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[Bug middle-end/30364] [4.1/4.2/4.3 Regression] Wrong variable ranges due to constant folding
- From: "guillaume dot melquiond at ens-lyon dot fr" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 4 Jan 2007 10:15:16 -0000
- Subject: [Bug middle-end/30364] [4.1/4.2/4.3 Regression] Wrong variable ranges due to constant folding
- References: <bug-30364-7904@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #1 from guillaume dot melquiond at ens-lyon dot fr 2007-01-04 10:15 -------
Is it really a middle-end issue?
It could also be seen as a front-end issue, as it does produce "a + b - 40",
doesn't it? If the front-end had given "(a - 20) + (b - 20)" to the middle-end,
then the correct ranges would have been computed. When adjusting the testcase
in such a way, GCC does generate correct code:
int f(int a, int b)
{
if (a > 0x7FFFFFF0) return 0;
if (b > 0x7FFFFFF0) return 0;
int d = a - 20;
int e = b - 20;
int c = d + e;
return c > 0x7FFFFFF0;
}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30364