[Bug target/54685] New: [SH] Improve unsigned int comparison with 0x7FFFFFFF

["olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54685

             Bug #: 54685
           Summary: [SH] Improve unsigned int comparison with 0x7FFFFFFF
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: olegendo@gcc.gnu.org
        ReportedBy: olegendo@gcc.gnu.org
            Target: sh*-*-*


The following cases:


int test_00 (unsigned int a)
{
  return !(a > 0x7FFFFFFF);
}


int test_01 (unsigned int a)
{
  return a <= 0x7FFFFFFF;
}

int test_02 (unsigned int a)
{
  return a < 0x80000000;
}

compile to (-m4 -O2):
        not     r4,r0
        shll    r0
        rts
        movt    r0

which would be better as:
        cmp/pz    r4    ! T = r4 >= 0 (signed)
        rts
        movt    r0


For some reason, these do not go through the cstoresi4 expander, but the
following does:

int test (unsigned int a)
{
  return a > 0;
}

The cstore is expanded by the middle-end into something like

(insn 6 3 7 2 (set (reg:SI 167)
        (not:SI (reg/v:SI 164 [ a ]))) sh_tmp.cpp:1984 185 {one_cmplsi2}
     (nil))
(insn 7 6 8 2 (parallel [
            (set (reg:SI 166 [ D.42391+-3 ])
                (lshiftrt:SI (reg:SI 167)
                    (const_int 31 [0x1f])))
            (clobber (reg:SI 147 t))
        ]) sh_tmp.cpp:1984 167 {lshrsi3_n_clobbers_t}
     (nil))


And combine then looks for:

Failed to match this instruction:
(parallel [
        (set (reg:SI 166 [ D.42391+-3 ])
            (ge:SI (reg:SI 4 r4 [ a ])
                (const_int 0 [0])))
        (clobber (reg:SI 147 t))
    ])