Include SSE state in i386 fenv_t (bug 16064)

[H.J. Lu]

On Fri, May 9, 2014 at 5:17 AM, Joseph S. Myers <joseph@codesourcery.com> wrote:
> On Thu, 8 May 2014, H.J. Lu wrote:
>
>> > @@ -63,7 +66,7 @@ __fesetenv (const fenv_t *envp)
>> >                               & (FE_ALL_EXCEPT | FE_TOWARDZERO));
>> >        temp.__status_word &= ~FE_ALL_EXCEPT;
>> >        temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT;
>> > -      temp.__eip = envp->__eip;
>> > +      temp.__eip = 0;
>> >        temp.__cs_selector = envp->__cs_selector;
>> >        temp.__opcode = envp->__opcode;
>>
>> Should we also set __cs_selector/__opcode/__data_offset/__data_selector
>> to 0?
>
> Not as part of this patch (the change there was simply to avoid setting
> __eip to a value that now represents MXCSR and so is completely logically
> unrelated to __eip).
>
> I don't think any of those fields you list are particularly meaningfully
> part of the C floating-point environment, so they could reasonably all be
> set to 0 - but any such change should be done in sync for the i386 and
> x86_64 implementations.  The point of this patch is to fix an actual bug,
> visible to ordinary C code, arising from a case where the i386
> implementation misses functionality present in the x86_64 version.
>

There are 4 unused short int fields in fenv_t.  Can we use 2 of them
for mxcsr instead of re-using __eip?

-- 
H.J.