Re: [PATCH][C/C++] Do not promote return arguments

[Paolo Bonzini <bonzini at gnu dot org>]

> I did some investigation and i386 consistently does not set
> TARGET_PROMOTE_FUNCTION_RETURN (that is, it returns QImode for
> char return types from function_value).

That seems wrong.

> Now that we end up
> with zero-extension instead of letting the upper bits undefined
> is due to the *mov[qh]i_1 insns which have
>
> (define_insn "*movqi_1"
>   [(set (match_operand:QI 0 "nonimmediate_operand" "=q,q ,q ,r,r ,?r,m")
>         (match_operand:QI 1 "general_operand"      " 
> q,qn,qm,q,rn,qm,qn"))]
>   "!(MEM_P (operands[0]) && MEM_P (operands[1]))"
> {
>   switch (get_attr_type (insn))
>     {
>     case TYPE_IMOVX:
>       gcc_assert (ANY_QI_REG_P (operands[1]) || MEM_P (operands[1]));
>       return "movz{bl|x}\t{%1, %k0|%k0, %1}";
>
> seemingly because of partial reg stalls (is this still true?).

Yes.

Paolo