze its access function
+ and record a bound on the loop iteration domain. */
+ if (TREE_CODE (op1) == ARRAY_REF
+ && !array_ref_contains_indirect_ref (op1))
+ estimate_iters_using_array (stmt, op1);
+
+ if (TREE_CODE (op0) == ARRAY_REF
+ && !array_ref_contains_indirect_ref (op0))
+ estimate_iters_using_array (stmt, op0);
+
+ /* For each signed type variable in LOOP, analyze its
+ scalar evolution and record a bound of the loop
+ based on the type's ranges. */
+ else if (!flag_wrapv && TREE_CODE (op0) == SSA_NAME)
+ {
+ tree init, step, diff, estimation;
+ tree scev = instantiate_parameters
+ (loop, analyze_scalar_evolution (loop, op0));
+ tree type = chrec_type (scev);
+ tree utype;
+
+ if (chrec_contains_undetermined (scev)
+ || TYPE_UNSIGNED (type))
+ break;
+
+ init = initial_condition_in_loop_num (scev, loop->num);
+ step = evolution_part_in_loop_num (scev, loop->num);
+
+ if (init == NULL_TREE
+ || step == NULL_TREE
+ || TREE_CODE (init) != INTEGER_CST
+ || TREE_CODE (step) != INTEGER_CST
+ || TYPE_MIN_VALUE (type) == NULL_TREE
+ || TYPE_MAX_VALUE (type) == NULL_TREE)
+ break;
+
+ utype = unsigned_type_for (type);
+ if (tree_int_cst_lt (step, integer_zero_node))
+ diff = fold_build2 (MINUS_EXPR, utype, init,
+ TYPE_MIN_VALUE (type));
+ else
+ diff = fold_build2 (MINUS_EXPR, utype,
+ TYPE_MAX_VALUE (type), init);
+
+ if (!integer_zerop (step))
+ {
+ estimation = fold_build2 (CEIL_DIV_EXPR, utype, diff,
+ step);
+ record_estimate (loop, estimation, boolean_true_node,
+ stmt);
+ }
+ }
+
+ break;
+ }
+
+ case CALL_EXPR:
+ {
+ tree args;
+
+ for (args = TREE_OPERAND (stmt, 1); args;
+ args = TREE_CHAIN (args))
+ if (TREE_CODE (TREE_VALUE (args)) == ARRAY_REF
+ && !array_ref_contains_indirect_ref (TREE_VALUE (args)))
+ estimate_iters_using_array (stmt, TREE_VALUE (args));
+
+ break;
+ }
+
+ default:
+ break;
+ }
+ }
+
+ if (chrec_contains_undetermined (loop->estimated_nb_iterations))
+ compute_estimated_nb_iterations (loop);
+ }
+
+ free (bbs);
+}
+
/* Records estimates on numbers of iterations of LOOP. */
static void
unsigned i, n_exits;
struct tree_niter_desc niter_desc;
+ /* Give up if we already have tried to compute an estimation. */
+ if (loop->estimated_nb_iterations == chrec_dont_know
+ /* Or when we already have an estimation. */
+ || (loop->estimated_nb_iterations != NULL_TREE
+ && TREE_CODE (loop->estimated_nb_iterations) == INTEGER_CST))
+ return;
+ else
+ loop->estimated_nb_iterations = chrec_dont_know;
+
exits = get_loop_exit_edges (loop, &n_exits);
for (i = 0; i < n_exits; i++)
{
- if (!number_of_iterations_exit (loop, exits[i], &niter_desc))
+ if (!number_of_iterations_exit (loop, exits[i], &niter_desc, false))
continue;
niter = niter_desc.niter;
}
free (exits);
- /* Analyzes the bounds of arrays accessed in the loop. */
- if (loop->estimated_nb_iterations == NULL_TREE)
- {
- varray_type datarefs;
- VARRAY_GENERIC_PTR_INIT (datarefs, 3, "datarefs");
- find_data_references_in_loop (loop, &datarefs);
- free_data_refs (datarefs);
- }
+ if (chrec_contains_undetermined (loop->estimated_nb_iterations))
+ infer_loop_bounds_from_undefined (loop);
}
/* Records estimates on numbers of iterations of LOOPS. */
a = fold_convert (type, a);
b = fold_convert (type, b);
- if (nonzero_p (fold (build2 (EQ_EXPR, boolean_type_node, a, b))))
+ if (nonzero_p (fold_binary (EQ_EXPR, boolean_type_node, a, b)))
return 0;
- if (nonzero_p (fold (build2 (LT_EXPR, boolean_type_node, a, b))))
+ if (nonzero_p (fold_binary (LT_EXPR, boolean_type_node, a, b)))
return 1;
- if (nonzero_p (fold (build2 (GT_EXPR, boolean_type_node, a, b))))
+ if (nonzero_p (fold_binary (GT_EXPR, boolean_type_node, a, b)))
return -1;
return 2;
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.
+/* Return true when it is possible to prove that the induction
+ variable does not wrap: vary outside the type specified bounds.
+ Checks whether BOUND < VALID_NITER that means in the context of iv
+ conversion that all the iterations in the loop are safe: not
+ producing wraps.
+
+ The statement NITER_BOUND->AT_STMT is executed at most
+ NITER_BOUND->BOUND times in the loop.
- ADDITIONAL is the additional condition recorded for operands of the bound.
- This is useful in the following case, created by loop header copying:
+ NITER_BOUND->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)
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
+proved_non_wrapping_p (tree at_stmt,
+ struct nb_iter_bound *niter_bound,
+ tree new_type,
+ tree valid_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;
+ tree bound = niter_bound->bound;
+ enum tree_code cmp;
+
+ if (TYPE_PRECISION (new_type) > TYPE_PRECISION (TREE_TYPE (bound)))
+ bound = fold_convert (unsigned_type_for (new_type), bound);
+ else
+ valid_niter = fold_convert (TREE_TYPE (bound), valid_niter);
+
+ /* Give up if BOUND was not folded to an INTEGER_CST, as in PR23434. */
+ if (TREE_CODE (bound) != INTEGER_CST)
+ return false;
+
+ /* After the statement niter_bound->at_stmt we know that anything is
+ executed at most BOUND times. */
+ if (at_stmt && stmt_dominates_stmt_p (niter_bound->at_stmt, at_stmt))
+ cmp = GE_EXPR;
+ /* Before the statement niter_bound->at_stmt we know that anything
+ is executed at most BOUND + 1 times. */
+ else
+ cmp = GT_EXPR;
+
+ cond = fold_binary (cmp, boolean_type_node, valid_niter, bound);
+ if (nonzero_p (cond))
+ return true;
+
+ cond = build2 (cmp, boolean_type_node, valid_niter, bound);
+ /* Try taking additional conditions into account. */
+ cond = fold_binary (TRUTH_OR_EXPR, boolean_type_node,
+ invert_truthvalue (niter_bound->additional),
+ cond);
+
+ if (nonzero_p (cond))
+ return true;
+
+ return false;
+}
- 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)
+/* Checks whether it is correct to count the induction variable BASE +
+ STEP * I at AT_STMT in a wider type NEW_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 NEW_TYPE, otherwise
+ return NULL_TREE. */
+
+static tree
+convert_step_widening (struct loop *loop, tree new_type, tree base, tree step,
+ tree at_stmt)
+{
+ struct nb_iter_bound *bound;
+ tree base_in_new_type, base_plus_step_in_new_type, step_in_new_type;
+ tree delta, step_abs;
+ tree unsigned_type, valid_niter;
+
+ /* Compute the new step. For example, {(uchar) 100, +, (uchar) 240}
+ is converted to {(uint) 100, +, (uint) 0xfffffff0} in order to
+ keep the values of the induction variable unchanged: 100, 84, 68,
+ ...
+
+ Another example is: (uint) {(uchar)100, +, (uchar)3} is converted
+ to {(uint)100, +, (uint)3}.
+
+ Before returning the new step, verify that the number of
+ iterations is less than DELTA / STEP_ABS (i.e. in the previous
+ example (256 - 100) / 3) such that the iv does not wrap (in which
+ case the operations are too difficult to be represented and
+ handled: the values of the iv should be taken modulo 256 in the
+ wider type; this is not implemented). */
+ base_in_new_type = fold_convert (new_type, base);
+ base_plus_step_in_new_type =
+ fold_convert (new_type,
+ fold_build2 (PLUS_EXPR, TREE_TYPE (base), base, step));
+ step_in_new_type = fold_build2 (MINUS_EXPR, new_type,
+ base_plus_step_in_new_type,
+ base_in_new_type);
+
+ if (TREE_CODE (step_in_new_type) != INTEGER_CST)
return NULL_TREE;
- switch (compare_trees (bplusstep, b))
+ switch (compare_trees (base_plus_step_in_new_type, base_in_new_type))
{
case -1:
- extreme = upper_bound_in_type (type, inner_type);
- delta = fold (build2 (MINUS_EXPR, type, extreme, b));
- new_step_abs = new_step;
- break;
+ {
+ tree extreme = upper_bound_in_type (new_type, TREE_TYPE (base));
+ delta = fold_build2 (MINUS_EXPR, new_type, extreme,
+ base_in_new_type);
+ step_abs = step_in_new_type;
+ 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;
+ {
+ tree extreme = lower_bound_in_type (new_type, TREE_TYPE (base));
+ delta = fold_build2 (MINUS_EXPR, new_type, base_in_new_type,
+ extreme);
+ step_abs = fold_build1 (NEGATE_EXPR, new_type, step_in_new_type);
+ break;
+ }
case 0:
- return new_step;
+ return step_in_new_type;
default:
return NULL_TREE;
}
- unsigned_type = unsigned_type_for (type);
+ unsigned_type = unsigned_type_for (new_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));
+ step_abs = fold_convert (unsigned_type, step_abs);
+ valid_niter = fold_build2 (FLOOR_DIV_EXPR, unsigned_type,
+ delta, 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))
+ estimate_numbers_of_iterations_loop (loop);
+ for (bound = loop->bounds; bound; bound = bound->next)
+ if (proved_non_wrapping_p (at_stmt, bound, new_type, valid_niter))
+ return step_in_new_type;
+
+ /* Fail when the loop has no bound estimations, or when no bound can
+ be used for verifying the conversion. */
+ return NULL_TREE;
+}
+
+/* Returns true when VAR is used in pointer arithmetics. DEPTH is
+ used for limiting the search. */
+
+static bool
+used_in_pointer_arithmetic_p (tree var, int depth)
+{
+ use_operand_p use_p;
+ imm_use_iterator iter;
+
+ if (depth == 0
+ || TREE_CODE (var) != SSA_NAME
+ || !has_single_use (var))
+ return false;
+
+ FOR_EACH_IMM_USE_FAST (use_p, iter, var)
{
- /* After the statement OF we know that anything is executed at most
- BOUND times. */
- cond = build2 (GE_EXPR, boolean_type_node, valid_niter, bound);
+ tree stmt = USE_STMT (use_p);
+
+ if (stmt && TREE_CODE (stmt) == MODIFY_EXPR)
+ {
+ tree rhs = TREE_OPERAND (stmt, 1);
+
+ if (TREE_CODE (rhs) == NOP_EXPR
+ || TREE_CODE (rhs) == CONVERT_EXPR)
+ {
+ if (POINTER_TYPE_P (TREE_TYPE (rhs)))
+ return true;
+ return false;
+ }
+ else
+ return used_in_pointer_arithmetic_p (TREE_OPERAND (stmt, 0),
+ depth - 1);
+ }
}
- else
+ return false;
+}
+
+/* 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.
+
+ Initialize INIT_IS_MAX to true when the evolution goes from
+ INIT_IS_MAX to LOWER_BOUND_IN_TYPE, false in the contrary case.
+ When this property cannot be determined, UNKNOWN_MAX is set to
+ true. */
+
+bool
+scev_probably_wraps_p (tree type, tree base, tree step,
+ tree at_stmt, struct loop *loop,
+ bool *init_is_max, bool *unknown_max)
+{
+ struct nb_iter_bound *bound;
+ tree delta, step_abs;
+ tree unsigned_type, valid_niter;
+ tree base_plus_step, bpsps;
+ int cps, cpsps;
+
+ /* FIXME: The following code will not be used anymore once
+ http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html is
+ committed.
+
+ If AT_STMT is a cast to unsigned that is later used for
+ referencing a memory location, it is followed by a pointer
+ conversion just after. Because pointers do not wrap, the
+ sequences that reference the memory do not wrap either. In the
+ following example, sequences corresponding to D_13 and to D_14
+ can be proved to not wrap because they are used for computing a
+ memory access:
+
+ 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;
+ */
+ if (at_stmt && TREE_CODE (at_stmt) == MODIFY_EXPR)
{
- /* Before the statement OF we know that anything is executed at most
- BOUND + 1 times. */
- cond = build2 (GT_EXPR, boolean_type_node, valid_niter, bound);
+ tree op0 = TREE_OPERAND (at_stmt, 0);
+ tree op1 = TREE_OPERAND (at_stmt, 1);
+ tree type_op1 = TREE_TYPE (op1);
+
+ if ((TYPE_UNSIGNED (type_op1)
+ && used_in_pointer_arithmetic_p (op0, 2))
+ || POINTER_TYPE_P (type_op1))
+ {
+ *unknown_max = true;
+ return false;
+ }
}
- cond = fold (cond);
- if (nonzero_p (cond))
- return new_step;
+ if (chrec_contains_undetermined (base)
+ || chrec_contains_undetermined (step)
+ || TREE_CODE (base) == REAL_CST
+ || TREE_CODE (step) == REAL_CST)
+ {
+ *unknown_max = true;
+ return true;
+ }
- /* Try taking additional conditions into account. */
- cond = build2 (TRUTH_OR_EXPR, boolean_type_node,
- invert_truthvalue (additional),
- cond);
- cond = fold (cond);
- if (nonzero_p (cond))
- return new_step;
+ *unknown_max = false;
+ base_plus_step = fold_build2 (PLUS_EXPR, type, base, step);
+ bpsps = fold_build2 (PLUS_EXPR, type, base_plus_step, step);
+ cps = compare_trees (base_plus_step, base);
+ cpsps = compare_trees (bpsps, base_plus_step);
- return NULL_TREE;
+ /* Check that the sequence is not wrapping in the first step: it
+ should have the same monotonicity for the first two steps. See
+ PR23410. */
+ if (cps != cpsps)
+ return true;
+
+ switch (cps)
+ {
+ case -1:
+ {
+ tree extreme = upper_bound_in_type (type, TREE_TYPE (base));
+ delta = fold_build2 (MINUS_EXPR, type, extreme, base);
+ step_abs = step;
+ *init_is_max = false;
+ break;
+ }
+
+ case 1:
+ {
+ tree extreme = lower_bound_in_type (type, TREE_TYPE (base));
+ delta = fold_build2 (MINUS_EXPR, type, base, extreme);
+ step_abs = fold_build1 (NEGATE_EXPR, type, step);
+ *init_is_max = true;
+ break;
+ }
+
+ case 0:
+ /* This means step is equal to 0. This should not happen. It
+ could happen in convert step, but not here. Safely answer
+ don't know as in the default case. */
+
+ default:
+ *unknown_max = true;
+ return true;
+ }
+
+ /* If AT_STMT represents a cast operation, we may not be able to
+ take advantage of the undefinedness of signed type evolutions.
+
+ implement-c.texi states: "For conversion to a type of width
+ N, the value is reduced modulo 2^N to be within range of the
+ type;"
+
+ See PR 21959 for a test case. Essentially, given a cast
+ operation
+ unsigned char uc;
+ signed char sc;
+ ...
+ sc = (signed char) uc;
+ if (sc < 0)
+ ...
+
+ where uc and sc have the scev {0, +, 1}, we would consider uc to
+ wrap around, but not sc, because it is of a signed type. This
+ causes VRP to erroneously fold the predicate above because it
+ thinks that sc cannot be negative. */
+ if (at_stmt && TREE_CODE (at_stmt) == MODIFY_EXPR)
+ {
+ tree rhs = TREE_OPERAND (at_stmt, 1);
+ tree outer_t = TREE_TYPE (rhs);
+
+ if (!TYPE_UNSIGNED (outer_t)
+ && (TREE_CODE (rhs) == NOP_EXPR || TREE_CODE (rhs) == CONVERT_EXPR))
+ {
+ tree inner_t = TREE_TYPE (TREE_OPERAND (rhs, 0));
+
+ /* If the inner type is unsigned and its size and/or
+ precision are smaller to that of the outer type, then the
+ expression may wrap around. */
+ if (TYPE_UNSIGNED (inner_t)
+ && (TYPE_SIZE (inner_t) <= TYPE_SIZE (outer_t)
+ || TYPE_PRECISION (inner_t) <= TYPE_PRECISION (outer_t)))
+ {
+ *unknown_max = true;
+ return true;
+ }
+ }
+ }
+
+ /* After having set INIT_IS_MAX, we can return false: when not using
+ wrapping arithmetic, signed types don't wrap. */
+ if (!flag_wrapv && !TYPE_UNSIGNED (type))
+ return false;
+
+ unsigned_type = unsigned_type_for (type);
+ delta = fold_convert (unsigned_type, delta);
+ step_abs = fold_convert (unsigned_type, step_abs);
+ valid_niter = fold_build2 (FLOOR_DIV_EXPR, unsigned_type, delta, step_abs);
+
+ estimate_numbers_of_iterations_loop (loop);
+ for (bound = loop->bounds; bound; bound = bound->next)
+ if (proved_non_wrapping_p (at_stmt, bound, type, valid_niter))
+ return false;
+
+ /* At this point we still don't have a proof that the iv does not
+ overflow: give up. */
+ *unknown_max = true;
+ return true;
}
-/* 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 the conversion to NEW_TYPE of the STEP of an induction
+ variable BASE + STEP * I at AT_STMT. When it fails, return
+ NULL_TREE. */
tree
-can_count_iv_in_wider_type (struct loop *loop, tree type, tree base, tree step,
- tree at_stmt)
+convert_step (struct loop *loop, tree new_type, tree base, tree step,
+ tree at_stmt)
{
- struct nb_iter_bound *bound;
- tree new_step;
+ tree res, base_type;
- for (bound = loop->bounds; bound; bound = bound->next)
+ if (chrec_contains_undetermined (base)
+ || chrec_contains_undetermined (step))
+ return NULL_TREE;
+
+ base_type = TREE_TYPE (base);
+
+ /* When not using wrapping arithmetic, signed types don't wrap. */
+ if (!flag_wrapv && !TYPE_UNSIGNED (base_type))
+ goto do_convert_step;
+
+ if (TYPE_PRECISION (new_type) > TYPE_PRECISION (base_type))
+ return convert_step_widening (loop, new_type, base, step, at_stmt);
+
+ do_convert_step:
+
+ res = fold_convert (new_type, step);
+
+ if (TREE_CODE (res) == INTEGER_CST)
{
- new_step = can_count_iv_in_wider_type_bound (type, base, step,
- at_stmt,
- bound->bound,
- bound->additional,
- bound->at_stmt);
-
- if (new_step)
- return new_step;
+ TREE_OVERFLOW (res) = 0;
+ TREE_CONSTANT_OVERFLOW (res) = 0;
}
- return NULL_TREE;
+ return res;
}
/* 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->estimated_nb_iterations = NULL;
for (bound = loop->bounds; bound; bound = next)
{
next = bound->next;
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)
+{
+ struct nb_iter_bound *bound;
+
+ loop->nb_iterations = simplify_replace_tree (loop->nb_iterations, name, val);
+ loop->estimated_nb_iterations
+ = simplify_replace_tree (loop->estimated_nb_iterations, name, val);
+ for (bound = loop->bounds; bound; bound = bound->next)
+ {
+ bound->bound = simplify_replace_tree (bound->bound, name, val);
+ bound->additional = simplify_replace_tree (bound->additional, name, val);
+ }
+}
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