[LLVMdev] inline asm semantics: output constraint width smaller than input

[Török Edwin]

On 2009-01-27 23:00, Chris Lattner wrote:
> Right, the interesting wrinkle is that I think llvm's codegen should  
> only see matching constraints of the same type.  If the front-end sees  
> an i8 tied to an i32, it should extend the i8 or do whatever else it  
> needs to do.
>   

My only concern is whether codegen will be able to optimize away extra
extensions/truncations or not?
Consider  an i8 input, and i32 output. If the frontend extends the i8 so
that types match, the codegen should optimize away the extend eventually.
Otherwise we end up with useless extends in the generated assembly.

Best regards,
--Edwin