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[Bug rtl-optimization/45617] New: optimize bit shift+compare at RTL level
- From: "zsojka at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 9 Sep 2010 17:48:14 -0000
- Subject: [Bug rtl-optimization/45617] New: optimize bit shift+compare at RTL level
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
+++ This bug was initially created as a clone of Bug #20517 +++
>From comment #4:
----- testcase.c -----
_Bool foo(unsigned i)
{
return (i >> 5) > 10;
}
_Bool bar(unsigned i)
{
return i > (10 << 5) + 31;
}
int fooi(unsigned i)
{
return (i >> 5) > 10;
}
int bari(unsigned i)
{
return i > (10 << 5) + 31;
}
----------------------
Compiled with:
$ gcc-4.6.0-pre9999 tst6.c -O3 -S -m32 -fomit-frame-pointer
(svn r162190)
Results in:
foo:
movl 4(%esp), %eax
shrl $5, %eax
cmpl $10, %eax
seta %al
ret
bar:
cmpl $351, 4(%esp)
seta %al
ret
fooi:
movl 4(%esp), %eax
shrl $5, %eax
cmpl $10, %eax
seta %al
movzbl %al, %eax
ret
bari:
xorl %eax, %eax
cmpl $351, 4(%esp)
seta %al
ret
--
Summary: optimize bit shift+compare at RTL level
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: zsojka at seznam dot cz
GCC target triplet: x86(_64)-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45617