[Bug middle-end/46935] New: We should recognize expanded switch statement and convert 2 way switch statements into shift & mask test

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46935

           Summary: We should recognize expanded switch statement and
                    convert 2 way switch statements into shift & mask test
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: hubi...@gcc.gnu.org


As observed at http://blog.regehr.org/archives/320 (example 7)
testcase:

int crud (unsigned char c)
{
  return (((((((((((int) c <= 32 || (int) c == 46) || (int) c == 44)
         || (int) c == 58) || (int) c == 59) || (int) c == 60)
          || (int) c == 62) || (int) c == 34) || (int) c == 92)
       || (int) c == 39) != 0);
}

Can be compiled using shift and mask test operation as:
crud:
        movzbl    %dil, %edi
        cmpl      $32, %edi
        jle       ..B1.4
        addl      $-34, %edi
        cmpl      $64, %edi
        jae       ..B1.5
        movl      $1, %eax
        movl      %edi, %ecx
        shlq      %cl, %rax
        movq      $0x400000017001421, %rdx
        testq     %rdx, %rax
        je        ..B1.5
..B1.4:
        movl      $1, %eax
        ret
..B1.5:
        xorl      %eax, %eax
        ret

Probably switch conversion pass could be responsible for this.

Honza