~llvm.fsh[rl] patterns not recognized

[Validark]

Zig Godbolt
LLVM Godbolt

Example 1:

export fn rotate(x: u64, y: u64) u64 {
    return x >> @truncate(~y) | x << @truncate(y + 1);
}

Should be:

rotate:
        lea     ecx, [rsi + 1]
        mov     rax, rdi
        rol     rax, cl
        ret

Example 2:

export fn rotate2(x: u64, y: u64) u64 {
    return x >> @truncate(y + 1) | x << @truncate(~y);
}

Should be:

rotate2:
        lea     ecx, [rsi + 1]
        mov     rax, rdi
        ror     rax, cl
        ret

Might not be useful in most situations, but these are also valid transformations:

rotate:
        mov     rcx, rsi
        not     cl
        mov     rax, rdi
        ror     rax, cl
        ret

rotate2:
        mov     rcx, rsi
        not     cl
        mov     rax, rdi
        rol     rax, cl
        ret