[llvm-dev] mapping calls to exp() to expf opcode

[Phil Tomson via llvm-dev]

Both of them have 'Legal' (as well as sin and cos), but that doesn't make
any difference - I still don't see exp, exp2, sin or cos show up as opcodes
in the assembly. For some reason calls to sqrt show up as opcodes (sqrtf) -
I'm puzzled as to what is different with sqrt.

Phil



On Thu, Sep 1, 2016 at 10:44 AM, Ryan Taylor <ryta1203 at gmail.com> wrote:

> Phil,
>
>   Are you seeing the fexp2 SDNode with -view-legalize-dags and then a call
> with -view-dag-combine2-dags?
>
>   In XXXISelLowering.cpp please try to explicitly make fexp2 'legal', ie
> "setOperationAction(ISD::FEXP2, MVT::f32, Legal);
> setOperationAction(ISD::FEXP2, MVT::f64, Legal)". This worked for me, I am
> now no longer getting a call and am now getting an ISEL error (not matching
> SDNode in tablegen, which is what you want since it's legal on your target).
>
>   I find this confusing since the default is suppose to be 'Legal' from my
> understanding but LLVM is not always consistent this way, the community has
> decided to do things 'this way' or 'that way' depending on 'what's common'
> sometimes.
>
> Thanks,
>
> -Ryan
>
> On Wed, Aug 31, 2016 at 6:40 PM, Phil Tomson via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> We've got both an sqrtf and an expf opcode in our architecture. If I call
>> sqrt() on the C side, I see the sqrtf opcode show up in the generated
>> assembly. However, if I call exp() on the C side, I don't see the expf
>> opcode show up on the generated assembly, I see a call to an exp function
>> from libm.
>>
>> Here's what we've got in our TargetInstrinfo.td file for both of these
>> instructions:
>> def SQRTF64 : Other2ROp< 0b0001101, "sqrtF", fsqrt, OpInfo_F64, II_ELEMF3
>> >;
>> def SQRTF32 : Other2ROp< 0b0001101, "sqrtF", fsqrt, OpInfo_F32, II_ELEMF1
>> >;
>>
>> def EXPF64 :   Other2ROp< 0b0001010, "expF", fexp2, OpInfo_F64, II_ELEMF3
>> >;
>> def EXPF32 :   Other2ROp< 0b0001010, "expF", fexp2, OpInfo_F32, II_ELEMF1
>> >;
>>
>>
>> ..essentially the same kind of definition for both SQRTF and EXPF, but
>> for the latter I don't see expf opcodes being generated.
>>
>> Any idea what might be missing for exp?
>>
>> Phil
>>
>> _______________________________________________
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>> llvm-dev at lists.llvm.org
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>>
>>
>
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