[LLVMdev] type legalization/operation action

[Tom Stellard]

On Thu, Feb 05, 2015 at 04:56:25PM -0500, kewuzhang wrote:
> Dear there, 
> 
> I have a target which is supporting the  32 bit operations natively. Right now,I want to make it support the 16 bits operations as well.

If you want to make 16-bit types legal you need to call:

addRegisterClass(MVT::i16, SomeRegisterClass) in your Target's TargetLowering
implementation.

> My initial thought is:
> (1) 
> I can adding something like “ CCIfType< [i16], CCPromoteToType<i32>>”, to the CallingConv.td, then “all” the 16 bits operands will be automatically promoted to 32 bits, it will be all set.
> but looks it is not the case.
> 
> (2) 
> Then I tried adding something like “ setOperationAction(ISD::ADD,  MVT::i16, Promote)” to the IselLowering,  it still failed to  select the (i16 + i16)..
> 

Promoting ISD::ADD is not supported.  Take a look in SelectionDAGLegalize::PromoteNode()
to see which opcodes can be promoted.  You will either need to custome lower it or
properly handle it in the PromoteNode() function.

-Tom

> wondering which part I missed?
> 
> best
> 
> Kevin
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