[Bug target/94393] New: Powerpc suboptimal 64-bit constant comparison

[npiggin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94393

            Bug ID: 94393
           Summary: Powerpc suboptimal 64-bit constant comparison
           Product: gcc
           Version: 9.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: npiggin at gmail dot com
  Target Milestone: ---

--- test case ----
void test1(unsigned long a)
{ 
        if (a > 0xc000000000000000ULL)
                printf("yes\n");
}
void test2(unsigned long a)
{
        if (a >= 0xc000000000000000ULL)
                printf("yes\n");
}
------------------

The first (important part) compiles to

        li 9,-1
        rldicr 9,9,0,1
        cmpld 0,3,9
        blelr 0

The second to

        lis 9,0xbfff
        ori 9,9,0xffff
        sldi 9,9,32
        oris 9,9,0xffff
        ori 9,9,0xffff
        cmpld 0,3,9
        blelr 0

The second could use the same 2-insn constant as the first, but with bltlr.