[Bug tree-optimization/63568] New: Missed optimization (a & ~mask) | (b & mask) = a ^ ((a ^ b) & mask)

[olegendo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63568

            Bug ID: 63568
           Summary: Missed optimization (a & ~mask) | (b & mask) = a ^ ((a
                    ^ b) & mask)
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: olegendo at gcc dot gnu.org
            Target: sh*-*-*

As of 216350, compiling the following example on SH with -O2

unsigned int test (unsigned int a, unsigned int b, unsigned int m)
{
  return (a & ~m) | (b & m);
}

results in:
        not     r6,r0
        and     r0,r4
        and     r6,r5
        mov     r4,r0
        rts
        or      r5,r0

A shorter way is to do the same is:
        xor     r4,r5
        and     r5,r6
        mov     r6,r0
        rts
        xor     r4,r0

If this kind of stuff is done as part of tree optimization, then this is
probably not SH specific, although I haven't checked with other targets.