Codegen for some bitflag checks could be optimized #13743

More info: dotnet/coreclr#27603 (comment)

Sample code:

public static bool HasHighBitSet(uint value) {
    return (value & 0x8000_0000) != 0;
}

Actual codegen:

    L0000: test ecx, 0x80000000
    L0006: setnz al
    L0009: movzx eax, al
    L000c: ret

Replacing the first two instructions with test ecx, ecx and setl al would save 4 bytes of codegen. It's a minor savings but might help if this pattern occurs within a hot loop.

category:cq
theme:basic-cq
skill-level:intermediate
cost:small