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Re: [Qemu-devel] [V2 PATCH 12/18] softfloat: Fix float64_to_uint32_round


From: Peter Maydell
Subject: Re: [Qemu-devel] [V2 PATCH 12/18] softfloat: Fix float64_to_uint32_round_to_zero
Date: Wed, 11 Dec 2013 19:54:45 +0000

On 11 December 2013 19:16, Tom Musta <address@hidden> wrote:
> The float64_to_uint32_round_to_zero routine is incorrect.
>
> For example, the following test pattern:
>
>     425F81378DC0CD1F / 0x1.f81378dc0cd1fp+38
>
> will erroneously set the inexact flag.
>
> This patch re-implements the routine to temporarily force the
> rounding mode and use the float64_to_uint32 routine.

>  uint32 float64_to_uint32_round_to_zero( float64 a STATUS_PARAM )
>  {
> -    int64_t v;
> +    uint64_t v;
>      uint32 res;
>
> -    v = float64_to_int64_round_to_zero(a STATUS_VAR);
> -    if (v < 0) {
> -        res = 0;
> -        float_raise( float_flag_invalid STATUS_VAR);
> -    } else if (v > 0xffffffff) {
> +    v = float64_to_uint64_round_to_zero(a STATUS_VAR);
> +    if (v > 0xffffffff) {
>          res = 0xffffffff;
> +        STATUS(float_exception_flags) &= ~float_flag_inexact;
>          float_raise( float_flag_invalid STATUS_VAR);
>      } else {
>          res = v;

The patch doesn't seem to be doing what the commit message
says it does?

thanks
-- PMM



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