> Am 11.04.2024 um 16:03 schrieb Segher Boessenkool
> <seg...@kernel.crashing.org>:
>
> On Wed, Apr 10, 2024 at 08:32:39PM +0200, Uros Bizjak wrote:
>>> On Wed, Apr 10, 2024 at 7:56 PM Segher Boessenkool
>>> <seg...@kernel.crashing.org> wrote:
>>> This is never okay. You cannot commit a patch without approval, *ever*.
>
> This is the biggest issue, to start with. It is fundamental.
I have approved the patch as you might have noticed.
Richard
>>> That patch is also obvious -- obviously *wrong*, that is. There are
>>> big assumptions everywhere in the compiler how a CC reg can be used.
>>> This violates that, as explained elsewhere.
>>
>> Can you please elaborate what is wrong with this concrete patch.
>
> The explanation of the patch is contradictory to how RTL works at all,
> so it is just wrong. It might even do something sane, but I didn't get
> that far at all!
>
> Write good email explanations, and a good proposed commit message.
> Please. It is the only one people can judge a patch. Well, apart
> from doing everything myself from first principles, ignoring everything
> you said, just looking at the patch itself, but that is a hundred times
> more work. I don't do that.
>
>> The
>> part that the patch touches has several wrong assumptions, and the
>> fixed "???" comment just emphasizes that. I don't see what is wrong
>> with:
>>
>> (define_insn "@pushfl<mode>2"
>> [(set (match_operand:W 0 "push_operand" "=<")
>> (unspec:W [(match_operand 1 "flags_reg_operand")]
>> UNSPEC_PUSHFL))]
>> "GET_MODE_CLASS (GET_MODE (operands[1])) == MODE_CC"
>> "pushf{<imodesuffix>}"
>> [(set_attr "type" "push")
>> (set_attr "mode" "<MODE>")])
>
> What does it even mean? What is a flags:CC? You always always always
> need to say what is *in* the flags, if you want to use it as input
> (which is what unspec does). CC is weird like this. Most targets do
> not have distinct physical flags for every condition, only a few
> conditions are "alive" at any point in the program!
>
>> it is just a push of the flags reg to the stack. If the push can't be
>> described in this way, then it is the middle end at fault, we can't
>> just change modes at will.
>
> But that is not what this describes: it operates on the flags register
> in some unspecified way, and pushes the result of *that* to the stack.
>
> (Stack pointer modification is not described here btw, should it be? Is
> that magically implemented by the backend some way, via type=push
> perhaps?)
>
>
> Segher
