[llvm-dev] EuroLLVM Numerics issues

Kevin Neal via llvm-dev llvm-dev at lists.llvm.org
Thu Apr 11 12:15:01 PDT 2019

I’m working on fneg. I started with the IRBuilder and found that some of the transformation passes use it. Updating the m_FNeg() matchers gets me farther, but the InstCombiner doesn’t know how to deal with a non-BinaryOperator.

Sorry for the delay in responding to this thread, but I’ve been out of the country and am a little behind on email.

Kevin P. Neal
SAS/C and SAS/C++ Compiler
Host Research and Development
SAS Institute, Inc.

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Arsenault, Matthew via llvm-dev
Sent: Friday, March 29, 2019 5:52 PM
To: Michael Berg <michael_c_berg at apple.com>; llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] EuroLLVM Numerics issues

A few things I’ve been thinking about:

  *   Is anyone working on finishing the migration to using the new fneg instruction?
  *   Controls for allowing and/or mandating denormal flushing

     *   Making denormal-fp-math attribute per FP type
     *   FTZ flag

  *   Dealing with constrained and unconstrained versions of target FP intrinsics
  *   Can we define a policy or general direction for snan handling?

     *   Relatedly, llvm.minnum/llvm.maxnum should be renamed to fmin/fmax, and a new set of minnum/maxnum that follow the defined snan behavior are needed. This would give 3 complete sets of min/max intrinsics
     *   Are target features/attributes allowed to change the behavior of standard operations/intrinsics?

  *   Adding FP min/max to atomicrmw, and which versions are needed

From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces at lists.llvm.org>> on behalf of llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
Reply-To: Michael Berg <michael_c_berg at apple.com<mailto:michael_c_berg at apple.com>>
Date: Friday, March 29, 2019 at 1:05 PM
To: llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
Subject: [llvm-dev] EuroLLVM Numerics issues

All:  There will be a BoF talk at the EuroLLVM conference regarding Numerics (FMF and module flags which control fp behavior and optimization).

Even if you are not going to be in attendance, please reply to this thread as we are collecting open issues and ideas for future direction in all layers of LLVM for which optimizations are controlled by numerics flags. Please read over the numerics blog if you like for reference material:


p.s. (restarting this thread here).

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