llvm dev - Dec 2014 - [LLVMdev] Best way for JIT to query whether llvm.fma.* is fast?

For the Julia language JIT, we'd like be able to tell whether the llvm.fma.*
intrinsic has hardware support.  What's the best way to  query LLVM (JIT)
for this information?

The information would be used in situations where the user wants to use
different algorithms depending on whether FMA hardware is present or not.

- Arch D. Robison

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Does TargetLowering::isFMAFasterThanFMulAndFAdd (
http://llvm.org/docs/doxygen/html/TargetLowering_8h_source.html#l01499)
help?

Jingyue

On Wed, Dec 10, 2014 at 12:48 PM, Robison, Arch <arch.robison at
intel.com>
wrote:
>  For the Julia language JIT, we’d like be able to tell whether the
> llvm.fma.* intrinsic has hardware support.  What’s the best way to  query
> LLVM (JIT) for this information?
>
> The information would be used in situations where the user wants to use
> different algorithms depending on whether FMA hardware is present or not.
>
> - Arch D. Robison
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
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Thanks!  That’s probably close enough for practical purposes.  I looked at the
overrides on various targets, and they all return true if the FMA hardware
exists.

- Arch

From: Jingyue Wu [mailto:jingyue at google.com]
Sent: Wednesday, December 10, 2014 2:56 PM
To: Robison, Arch
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Best way for JIT to query whether llvm.fma.* is fast?

Does TargetLowering::isFMAFasterThanFMulAndFAdd
(http://llvm.org/docs/doxygen/html/TargetLowering_8h_source.html#l01499) help?

Jingyue

On Wed, Dec 10, 2014 at 12:48 PM, Robison, Arch <arch.robison at
intel.com<mailto:arch.robison at intel.com>> wrote:
For the Julia language JIT, we’d like be able to tell whether the llvm.fma.*
intrinsic has hardware support.  What’s the best way to  query LLVM (JIT) for
this information?

The information would be used in situations where the user wants to use
different algorithms depending on whether FMA hardware is present or not.

- Arch D. Robison


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