[LLVMdev] Type Legalizer Question.

[Chris Lattner]

On Oct 2, 2008, at 8:38 AM, Eli Friedman wrote:

> On Thu, Oct 2, 2008 at 7:34 AM, Evan Cheng <evan.cheng at apple.com>  
> wrote:
>>
>> On Oct 2, 2008, at 2:01 AM, sanjiv gupta wrote:
>>
>>>
>>>>
>>>> So you have a i16 register class which makes the type legal. You  
>>>> can
>>>> make loads and stores legal (can you?). But you will have to custom
>>>> lower all other i16 operations. This will work, but it requires a  
>>>> lot
>>>> of target specific code.
>>>
>>> True. If we add the i16 reg class we will need to write a lot of
>>> target specific code.
>>> To avoid that our idea was not to tell the legalizer about the i16
>>> regclass and let it expand everything but ignore the pointers.
>>
>> You can try just marking all i16 operations, other than load and
>> store, as "expand". Would that work?
>
> Won't work; LLVM expects at least some basic operations, like add, to
> be legal in legal register types.

That sounds like a bug, not a feature.

-Chris