[Bug target/53907] New: gcc uses unaligned load when aligned load was requested

["neleai at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53907

             Bug #: 53907
           Summary: gcc  uses unaligned load when aligned load was
                    requested
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: neleai@seznam.cz


A gcc 4.7 and 4.8 emit movdqu instead movdqa for aligned load instrinc.

#include <emmintrin.h>
__m128i x(char *s){
  __m128i sz,z,mvec;
  s-=((unsigned long) s)%16;
  sz=_mm_load_si128(s);
  return sz;
}

Output of gcc -O3 -S follows

  .file "int.c"
  .text
  .p2align 4,,15
  .globl  x
  .type x, @function
x:
.LFB517:
  .cfi_startproc
  movq  %rdi, %rax
  andl  $15, %eax
  negq  %rax
  movdqu  (%rdi,%rax), %xmm0
  ret
  .cfi_endproc
.LFE517:
  .size x, .-x
  .ident  "GCC: (Debian 20120704-1) 4.8.0 20120704 (experimental) [trunk
revision 189247]"
  .section  .note.GNU-stack,"",@progbits