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re PR middle-end/30322 (((-i-1) + i) +1) is turned into ~i + (i+1) and never into 0 on the tree level) 

PR middle-end/30322
	* fold-const.c (fold_binary): Fold X + ~X and ~X + X into -1 when
	we don't care about trapping overflow.  Only convert -A - 1 into ~A
	when we don't care about trapping overflow.

	* gcc.dg/fold-plusnot-1.c: New test case.

From-SVN: r120300
This commit is contained in:
Roger Sayle 2006-12-31 16:17:49 +00:00 committed by Roger Sayle
parent 7c2da05e60
commit 870aa1ebe0
4 changed files with 64 additions and 1 deletions
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7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2006-12-31 Roger Sayle <roger@eyesopen.com>
PR middle-end/30322
* fold-const.c (fold_binary): Fold X + ~X and ~X + X into -1 when
we don't care about trapping overflow. Only convert -A - 1 into ~A
when we don't care about trapping overflow.
2006-12-31 Richard Guenther <rguenther@suse.de> 2006-12-31 Richard Guenther <rguenther@suse.de>
PR middle-end/30338 PR middle-end/30338

23
gcc/fold-const.c
View File

@ -8662,6 +8662,26 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
if (integer_zerop (arg1)) if (integer_zerop (arg1))
return non_lvalue (fold_convert (type, arg0)); return non_lvalue (fold_convert (type, arg0));
/* ~X + X is -1. */
if (TREE_CODE (arg0) == BIT_NOT_EXPR
&& operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0)
&& !TYPE_TRAP_SIGNED (type))
{
t1 = build_int_cst (type, -1);
t1 = force_fit_type (t1, 0, false, false);
return omit_one_operand (type, t1, arg1);
}
/* X + ~X is -1. */
if (TREE_CODE (arg1) == BIT_NOT_EXPR
&& operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0)
&& !TYPE_TRAP_SIGNED (type))
{
t1 = build_int_cst (type, -1);
t1 = force_fit_type (t1, 0, false, false);
return omit_one_operand (type, t1, arg0);
}
/* If we are adding two BIT_AND_EXPR's, both of which are and'ing /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
with a constant, and the two constants have no bits in common, with a constant, and the two constants have no bits in common,
we should treat this as a BIT_IOR_EXPR since this may produce more we should treat this as a BIT_IOR_EXPR since this may produce more
@ -9002,7 +9022,8 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
/* Convert -A - 1 to ~A. */ /* Convert -A - 1 to ~A. */
if (INTEGRAL_TYPE_P (type) if (INTEGRAL_TYPE_P (type)
&& TREE_CODE (arg0) == NEGATE_EXPR && TREE_CODE (arg0) == NEGATE_EXPR
&& integer_onep (arg1)) && integer_onep (arg1)
&& !TYPE_TRAP_SIGNED (type))
return fold_build1 (BIT_NOT_EXPR, type, return fold_build1 (BIT_NOT_EXPR, type,
fold_convert (type, TREE_OPERAND (arg0, 0))); fold_convert (type, TREE_OPERAND (arg0, 0)));

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2006-12-31 Roger Sayle <roger@eyesopen.com>
PR middle-end/30322
* gcc.dg/fold-plusnot-1.c: New test case.
2006-12-31 Simon Martin <simartin@users.sourceforge.net> 2006-12-31 Simon Martin <simartin@users.sourceforge.net>
PR c++/29731 PR c++/29731

30
gcc/testsuite/gcc.dg/fold-plusnot-1.c Normal file
View File

@ -0,0 +1,30 @@
/* PR middle-end/30322 */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-original" } */
int test1(int a)
{
return a + ~a;
}
int test2(int b)
{
return ~b + b;
}
unsigned int test3(unsigned int c)
{
return c + ~c;
}
unsigned int test4(unsigned int d)
{
return ~d + d;
}
/* { dg-final { scan-tree-dump-times "\\+ a" 0 "original" } } */
/* { dg-final { scan-tree-dump-times "\\+ b" 0 "original" } } */
/* { dg-final { scan-tree-dump-times "\\+ c" 0 "original" } } */
/* { dg-final { scan-tree-dump-times "\\+ d" 0 "original" } } */
/* { dg-final { cleanup-tree-dump "original" } } */