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re PR middle-end/68142 (unsafe association of multiplication)

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2015-10-29  Richard Biener  <rguenther@suse.de>

	PR middle-end/68142
	* fold-const.c (extract_muldiv_1): Avoid introducing undefined
	overflow.

	* c-c++-common/ubsan/pr68142.c: New testcase.

From-SVN: r229528
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Richard Biener 2015-10-29 14:10:31 +00:00 committed by Richard Biener
parent 957060b5c5
commit 55db37536f
4 changed files with 53 additions and 2 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2015-10-29 Richard Biener <rguenther@suse.de>
PR middle-end/68142
* fold-const.c (extract_muldiv_1): Avoid introducing undefined
overflow.
2015-10-29 Andrew MacLeod <amacleod@redhat.com>
* alias.c: Reorder #include statements and remove duplicates.

13
gcc/fold-const.c
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@ -6008,8 +6008,17 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
or (for divide and modulus) if it is a multiple of our constant. */
if (code == MULT_EXPR
|| wi::multiple_of_p (t, c, TYPE_SIGN (type)))
return const_binop (code, fold_convert (ctype, t),
fold_convert (ctype, c));
{
tree tem = const_binop (code, fold_convert (ctype, t),
fold_convert (ctype, c));
/* If the multiplication overflowed to INT_MIN then we lost sign
information on it and a subsequent multiplication might
spuriously overflow. See PR68142. */
if (TREE_OVERFLOW (tem)
&& wi::eq_p (tem, wi::min_value (TYPE_PRECISION (ctype), SIGNED)))
return NULL_TREE;
return tem;
}
break;
CASE_CONVERT: case NON_LVALUE_EXPR:

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2015-10-29 Richard Biener <rguenther@suse.de>
PR middle-end/68142
* c-c++-common/ubsan/pr68142.c: New testcase.
2015-10-29 Paolo Carlini <paolo.carlini@oracle.com>
PR c++/67845

31
gcc/testsuite/c-c++-common/ubsan/pr68142.c Normal file
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@ -0,0 +1,31 @@
/* { dg-do run } */
/* { dg-options "-fsanitize=undefined -fsanitize-undefined-trap-on-error" } */
int __attribute__((noinline,noclone))
h(int a)
{
return 2 * (a * (__INT_MAX__/2 + 1));
}
int __attribute__((noinline,noclone))
i(int a)
{
return (2 * a) * (__INT_MAX__/2 + 1);
}
int __attribute__((noinline,noclone))
j(int a, int b)
{
return (b * a) * (__INT_MAX__/2 + 1);
}
int __attribute__((noinline,noclone))
k(int a, int b)
{
return (2 * a) * b;
}
int main()
{
volatile int tem = h(-1);
tem = i(-1);
tem = j(-1, 2);
tem = k(-1, __INT_MAX__/2 + 1);
return 0;
}