/* 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;
In case we are unable to determine number of iterations, contents of
this structure is unchanged. */
-void
+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)
if (code != NE_EXPR)
return;
- step0 = EXEC_BINARY (MINUS_EXPR, type, step0, step1);
+ step0 = fold_binary_to_constant (MINUS_EXPR, type, step0, step1);
step1 = NULL_TREE;
}
/* Ignore loops of while (i-- < 10) type. */
if (code != NE_EXPR)
{
- if (step0 && !tree_expr_nonnegative_p (step0))
+ if (step0 && tree_int_cst_sign_bit (step0))
return;
- if (!zero_p (step1) && tree_expr_nonnegative_p (step1))
+ if (!zero_p (step1) && !tree_int_cst_sign_bit (step1))
return;
}
if (zero_p (step0))
{
if (mmax)
- assumption = fold (build2 (EQ_EXPR, boolean_type_node, base0, 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)));
+ 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));
+ 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)));
+ base1 = fold_build2 (MINUS_EXPR, type, base1,
+ build_int_cst_type (type, 1));
}
noloop_assumptions = assumption;
code = LE_EXPR;
if (code != NE_EXPR)
{
if (zero_p (step0))
- step = EXEC_UNARY (NEGATE_EXPR, type, step1);
+ 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));
+ delta = fold_build2 (MINUS_EXPR, type, base1, base0);
+ delta = fold_build2 (FLOOR_MOD_EXPR, type, delta, step);
may_xform = boolean_false_node;
if (TREE_CODE (delta) == INTEGER_CST)
{
- tmp = EXEC_BINARY (MINUS_EXPR, type, step,
- build_int_cst_type (type, 1));
+ tmp = fold_binary_to_constant (MINUS_EXPR, type, step,
+ build_int_cst_type (type, 1));
if (was_sharp
&& operand_equal_p (delta, tmp, 0))
{
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));
+ 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
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_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 (zero_p (step0))
{
- base0 = build2 (PLUS_EXPR, type, base0, delta);
- base0 = fold (build2 (MINUS_EXPR, type, base0, step));
+ base0 = fold_build2 (PLUS_EXPR, type, base0, delta);
+ base0 = fold_build2 (MINUS_EXPR, type, base0, step);
}
else
{
- base1 = build2 (MINUS_EXPR, type, base1, delta);
- base1 = fold (build2 (PLUS_EXPR, type, base1, step));
+ base1 = fold_build2 (MINUS_EXPR, type, base1, delta);
+ base1 = fold_build2 (PLUS_EXPR, type, base1, step);
}
- assumption = fold (build2 (GT_EXPR, boolean_type_node, base0, base1));
- noloop_assumptions = fold (build2 (TRUTH_OR_EXPR, boolean_type_node,
- noloop_assumptions, assumption));
+ 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;
}
}
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));
+ base1 = fold_build2 (MINUS_EXPR, type, base1, base0);
base0 = NULL_TREE;
if (!zero_p (step1))
- step0 = EXEC_UNARY (NEGATE_EXPR, type, step1);
+ step0 = fold_unary_to_constant (NEGATE_EXPR, type, step1);
step1 = NULL_TREE;
- if (!tree_expr_nonnegative_p (fold_convert (signed_niter_type, step0)))
+ if (tree_int_cst_sign_bit (fold_convert (signed_niter_type, step0)))
{
- step0 = EXEC_UNARY (NEGATE_EXPR, type, step0);
- base1 = fold (build1 (NEGATE_EXPR, type, base1));
+ step0 = fold_unary_to_constant (NEGATE_EXPR, type, step0);
+ base1 = fold_build1 (NEGATE_EXPR, type, base1);
}
base1 = fold_convert (niter_type, base1);
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);
+ 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));
+ 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));
+ 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);
}
else
{
{
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));
+ 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));
+ 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
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));
+ 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));
+ 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)));
+ 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;
}
return;
}
-/* 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)
+/* 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. */
+
+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)
{
- enum tree_code code = TREE_CODE (expr);
- bool changed;
- tree e, e0, e1, e2;
+ tree niter_type = unsigned_type_for (type), mmax, mmin;
- if (is_gimple_min_invariant (expr))
- return expr;
+ /* Make < comparison from > ones. */
+ if (code == GE_EXPR
+ || code == GT_EXPR)
+ {
+ SWAP (base0, base1);
+ SWAP (step0, step1);
+ code = swap_tree_comparison (code);
+ }
- if (code == TRUTH_OR_EXPR
- || code == TRUTH_AND_EXPR
- || code == COND_EXPR)
+ switch (code)
{
- changed = false;
+ case NE_EXPR:
+ if (zero_p (step0))
+ {
+ if (zero_p (step1))
+ return false;
+ SWAP (base0, base1);
+ SWAP (step0, step1);
+ }
+ else if (!zero_p (step1))
+ return false;
- e0 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 0));
- if (TREE_OPERAND (expr, 0) != e0)
- changed = true;
+ if (integer_onep (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, 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);
+ }
+ else
+ return false;
- e1 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 1));
- if (TREE_OPERAND (expr, 1) != e1)
- changed = true;
+ break;
- if (code == COND_EXPR)
+ case LT_EXPR:
+ if ((step0 && integer_onep (step0) && zero_p (step1))
+ || (step1 && integer_all_onesp (step1) && zero_p (step0)))
{
- e2 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 2));
- if (TREE_OPERAND (expr, 2) != e2)
- changed = true;
+ /* for (i = base0; i < base1; i++)
+
+ or
+
+ for (i = base1; i > base0; i--).
+
+ In both cases # of iterations is base1 - base0. */
+
+ 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);
}
else
- e2 = NULL_TREE;
+ return false;
+ break;
- if (changed)
+ case LE_EXPR:
+ if (POINTER_TYPE_P (type))
{
- if (code == COND_EXPR)
- expr = build3 (code, boolean_type_node, e0, e1, e2);
+ /* We assume pointer arithmetic never overflows. */
+ mmin = mmax = NULL_TREE;
+ }
+ else
+ {
+ mmin = TYPE_MIN_VALUE (type);
+ mmax = TYPE_MAX_VALUE (type);
+ }
+
+ 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
- expr = build2 (code, boolean_type_node, e0, e1);
- expr = fold (expr);
+ 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
+ return false;
- return expr;
+ niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
+ base0, base1);
+ niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
+ break;
+
+ default:
+ gcc_unreachable ();
}
- e = instantiate_parameters (loop, expr);
- if (is_gimple_min_invariant (e))
- return e;
+ niter->niter = fold_convert (niter_type, niter->niter);
+ niter->additional_info = boolean_true_node;
+ return true;
+}
- return expr;
+/* Substitute NEW for OLD in EXPR and fold the result. */
+
+static tree
+simplify_replace_tree (tree expr, tree old, tree new)
+{
+ unsigned i, n;
+ tree ret = NULL_TREE, e, se;
+
+ if (!expr)
+ return NULL_TREE;
+
+ if (expr == old
+ || operand_equal_p (expr, old, 0))
+ return unshare_expr (new);
+
+ if (!EXPR_P (expr))
+ return expr;
+
+ n = TREE_CODE_LENGTH (TREE_CODE (expr));
+ for (i = 0; i < n; i++)
+ {
+ e = TREE_OPERAND (expr, i);
+ se = simplify_replace_tree (e, old, new);
+ if (e == se)
+ continue;
+
+ if (!ret)
+ ret = copy_node (expr);
+
+ TREE_OPERAND (ret, i) = se;
+ }
+
+ 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;
}
+ /* In case COND is equality, we may be able to simplify EXPR by copy/constant
+ propagation, and vice versa. Fold does not handle this, since it is
+ considered too expensive. */
+ if (TREE_CODE (cond) == EQ_EXPR)
+ {
+ e0 = TREE_OPERAND (cond, 0);
+ e1 = TREE_OPERAND (cond, 1);
+
+ /* 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))
+ return e;
+
+ e = simplify_replace_tree (expr, e1, e0);
+ if (zero_p (e) || nonzero_p (e))
+ return e;
+ }
+ if (TREE_CODE (expr) == EQ_EXPR)
+ {
+ e0 = TREE_OPERAND (expr, 0);
+ e1 = TREE_OPERAND (expr, 1);
+
+ /* If e0 == e1 (EXPR) implies !COND, then EXPR cannot be true. */
+ e = simplify_replace_tree (cond, e0, e1);
+ if (zero_p (e))
+ return e;
+ e = simplify_replace_tree (cond, e1, e0);
+ if (zero_p (e))
+ return e;
+ }
+ if (TREE_CODE (expr) == NE_EXPR)
+ {
+ e0 = TREE_OPERAND (expr, 0);
+ e1 = TREE_OPERAND (expr, 1);
+
+ /* If e0 == e1 (!EXPR) implies !COND, then EXPR must be true. */
+ e = simplify_replace_tree (cond, e0, e1);
+ if (zero_p (e))
+ return boolean_true_node;
+ e = simplify_replace_tree (cond, e1, e0);
+ if (zero_p (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));
+ e = fold_binary (TRUTH_OR_EXPR, boolean_type_node, notcond, te);
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))
+ 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
bb != ENTRY_BLOCK_PTR;
bb = get_immediate_dominator (CDI_DOMINATORS, bb))
{
- e = EDGE_PRED (bb, 0);
- if (EDGE_COUNT (bb->preds) > 1)
+ if (!single_pred_p (bb))
continue;
+ e = single_pred_edge (bb);
if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
continue;
exp = tree_simplify_using_condition (cond, expr);
if (exp != expr)
- *conds_used = fold (build2 (TRUTH_AND_EXPR,
+ *conds_used = fold_build2 (TRUTH_AND_EXPR,
boolean_type_node,
*conds_used,
- cond));
+ 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;
+}
+
/* 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;
&& !POINTER_TYPE_P (type))
return false;
- if (!simple_iv (loop, stmt, op0, &base0, &step0))
+ if (!simple_iv (loop, stmt, op0, &base0, &step0, false))
return false;
- if (!simple_iv (loop, stmt, op1, &base1, &step1))
+ if (!simple_iv (loop, stmt, op1, &base1, &step1, false))
return false;
niter->niter = NULL_TREE;
- number_of_iterations_cond (type, base0, step0, code, base1, step1,
- niter);
- if (!niter->niter)
- 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);
+ /* 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))
+ {
+
+ number_of_iterations_cond (type, base0, step0, code, base1, step1,
+ niter);
+
+ if (!niter->niter)
+ return false;
+ }
+
+ 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 (step1 ? !step0 && (integer_onep (step1) || integer_all_onesp (step1))
+ : step0 && (integer_onep (step0) || integer_all_onesp (step0)))
+ 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)
+ if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
return NULL_TREE;
- if (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) > 0)
+ if (SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_DEF) == NULL_DEF_OPERAND_P)
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)
+
+ 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);
+
+ 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 base_type;
- for (bound = loop->bounds; bound; bound = bound->next)
- {
- 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;
- }
+ if (chrec_contains_undetermined (base)
+ || chrec_contains_undetermined (step))
+ return NULL_TREE;
- 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))
+ return fold_convert (new_type, step);
+
+ if (TYPE_PRECISION (new_type) > TYPE_PRECISION (base_type))
+ return convert_step_widening (loop, new_type, base, step, at_stmt);
+
+ return fold_convert (new_type, step);
}
/* 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);
+ }
+}
OSDN Git Service
