[Bug c/42968] New: _mm_cvtsi128_si32() should always be assigned to movd.

[herumi at nifty dot com]

_mm_cvtsi128_si32() is an intrinsic function corresponding to movd.
So I think gcc should always generate movd for _mm_cvtsi128_si32().

But gcc with -msse4 option generates pextrd.
So we can't make an application which selects to use SSE4 or not by detecting
cpuid.


For example.
---
% cat t.c
#include <xmmintrin.h>

int main(int argc)
{
    __m128i a = _mm_cvtsi32_si128(argc);
    return _mm_cvtsi128_si32(a);
}

---
% gcc t.c -S -O3 -msse3 && cat t.s
        (snip)
main:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $4, %esp
        movd    8(%ebp), %xmm0
        movd    %xmm0, (%esp)
        movl    (%esp), %eax
        leave
        ret
        (snip)

gcc uses movd.
---
% gcc t.c -S -O3 -msse4 && cat t.s
        (snip)
main:
        pushl   %ebp
        movl    %esp, %ebp
        movd    8(%ebp), %xmm0
        popl    %ebp
        pextrd  $0, %xmm0, %eax
        ret
        (snip)

gcc uses pextrd, which is SSE4.1 mnemonic.
--
Microsoft Visual Studio 2010 beta2.
cl /Ox /FAsc t.c
_main proc
        movd     xmm0, DWORD PTR _argc$[esp-4]
        movd     eax, xmm0
        ret

---
% gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.4.3/configure --enable-__cxa_atexit --enable-shared
--enable-threads=posix --enable-languages=c,c++ --with-arch=i686 --with-ppl
Thread model: posix
gcc version 4.4.3 (GCC)


-- 
           Summary: _mm_cvtsi128_si32() should always be assigned to movd.
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: herumi at nifty dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42968