[llvm] r280783 - Remove unnecessary call to getAllocatableRegClass

[Justin Bogner via llvm-commits]

Matt Arsenault <arsenm2 at gmail.com> writes:
>> On Oct 28, 2016, at 13:34, Justin Bogner <mail at justinbogner.com> wrote:
>> 
>> Matt Arsenault <arsenm2 at gmail.com <mailto:arsenm2 at gmail.com>> writes:
>>>> On Oct 27, 2016, at 15:39, Justin Bogner <mail at justinbogner.com> wrote:
>>>> 
>>>> Quentin Colombet via llvm-commits <llvm-commits at lists.llvm.org> writes:
>>>>>> On Sep 30, 2016, at 12:07 PM, Krzysztof Parzyszek via llvm-commits
>>>>>> <llvm-commits at lists.llvm.org> wrote:
>>>>>> 
>>>>>> On 9/30/2016 1:46 PM, Justin Bogner via llvm-commits wrote:
>>>>>>> The assert I'm seeing is in the case where `OpRC != nullptr` but
>>>>>>> `ConstrainedRC == nullptr`. Quentin's suggestion would call
>>>>>>> getAllocatableClass(DstRC) in this case, whereas in the committed code
>>>>>>> we just go ahead and do MRI->createVirtualRegister(OpRC). The call to
>>>>>>> createVirtualRegister asserts because OpRC isn't allocatable.
>>>>>> 
>>>>>> This doesn't sound right. This implies that a register was created
>>>>>> for the operand that is not compatible with the operand's
>>>>>> class. Sounds like the problem is somewhere else.
>>>>> 
>>>>> That’s exactly what this code is supposed to fix IIRC. Thus, the
>>>>> current patch does not sound right :).
>>>> 
>>>> Ping. Matt, have you had a chance to look at this?
>>> 
>>> The problem is I want to use the output from constrainRegClass as the
>>> virtual register class instead of getAllocatableClass. Instead of the
>>> assert in the case where constrainRegClass fails, would it work to try
>>> using getAllocatableClass instead? i.e. getAllocatableClass is the
>>> fallback if constrainRegClass fails and then the same create vreg and
>>> copy
>> 
>> Do you mean something like this?
>> 
>> <addregop.patch>
>
> Yes, that works for me. That avoids the original problem of calling it
> right away on the register class in the instruction definition

r285467. Thanks!