[Bug tree-optimization/43692] New: small loop not vectorized

[wbrana at gmail dot com]

This loop isn't vectorized:

float a[4], b[4], c[4];
int main () {
  int i;

  for (i=0; i<4; i++){
    a[i] = b[i] + c[i];
  }
}
main:
.LFB0:
        .cfi_startproc
        movss   b(%rip), %xmm0
        addss   c(%rip), %xmm0
        movss   %xmm0, a(%rip)
        movss   b+4(%rip), %xmm0
        addss   c+4(%rip), %xmm0
        movss   %xmm0, a+4(%rip)
        movss   b+8(%rip), %xmm0
        addss   c+8(%rip), %xmm0
        movss   %xmm0, a+8(%rip)
        movss   b+12(%rip), %xmm0
        addss   c+12(%rip), %xmm0
        movss   %xmm0, a+12(%rip)
        ret
        .cfi_endproc

but this loop is vectorized:

float a[8], b[8], c[8];
int main () {
  int i;

  for (i=0; i<8; i++){
    a[i] = b[i] + c[i];
  }
}

main:
.LFB0:
        .cfi_startproc
        movaps  b(%rip), %xmm0
        addps   c(%rip), %xmm0
        movaps  %xmm0, a(%rip)
        movaps  b+16(%rip), %xmm0
        addps   c+16(%rip), %xmm0
        movaps  %xmm0, a+16(%rip)
        ret
        .cfi_endproc


-- 
           Summary: small loop not vectorized
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: wbrana at gmail dot com
  GCC host triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43692