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* [Bug tree-optimization/39683] New: -fstrict-overflow misses multiply in comparison
@ 2009-04-07 20:07 tkoenig at gcc dot gnu dot org
2009-04-07 20:14 ` [Bug tree-optimization/39683] " pinskia at gcc dot gnu dot org
2009-04-08 9:11 ` rguenth at gcc dot gnu dot org
0 siblings, 2 replies; 3+ messages in thread
From: tkoenig at gcc dot gnu dot org @ 2009-04-07 20:07 UTC (permalink / raw)
To: gcc-bugs
The shift isn't necessary. This could have
been re-coded as
return (a-b)<2;
with -fstrict-overflow.
$ cat ga.c
int foo(int a, int b)
{
return (a-b)*4 < 8;
}
$ gcc -S -O2 -fstrict-overflow ga.c
$ cat ga.s
.file "ga.c"
.text
.p2align 4,,15
.globl foo
.type foo, @function
foo:
pushl %ebp
movl %esp, %ebp
movl 8(%ebp), %eax
subl 12(%ebp), %eax
popl %ebp
sall $2, %eax
cmpl $7, %eax
setle %al
movzbl %al, %eax
ret
.size foo, .-foo
.ident "GCC: (GNU) 4.4.0 20090221 (experimental)"
.section .note.GNU-stack,"",@progbits
--
Summary: -fstrict-overflow misses multiply in comparison
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tkoenig at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39683
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/39683] -fstrict-overflow misses multiply in comparison
2009-04-07 20:07 [Bug tree-optimization/39683] New: -fstrict-overflow misses multiply in comparison tkoenig at gcc dot gnu dot org
@ 2009-04-07 20:14 ` pinskia at gcc dot gnu dot org
2009-04-08 9:11 ` rguenth at gcc dot gnu dot org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2009-04-07 20:14 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2009-04-07 20:14 -------
Related to PR 31096.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39683
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/39683] -fstrict-overflow misses multiply in comparison
2009-04-07 20:07 [Bug tree-optimization/39683] New: -fstrict-overflow misses multiply in comparison tkoenig at gcc dot gnu dot org
2009-04-07 20:14 ` [Bug tree-optimization/39683] " pinskia at gcc dot gnu dot org
@ 2009-04-08 9:11 ` rguenth at gcc dot gnu dot org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-04-08 9:11 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from rguenth at gcc dot gnu dot org 2009-04-08 09:11 -------
Confirmed.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
BugsThisDependsOn| |31096
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2009-04-08 09:11:25
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39683
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-04-08 9:11 UTC | newest]
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2009-04-07 20:07 [Bug tree-optimization/39683] New: -fstrict-overflow misses multiply in comparison tkoenig at gcc dot gnu dot org
2009-04-07 20:14 ` [Bug tree-optimization/39683] " pinskia at gcc dot gnu dot org
2009-04-08 9:11 ` rguenth at gcc dot gnu dot org
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