[Bug target/82680] New: Use cmpXXss and cmpXXsd for setcc boolean compare

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82680

            Bug ID: 82680
           Summary: Use cmpXXss and cmpXXsd for setcc boolean compare
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ubizjak at gmail dot com
  Target Milestone: ---

Both, ICC and clang use cmpXXss and cmpXXsd instructions for setcc boolean
compare:

int g(double x, double y)
{
        return x == y;
}

ICC:
        cmpeqsd   %xmm1, %xmm0
        movd      %xmm0, %eax
        negl      %eax
        ret

clang:
        cmpeqsd %xmm1, %xmm0
        movq    %xmm0, %rax
        andl    $1, %eax
        retq

gcc w/ -ffast-math:

        xorl    %eax, %eax
        comisd  %xmm1, %xmm0
        sete    %al
        ret

Versions with direct moves avoid partial register stalls.