[Bug target/47825] SSE bitwise operations on floats work -g, fail -O3

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47825

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-*-*
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2011.02.21 10:40:58
                 CC|                            |hjl at gcc dot gnu.org
          Component|c                           |target
         Resolution|INVALID                     |
     Ever Confirmed|0                           |1

--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-02-21 10:40:58 UTC ---
The issue is that maskarray is initialized as array of ints but then you
load it as array of floats, the scheduler re-orders those so you see
a load from uninitialized stack:

test_setelement:
.LFB546:
        subq    $40, %rsp
.LCFI0:
        movaps  16(%rsp), %xmm0
        movl    $0, 16(%rsp)
        movl    $0, 20(%rsp)
        movaps  %xmm0, %xmm1
        andnps  .LC1(%rip), %xmm0
        movl    $0, 24(%rsp)
        movl    $-1, 28(%rsp)
...

what is a bit inconsistent is that for mm_load_pd we use a type that
allows aliasing:

/* The Intel API is flexible enough that we must allow aliasing with other
   vector types, and their scalar components.  */
typedef long long __m128i __attribute__ ((__vector_size__ (16),
__may_alias__));
typedef double __m128d __attribute__ ((__vector_size__ (16), __may_alias__));

...

/* Load two DPFP values from P.  The address must be 16-byte aligned.  */
extern __inline __m128d __attribute__((__gnu_inline__, __always_inline__,
__artificial__))
_mm_load_pd (double const *__P)
{
  return *(__m128d *)__P;
}

but for mm_load_ps we don't:

/* Internal data types for implementing the intrinsics.  */
typedef float __v4sf __attribute__ ((__vector_size__ (16)));

...

/* Load four SPFP values from P.  The address must be 16-byte aligned.  */
extern __inline __m128 __attribute__((__gnu_inline__, __always_inline__,
__artificial__))
_mm_load_ps (float const *__P)
{
  return (__m128) *(__v4sf *)__P;
}


re-opening to investigate that.  HJ, are the SSE1 intrinsics not
aliasing in the Intel API?  The above snippets are from trunk.