[LLVMdev] type legalization/operation action

[kewuzhang]

On Feb 5, 2015, at 5:41 PM, Tom Stellard <tom at stellard.net> wrote:

> 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.
> 

yeah., it is working.
>> 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.

——————how to understand the “promote” in CallingConv.td?

>> 
>> (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.
thank you very much!

 Think I run into this problem as well,  it made me think the  Promote is not working.

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