Re: [Qemu-devel] [PATCH] target-i386: Fix regression with maxsd SSE2 instruction

[Laurent Desnogues]

On Tue, Nov 8, 2011 at 2:00 PM, Jason Wessel <address@hidden> wrote:
> The maxsd instruction needs to take into account the sign of the
> numbers 64 bit numbers.  This is a regression that was introduced in
> 347ac8e356 (target-i386: switch to softfloat).
>
> The case that fails is:
>
> maxsd  %xmm1,%xmm0
>
> When xmm1 = 24 and xmm0 = -100
>
> This was found running the glib2 binding tests where it prints the message:
> /binding/transform:
> GLib-GObject-WARNING **: value "24.000000" of type `gdouble' is invalid or 
> out of range for property `value' of type `gdouble'
> aborting...
>
> Using a signed comparison fixes the problem.
>
> Signed-off-by: Jason Wessel <address@hidden>
> ---
>  target-i386/ops_sse.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/target-i386/ops_sse.h b/target-i386/ops_sse.h
> index aa41d25..bcc0ed9 100644
> --- a/target-i386/ops_sse.h
> +++ b/target-i386/ops_sse.h
> @@ -584,8 +584,8 @@ void helper_ ## name ## sd (Reg *d, Reg *s)\
>  #define FPU_SUB(size, a, b) float ## size ## _sub(a, b, &env->sse_status)
>  #define FPU_MUL(size, a, b) float ## size ## _mul(a, b, &env->sse_status)
>  #define FPU_DIV(size, a, b) float ## size ## _div(a, b, &env->sse_status)
> -#define FPU_MIN(size, a, b) (a) < (b) ? (a) : (b)
> -#define FPU_MAX(size, a, b) (a) > (b) ? (a) : (b)

Isn't maxsd a floating-point instruction?  If so, shouldn't
FPU_{MIN,MAX} use softfloat operations?


Laurent

> +#define FPU_MIN(size, a, b) (int ## size ## _t)(a) < (int ## size ## _t)(b) 
> ? (a) : (b)
> +#define FPU_MAX(size, a, b) (int ## size ## _t)(a) > (int ## size ## _t)(b) 
> ? (a) : (b)
>  #define FPU_SQRT(size, a, b) float ## size ## _sqrt(b, &env->sse_status)
>
>  SSE_HELPER_S(add, FPU_ADD)
> --
> 1.7.1
>
>
>