> /usr/local/gcc43/bin/gcc -v
Using built-in specs.
Target: i386-apple-darwin8.10.1
Configured with: ../gcc/configure --prefix=/usr/local/gcc43 --with-arch=nocona
--with-tune=nocona --with-gmp=/sw --with-system-zlib
--enable-languages=c,c++,objc,obj-c++
Thread model: posix
gcc version 4.3.0 20070925 (experimental) (GCC)
> /usr/local/gcc43/bin/gcc -Os -fno-pic -S sbb.c -fomit-frame-pointer
.text
.globl _cmpb_sbb
_cmpb_sbb:
subl $12, %esp
movl 16(%esp), %eax
movl 20(%esp), %ecx
xorl %edx, %edx
cmpl 24(%esp), %ecx
setb %dl
negl %edx
andl %ecx, %edx
subl %edx, %eax
addl $12, %esp
ret
.subsections_via_symbols
Source:
unsigned cmpb_sbb(unsigned a, unsigned b, unsigned c)
{
unsigned mask = -(b < c);
a -= b & mask;
return a;
}
"setb, negl" is the same as 0 - (0 + eflags.CF), so it can be replaced with
"sbb %edx, %edx".
This is useful for if-conversion, since it's the same as "if (b < c) a -= b;"
--
Summary: x86 missed opportunity for sbb
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: astrange at ithinksw dot com
GCC build triplet: i386-apple-darwin8.10.1
GCC host triplet: i386-apple-darwin8.10.1
GCC target triplet: i386-apple-darwin8.10.1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33555
