[LLVMdev] half to float intrinsic promotion

[kewuzhang]

Thank  you very much!
don’t know why I just overlooked the llvm_half_ty when I was reading the intrinsics.td

best

kevin
On Feb 12, 2015, at 1:31 PM, Ahmed Bougacha <ahmed.bougacha at gmail.com> wrote:

> On Thu, Feb 12, 2015 at 8:48 AM, kewuzhang <kewu.zhang at amd.com> wrote:
>> 
>> Hi Guys,
>> 
>> I am trying to promote half to float for my intrinsic math operations,
>> following class and pattern  are defined.
>> 
>> "
>> class  S_HF__HF< string asmstr> : Intrinsic
>>        <[llvm_float_ty  ],  [llvm_float_ty  ],
>> [IntrNoMem],
>> !strconcat(asmstr,    "_f16")>;
>> 
>> def :Pat<( f16 (int_my_math_f16 f16:$src)), (F2Hsr (FEXTsr f16:$src) )>;
>> 
>> 
>> “
>> where FEXTsr is implementing the fextend type profile,   F2Hsr is
>> implementing as the  float to half conversion .
>> “int_my_math_f16”  is implementing the “S_HF__HF” profile above.
>> I am just trying to
>> (1) convert the $src from f16 to f32 using FEXTsr.
>> (2) use the F2Hsr to convert the f32 back to f16.
>> for testing.
>> however, I always got the error
>> ”
>> Type inference contradiction found, merging 'f32' into 'f16'
>> def :Pat<( f16 (int_my_math_f16 f16:$src)), (F_2_F16sr (FEXTsr f16:$src) )>;
>> 
>> “
>> 
>> 
>> Wondering what is the reason? I noticed that LLVM does not have the
>> intrinsic type “LLVM_f16_ty”, so I always use “LLVM_float_ty” for it as long
>> as it is a float or half.
> 
> Hi Kevin,
> 
> In "llvm_float_ty", "float" means f32 (as in the IR language
> reference, and as defined in include/llvm/IR/Intrinsics.td).  So in
> your example, TableGen complains because you're feeding an f16 to an
> intrinsic declared as taking an f32.
> 
> However, there's also "llvm_half_ty" in Intrinsics.td, corresponding
> to f16; why not use that instead?
> 
> -Ahmed
> 
>> best
>> 
>> Kevin
>> 
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