[Bug tree-optimization/56118] New: No constant propagation in vector field assignment

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56118



             Bug #: 56118

           Summary: No constant propagation in vector field assignment

    Classification: Unclassified

           Product: gcc

           Version: 4.8.0

            Status: UNCONFIRMED

          Keywords: missed-optimization

          Severity: normal

          Priority: P3

         Component: tree-optimization

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: gli...@gcc.gnu.org

            Target: x86_64-linux-gnu





Hello,



with this code:



#include <x86intrin.h>

__m128d f(){

  __m128d r={3,4};

  r[0]=1;

  r[1]=2;

  return r;

}



gcc sees the following and fails to optimize it:



  r = { 3.0e+0, 4.0e+0 };

  BIT_FIELD_REF <r, 64, 0> = 1.0e+0;

  BIT_FIELD_REF <r, 64, 64> = 2.0e+0;



Nothing fixes it at the RTL level either, so we end up with:



    movapd    .LC0(%rip), %xmm0

    movlpd    .LC1(%rip), %xmm0

    movhpd    .LC2(%rip), %xmm0