Re: [PATCH] RISC-V: Note that __builtin_riscv_pause() implies Xgnuzihintpausestate

[Palmer Dabbelt <palmer@rivosinc.com>]

On Mon, 28 Nov 2022 10:45:51 PST (-0800), Palmer Dabbelt wrote:
> On Fri, 18 Nov 2022 09:01:08 PST (-0800), Palmer Dabbelt wrote:
>> On Thu, 17 Nov 2022 22:59:08 PST (-0800), Kito Cheng wrote:
>>> Wait, what's Xgnuzihintpausestate???
>>
>> I just made it up, it's defined right next to the name like those
>> profile extensions are.  I figured that's the most RISC-V way to define
>> something like this, but we could just drop it and run with the
>> definition -- IIRC we just stuck a comment in for Linux and QEMU, I
>> doubt anyone is actually going to implement the "doesn't touch PC"
>> version of pause.
>
> Just checking up on this one.  I don't care a ton about the name, just
> that we document where we're intentionally violating the specs.

I'm just committing this one, no big deal if you want to change the 
wording.  I just want it out of my queue.

>
>>
>>> On Fri, Nov 18, 2022 at 12:30 PM Palmer Dabbelt <palmer@rivosinc.com> wrote:
>>>>
>>>> gcc/ChangeLog:
>>>>
>>>>         * doc/extend.texi (__builtin_riscv_pause): Imply
>>>>         Xgnuzihintpausestate.
>>>> ---
>>>>  gcc/doc/extend.texi | 4 +++-
>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
>>>> index b1dd39e64b8..26f14e61bc8 100644
>>>> --- a/gcc/doc/extend.texi
>>>> +++ b/gcc/doc/extend.texi
>>>> @@ -21103,7 +21103,9 @@ Returns the value that is currently set in the @samp{tp} register.
>>>>  @end deftypefn
>>>>
>>>>  @deftypefn {Built-in Function}  void __builtin_riscv_pause (void)
>>>> -Generates the @code{pause} (hint) machine instruction.
>>>> +Generates the @code{pause} (hint) machine instruction.  This implies the
>>>> +Xgnuzihintpausestate extension, which redefines the @code{pause} instruction to
>>>> +change architectural state.
>>>>  @end deftypefn
>>>>
>>>>  @node RX Built-in Functions
>>>> --
>>>> 2.38.1
>>>>