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re PR tree-optimization/83269 (Wrong constant folding)

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PR tree-optimization/83269
	* fold-const.c (fold_binary_loc): Perform (-A) - B -> (-B) - A
	subtraction in arg0's type if type is signed and arg0 is unsigned.
	Formatting fix.

	* gcc.c-torture/execute/pr83269.c: New test.

From-SVN: r255729
This commit is contained in:
Jakub Jelinek 2017-12-15 23:15:30 +01:00 committed by Jakub Jelinek
parent ea5869d324
commit 99ccf43c70
4 changed files with 35 additions and 6 deletions
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5
gcc/ChangeLog
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@ -1,5 +1,10 @@
2017-12-15 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/83269
* fold-const.c (fold_binary_loc): Perform (-A) - B -> (-B) - A
subtraction in arg0's type if type is signed and arg0 is unsigned.
Formatting fix.
Backported from mainline
2017-12-14 Jakub Jelinek <jakub@redhat.com>

19
gcc/fold-const.c
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@ -9123,8 +9123,8 @@ expr_not_equal_to (tree t, const wide_int &w)
return NULL_TREE. */
tree
fold_binary_loc (location_t loc,
enum tree_code code, tree type, tree op0, tree op1)
fold_binary_loc (location_t loc, enum tree_code code, tree type,
tree op0, tree op1)
{
enum tree_code_class kind = TREE_CODE_CLASS (code);
tree arg0, arg1, tem;
@ -9728,10 +9728,17 @@ fold_binary_loc (location_t loc,
case MINUS_EXPR:
/* (-A) - B -> (-B) - A where B is easily negated and we can swap. */
if (TREE_CODE (arg0) == NEGATE_EXPR
&& negate_expr_p (op1))
return fold_build2_loc (loc, MINUS_EXPR, type,
negate_expr (op1),
fold_convert_loc (loc, type,
&& negate_expr_p (op1)
/* If arg0 is e.g. unsigned int and type is int, then this could
introduce UB, because if A is INT_MIN at runtime, the original
expression can be well defined while the latter is not.
See PR83269. */
&& !(ANY_INTEGRAL_TYPE_P (type)
&& TYPE_OVERFLOW_UNDEFINED (type)
&& ANY_INTEGRAL_TYPE_P (TREE_TYPE (arg0))
&& !TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (arg0))))
return fold_build2_loc (loc, MINUS_EXPR, type, negate_expr (op1),
fold_convert_loc (loc, type,
TREE_OPERAND (arg0, 0)));
/* Fold __complex__ ( x, 0 ) - __complex__ ( 0, y ) to

3
gcc/testsuite/ChangeLog
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@ -1,5 +1,8 @@
2017-12-15 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/83269
* gcc.c-torture/execute/pr83269.c: New test.
PR tree-optimization/80631
* gcc.target/i386/avx2-pr80631.c: New test.

14
gcc/testsuite/gcc.c-torture/execute/pr83269.c Normal file
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@ -0,0 +1,14 @@
/* PR tree-optimization/83269 */
int
main ()
{
#if __SIZEOF_INT__ == 4 && __SIZEOF_LONG_LONG__ > 4 && __CHAR_BIT__ == 8
volatile unsigned char a = 1;
long long b = 0x80000000L;
int c = -((int)(-b) - (-0x7fffffff * a));
if (c != 1)
__builtin_abort ();
#endif
return 0;
}