ref: f080353c96b53a7b881f470d8e8f6e1151fa6524 dir: /builtins.arm64.s/
TEXT __builtin_ctz(SB),1,$0 RBITW R0, R0 CLZW R0, R0 RETURN TEXT __builtin_clz(SB),1,$0 CLZW R0, R0 RETURN TEXT __builtin_clzll(SB),1,$0 CLZ R0, R0 RETURN