code review 3469044: runtime/linux/386: set FPU to 64-bit precision

runtime/linux/386: set FPU to 64-bit precision

Fixes issue 550.

[rsc, 2010-12-10 20:44:28]

Hello r (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[r, 2010-12-10 20:57:08]

i don't find the comment clear at all.  for instance, what mode are you setting?

On 12/10/10, rsc@golang.org <rsc@golang.org> wrote:
> Reviewers: r,
>
> Message:
> Hello r (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change.
>
>
> Description:
> runtime/linux/386: set FPU to 64-bit precision
>
> Fixes issue 550.
>
> Please review this at http://codereview.appspot.com/3469044/
>
> Affected files:
>    M src/pkg/runtime/linux/386/rt0.s
>
>
> Index: src/pkg/runtime/linux/386/rt0.s
> ===================================================================
> --- a/src/pkg/runtime/linux/386/rt0.s
> +++ b/src/pkg/runtime/linux/386/rt0.s
> @@ -5,5 +5,14 @@
>   // Darwin and Linux use the same linkage to main
>
>   TEXT _rt0_386_linux(SB),7,$0
> +	// Linux starts the FPU in 80-bit mode.
> +	// Convention in Go is 64-bit mode.
> +	// Except for x87 bugs, this makes float64
> +	// math more like it is on other operating systems
> +	// and architectures.
> +	PUSHL $0x27F
> +	FLDCW	0(SP)
> +	POPL AX
> +
>   	JMP	_rt0_386(SB)
>
>
>
>

[rsc, 2010-12-10 21:02:11]

Hello r (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2010-12-10 22:26:55]

LGTM
much better

[rsc, 2010-12-13 15:04:57]

*** Submitted as fc030afcda3c ***

runtime/linux/386: set FPU to 64-bit precision

Fixes issue 550.

R=r
CC=golang-dev
http://codereview.appspot.com/3469044