Re: [PATCH] rs6000: Fix issue in specifying PTImode as an attribute [PR106895]

[Peter Bergner <bergner@linux.ibm.com>]

On 3/18/24 9:36 AM, Segher Boessenkool wrote:
> Hi!
> 
> On Fri, Feb 23, 2024 at 03:04:13PM +0530, jeevitha wrote:
>> PTImode attribute assists in generating even/odd register pairs on 128 bits.
> 
> It is a mode, not an attribute.  Attributes are on declarations, while
> modes are on a much more fundamental level (every value has a mode, in
> GCC!)
> 
>> When the user specifies PTImode as an attribute, it breaks because there is no
>> internal type to handle this mode . We have created a tree node with dummy type
>> to handle PTImode.
> 
> You are talking about the mode attribute.  Aha.

Correct.



>> We are not documenting this dummy type since users are not
>> allowed to use this type externally.
> 
> Not sure what this is meant to mean?  What does "allowed to" mean, even?
> We do not forbid people from doing anything (we can discourage them
> though).  Or dso you mean something just doesn't work?

The use case is the Linux kernel will use the mode attribute as shown in
the test case.  The type she created was needed for the code to "work"
internally, but we don't want to advertise it to users, so that's why we're
not documenting it.  Yes, pesky users who go digging through the GCC source
could find it and use it, but we don't want to encourage them. :-)


>> 	PR target/106895
>> 	* config/rs6000/rs6000.h (enum rs6000_builtin_type_index): Add fields
>> 	to hold PTImode type.
> 
> An enum does not have fields.  What do you actually mean?

Yeah, as per your follow-on comment, I think a simple "Add RS6000_BTI_INTPTI."
should suffice.


Peter