[Bug middle-end/35363] New: Missing bit field coalscing optimization

[xinliangli at gmail dot com]

// David Li

struct A{
  int b1: 3;
  int b2: 3;
  int b3: 2;
  int b4: 17;
}a;
void foo()
{
    a.b1 = 2;
    a.b2 = 3;
    a.b4 = 8;
}

This requires one LOAD + one OR + one STORE, but the generate code looks like:

foo:
.LFB2:
        movzbl  a(%rip), %eax
        andl    $-64, %eax
        orl     $26, %eax
        movb    %al, a(%rip)
        movl    a(%rip), %eax
        andl    $-33554177, %eax
        orb     $8, %ah
        movl    %eax, a(%rip)
        ret


-- 
           Summary: Missing bit field coalscing optimization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35363