[golang-dev] code review 6962043: cmd/dist, cmd/8g: implement GO386=387/sse to choose FPU... (issue 6962043)

The CL is a reorganization of http://codereview.appspot.com/6549052/

https://codereview.appspot.com/6962043/

thank you. i will try to implement the auto detection part for cmd/dist.

i think you can get it from the cpuid w/ eax=1.

Can you create a global use_sse variable instead of the repeated strcmp
calls? It probably doesn't matter but still...

For detecting SSE2 I think this will work with msvc and gcc (msvc
provides __cpuid automatically):

#include <stdio.h>

#ifndef COMPILER_MSVC
static void
__cpuid(int dst[4], int ax)
{
asm volatile("cpuid"
: "=a" (dst[0]), "=b" (dst[1]), "=c" (dst[2]), "=d" (dst[3])
: "a" (ax));
}
#endif

int
main(void)
{
int info[4];

__cpuid(info, 1);
printf("%#x\n", info[3] & (1<<26));
return 0;
}



https://codereview.appspot.com/6962043/diff/5002/src/cmd/8g/ggen.c
File src/cmd/8g/ggen.c (right):

https://codereview.appspot.com/6962043/diff/5002/src/cmd/8g/ggen.c#newcode868
src/cmd/8g/ggen.c:868: // floating-point. 387 (not SSE2) to
interoperate with 8c
s/ to interoperate with 8c//
that was never true, just a misunderstanding on my part (sse2 and 387
coexist, i was thinking of mmx).

https://codereview.appspot.com/6962043/

ping...

Hello minux.ma@gmail.com, rsc@golang.org (cc:
golang-dev@googlegroups.com),

Please take another look.


https://codereview.appspot.com/6962043/

LGTM

I'd like to autodetect the default GO386 setting but we can do that in a
separate CL.



https://codereview.appspot.com/6962043/diff/5002/src/cmd/8g/ggen.c
File src/cmd/8g/ggen.c (right):

https://codereview.appspot.com/6962043/diff/5002/src/cmd/8g/ggen.c#newcode868
src/cmd/8g/ggen.c:868: // floating-point. 387 (not SSE2) to
interoperate with 8c
still applies

https://codereview.appspot.com/6962043/

https://codereview.appspot.com/6962043/diff/5002/src/cmd/8g/ggen.c
File src/cmd/8g/ggen.c (right):

https://codereview.appspot.com/6962043/diff/5002/src/cmd/8g/ggen.c#newcode868
src/cmd/8g/ggen.c:868: // floating-point. 387 (not SSE2) to
interoperate with 8c
387 coexist,
Done.

https://codereview.appspot.com/6962043/

*** Submitted as
https://code.google.com/p/go/source/detail?r=be005b410410 ***

cmd/dist, cmd/8g: implement GO386=387/sse to choose FPU flavour.

A new environment variable GO386 is introduced to choose between
code generation targeting 387 or SSE2. No auto-detection is
performed and the setting defaults to 387 to preserve previous
behaviour.

The patch is a reorganization of CL6549052 by rsc.

Fixes issue 3912.

R=minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/6962043


https://codereview.appspot.com/6962043/

thanks. i started the autodetect in CL 7035055.