[llvm-dev] using experimental intrinsics failed

[Craig Topper via llvm-dev]

I just pasted that code and ran it through llc, opt, and llvm-as. All
passed without issue. What version of llvm are you using?

~Craig


On Thu, Sep 3, 2020 at 5:53 PM Xuan Tang <xt585 at nyu.edu> wrote:

> Hi Craig:
>
> I tried that, now the function is like this:
> *; Function Attrs: norecurse nounwind readnone ssp uwtable*
> *define* { *double*, *double* } *@add*(*double*, *double*, *double*,
> *double*) local_unnamed_addr #0 {
>   *%5* = *call* *double* *@llvm.experimental.constrained.fadd*(*double*
> *%0*, *double* *%2*, *metadata* !"round.downward", *metadata* !"fpexcept.i
> gnore")
>   *%6* = *fadd* *double* *%1*, *%3*
>   *%7* = *insertvalue* { *double*, *double* } undef, *double* *%5*, 0
>   *%8* = *insertvalue* { *double*, *double* } *%7*, *double* *%6*, 1
>   *ret* { *double*, *double* } *%8*
> }
>
> *declare* *double* *@llvm.experimental.constrained.fadd*(*double*,
> *double*, *metadata*, *metadata*)
>
> But now I get the error at the line of declaration:
> error: expected function name
>
> I tried the example at
> https://llvm.org/docs/LangRef.html#variable-argument-handling-intrinsics and
> that compiles fine, which means the declaration code should work as well.
>
> Thank you
> Xuan Tang
> On Sep 3, 2020, 19:41 -0500, Craig Topper <craig.topper at gmail.com>, wrote:
>
> I think you need a declaration like this at module scope in your IR file.
> Everything that's called either needs to be defined or declared even if it
> is an intrinsic. It doesn't matter if the declaration is before or after
> the use.
>
> *declare double* *@llvm.experimental.constrained.fadd*(*double,* *double*
> , *metadata*", *metadata*)
>
> ~Craig
>
>
> On Thu, Sep 3, 2020 at 5:36 PM Xuan Tang via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi:
>>
>> Sorry I need to send email directly. I am new to llvm and trying to write
>> interval arithmetic, which requires changing rounding mode during
>> computation.
>>
>> The document I found
>> https://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics
>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_docs_LangRef.html-23constrained-2Dfloating-2Dpoint-2Dintrinsics&d=DwMFaQ&c=slrrB7dE8n7gBJbeO0g-IQ&r=hLa09n1yvyXy9ubp1REixw&m=dfQEfUhbjIQmr4ORw7fkG8wv0VKl4Rf0QVcMJwAmQGA&s=7N7tSGQ2qieHYkFTYdM5hRvGW564X0nUZFD4S75z_Vs&e=>,
>> seems to be doing the trick. Here is the piece of code that I did:
>>
>> *%5* = *call* *double* *@llvm.experimental.constrained.fadd*(*double*
>> *%0*, *double* *%2*, *metadata* !"round.downward", *metadata* !"fpexcept
>> .ignore")
>>
>> It is taking the first and third argument and adding them together with
>> the downward rounding mode. However, when I try to convert it to bit code,
>> I got the error:
>>
>> error: use of undefined value '@llvm.experimental.constrained.fadd'
>>
>> Is there any flags I need to add in order to use this intrinsic? Or this
>> is just a wrong function call. I am using the llvm version 10.0.1.
>>
>> Thank you
>> Xuan Tang
>> _______________________________________________
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>> llvm-dev at lists.llvm.org
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>>
>
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