Awesome work Geoff! I look forward to looking at this / playing with it soon!
:) On Mon, Sep 16, 2013 at 3:16 PM, Geoffrey Mainland <mainl...@apeiron.net>wrote: > The SIMD branch, available as wip/simd, is ready for review/merge. It > could use some review---Simon and Simon, I'd be especially grateful if > you both had a quick look. Some major points: > > 1) I have added support for AVX 512, although this is necessarily > untested. AVX and AVX2 are also both supported. > > 2) After the recent churn regarding patching LLVM's GHC calling > convention, by default only 128-bit wide SIMD vectors are passed in > registers, and then only on X86_64. There is a "hidden" flag, > -fllvm-pass-vectors-in-regs, that causes GHC to generate LLVM code that > assumes all vectors are passed in registers by LLVM. This can be used > with a suitably patched version of LLVM, and if we get LLVM 3.4 patched, > we can consider turning it on by default for LLVM 3.4+. This would mean > that we couldn't mix LLVM <3.3-compiled object files with LLVM > >3.4-compiled object files, but I don't see that as much of a problem. > > 3) utils/genprimcode has been hacked up to allow us to write vector > operations once and have them instantiated at multiple vector types. I'm > not thrilled with this solution, but after discussing with Simon PJ, > what I've implemented seems to be the minimal reasonable solution to the > problem of exploding primop boilerplate. The changes are documented in > compiler/prelude/primops.txt.pp. > > 4) Error handling is sub-optimal. My patch checks to make sure that > vector primops can be compiled efficiently based on the current set of > dynamic flags. For example, if -mavx is not specified and the user tries > to use a primop that adds together two 256-bit wide vectors of > double-precision elements, the user will see an error message like: > > ghc-stage2: sorry! (unimplemented feature or known bug) > (GHC version 7.7.20130916 for x86_64-unknown-linux): > 256-bit wide floating point SIMD vector instructions require at > least -mavx. > > This is because the only good place to check for this kind of error is > during STG->Cmm translation (in compiler/codeGen/StgCmmPrim.hs), and we > don't have much of an error handling infrastructure there in contrast to > when we're working in the typechecking/renaming monad. If there is a > better way/place to do this, please let me know. > > Thanks, > Geoff > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://www.haskell.org/mailman/listinfo/ghc-devs >
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