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cmd/dist: avoid using %ebx on i386.

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Or gcc (-fPIC) will complain:
cmd/dist/unix.c: In function ‘cansse2’
cmd/dist/unix.c:774: error: can't find a register in class ‘BREG’ while reloading ‘asm’
cmd/dist/unix.c:774: error: ‘asm’ operand has impossible constraints

This affects bootstrapping on native Darwin/386 where all code is
compiled with -fPIC.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7394047
This commit is contained in:
Shenghou Ma 2013-02-24 22:45:53 +08:00
parent c5f5df4d98
commit 89ec3a610d
1 changed files with 9 additions and 1 deletions
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10
src/cmd/dist/unix.c vendored
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@ -770,7 +770,15 @@ sigillhand(int signum)
static void
__cpuid(int dst[4], int ax)
{
#if defined(__i386__) || defined(__x86_64__)
#ifdef __i386__
// we need to avoid ebx on i386 (esp. when -fPIC).
asm volatile(
"mov %%ebx, %%edi\n\t"
"cpuid\n\t"
"xchgl %%ebx, %%edi"
: "=a" (dst[0]), "=D" (dst[1]), "=c" (dst[2]), "=d" (dst[3])
: "0" (ax));
#elif defined(__x86_64__)
asm volatile("cpuid"
: "=a" (dst[0]), "=b" (dst[1]), "=c" (dst[2]), "=d" (dst[3])
: "0" (ax));