Bit twiddling builtins

[Falk Hueffner]

Richard Henderson <rth@redhat.com> writes:

> +LIB2FUNCS_3 = _clzsi2 _clzdi2 _ctzsi2 _ctzdi2 _popcount_tab _popcountsi2 \
> +    _popcountdi2 _paritysi2 _paritydi2
> 
> No need for this.  Just add to LIB2FUNCS_2.

Well, the comment above that seemed to imply that some makes or shells
have probems with variables longer than 256 characters, and when I add
them to LIB2FUNCS_2, it does get longer than that. If this is no
longer relevant, we might as well merge LIB2FUNCS_1 and LIB2FUNCS_2...

> +(define_expand "paritydi2"
> +  [(set (match_dup 2)
> +	(popcount:DI (match_operand:DI 1 "register_operand" "")))
> +   (set (match_operand:DI 0 "register_operand" "")
> +	(and:DI (match_dup 2) (const_int 1)))]
> 
> It'd be nice if optabs could synthisize this.  Not a requirement.

I'll look into it.

> +/* Try calculating
> +	(ctz:narrow x)
> +   as
> +	(if_then_else x (ctz:wide (zero_extend:wide x)) (width narrow)).  */
> 
> As I said, these should be undefined at zero.  Ergo CTZ needs
> no special treatment.

OK.

BTW, I'm wondering about these statements in optabs.c when looking for
wider modes:

if (class == MODE_INT || class == MODE_FLOAT || class == MODE_COMPLEX_FLOAT)

Why not MODE_COMPLEX_INT?

-- 
	Falk