[Bug tree-optimization/89184] New: GCC does not simplify expressions involving shifts, bitwise operators and comparisons.

[m...@nieper-wisskirchen.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89184

            Bug ID: 89184
           Summary: GCC does not simplify expressions involving shifts,
                    bitwise operators and comparisons.
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: m...@nieper-wisskirchen.de
  Target Milestone: ---

GCC compiles the function

int foo (unsigned i)
{
    return ((i >> 1) & 3) == 2;
}

to (in x86-64 assembly)

foo:
        shrl    %edi
        xorl    %eax, %eax
        andl    $3, %edi
        cmpl    $2, %edi
        sete    %al
        ret

This is more complicated than necessary; the following assembly produced by
clang needs one instruction less:

foo:
        andl    $6, %edi
        xorl    %eax, %eax
        cmpl    $4, %edi
        sete    %al
        retq