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re PR middle-end/52578 (Fails to fold another size difference)

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2012-03-14  Richard Guenther  <rguenther@suse.de>

	PR middle-end/52578
	* fold-const.c (fold_unary_loc): Fold (T1)(T2)x to (T1)x if
	the outermost conversion is a sign-change only.
	(fold_binary_loc): Disregard widening and sign-changing
	conversions when we determine if two variables are equal
	for reassociation.
	* tree-ssa-forwprop.c (combine_conversions): Fold (T1)(T2)x to
	(T1)x if the outermost conversion is a sign-change only.

	* gcc.dg/pr52578.c: New testcase.

From-SVN: r185378
This commit is contained in:
Richard Guenther 2012-03-14 10:51:34 +00:00 • committed by Richard Biener
parent a1d3d84bdf
commit 1caf8dd66c
5 changed files with 54 additions and 7 deletions
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11
gcc/ChangeLog
View file

@ -1,3 +1,14 @@
2012-03-14 Richard Guenther <rguenther@suse.de>
PR middle-end/52578
* fold-const.c (fold_unary_loc): Fold (T1)(T2)x to (T1)x if
the outermost conversion is a sign-change only.
(fold_binary_loc): Disregard widening and sign-changing
conversions when we determine if two variables are equal
for reassociation.
* tree-ssa-forwprop.c (combine_conversions): Fold (T1)(T2)x to
(T1)x if the outermost conversion is a sign-change only.
2012-03-14 Uros Bizjak <ubizjak@gmail.com>
Revert:

22
gcc/fold-const.c
View file

@ -7843,10 +7843,13 @@ fold_unary_loc (location_t loc, enum tree_code code, tree type, tree op0)
return fold_build1_loc (loc, code, type, TREE_OPERAND (op0, 0));
/* If we have a sign-extension of a zero-extended value, we can
replace that by a single zero-extension. */
replace that by a single zero-extension. Likewise if the
final conversion does not change precision we can drop the
intermediate conversion. */
if (inside_int && inter_int && final_int
&& inside_prec < inter_prec && inter_prec < final_prec
&& inside_unsignedp && !inter_unsignedp)
&& ((inside_prec < inter_prec && inter_prec < final_prec
&& inside_unsignedp && !inter_unsignedp)
|| final_prec == inter_prec))
return fold_build1_loc (loc, code, type, TREE_OPERAND (op0, 0));
/* Two conversions in a row are not needed unless:
@ -10335,10 +10338,21 @@ fold_binary_loc (location_t loc,
if (TREE_CODE (tmp0) == NEGATE_EXPR)
tmp0 = TREE_OPERAND (tmp0, 0);
if (CONVERT_EXPR_P (tmp0)
&& INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (tmp0, 0)))
&& (TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (tmp0, 0)))
<= TYPE_PRECISION (type)))
tmp0 = TREE_OPERAND (tmp0, 0);
if (TREE_CODE (tmp1) == NEGATE_EXPR)
tmp1 = TREE_OPERAND (tmp1, 0);
if (CONVERT_EXPR_P (tmp1)
&& INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (tmp1, 0)))
&& (TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (tmp1, 0)))
<= TYPE_PRECISION (type)))
tmp1 = TREE_OPERAND (tmp1, 0);
/* The only case we can still associate with two variables
is if they are the same, modulo negation. */
is if they are the same, modulo negation and bit-pattern
preserving conversions. */
if (!operand_equal_p (tmp0, tmp1, 0))
ok = false;
}

5
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2012-03-14 Richard Guenther <rguenther@suse.de>
PR middle-end/52578
* gcc.dg/pr52578.c: New testcase.
2012-03-14 Jakub Jelinek <jakub@redhat.com>
PR c++/52521

14
gcc/testsuite/gcc.dg/pr52578.c Normal file
View file

@ -0,0 +1,14 @@
/* { dg-do compile } */
/* { dg-options "-fdump-tree-original" } */
long bar (long i)
{
return (long)((unsigned long)i + 2) - (long)i;
}
long foo (int i)
{
return (long)((unsigned long)i + 2) - (long)i;
}
/* { dg-final { scan-tree-dump-times "return 2;" 2 "original" } } */
/* { dg-final { cleanup-tree-dump "original" } } */

9
gcc/tree-ssa-forwprop.c
View file

@ -2285,10 +2285,13 @@ combine_conversions (gimple_stmt_iterator *gsi)
}
/* If we have a sign-extension of a zero-extended value, we can
replace that by a single zero-extension. */
replace that by a single zero-extension. Likewise if the
final conversion does not change precision we can drop the
intermediate conversion. */
if (inside_int && inter_int && final_int
&& inside_prec < inter_prec && inter_prec < final_prec
&& inside_unsignedp && !inter_unsignedp)
&& ((inside_prec < inter_prec && inter_prec < final_prec
&& inside_unsignedp && !inter_unsignedp)
|| final_prec == inter_prec))
{
gimple_assign_set_rhs1 (stmt, defop0);
update_stmt (stmt);