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[Bug other/16798] New: PowerPC - Opportunity to use recording form instruction.
- From: "gcc-bugzilla at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 28 Jul 2004 17:00:52 -0000
- Subject: [Bug other/16798] New: PowerPC - Opportunity to use recording form instruction.
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
Description:
A non-optimal code sequence is illustraded. The recording form of an instruction could be used allowing for the elimination of a compare. Duplicate using gcc 3.5 and command line:
gcc -O3 -m64 -c test.c
Testcase:
long int i, j;
int foo ()
{
j = (i>>52);
if (j< 0) {
i = 10;
} else {
i = 20;
};
return i;
}
Assembly:
.foo:
ld 11,.LC0@toc(2)
ld 9,.LC1@toc(2)
ld 0,0(11)
sradi 0,0,52 <-- Use the recording form of sradi
cmpdi 7,0,0 <-- and eliminate this compare.
std 0,0(9)
blt- 7,.L7
li 0,20
std 0,0(11)
lwa 3,4(11)
blr
.L7:
li 0,10
std 0,0(11)
lwa 3,4(11)
blr
--
Summary: PowerPC - Opportunity to use recording form instruction.
Product: gcc
Version: 3.5.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P1
Component: other
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: steinmtz at us dot ibm dot com
CC: gcc-bugs at gcc dot gnu dot org,steinmtz at us dot ibm
dot com
GCC build triplet: powerpc64-linux
GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16798