[commit: ghc] master: Generate better fp abs for X86 and llvm with default cmm otherwise (12ccf76)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/12ccf767af3373e319b75d5d61fe79df4a389e45/ghc

>---------------------------------------------------------------

commit 12ccf767af3373e319b75d5d61fe79df4a389e45
Author: Dominic Steinitz <dominic at steinitz.org>
Date:   Tue Mar 7 09:26:16 2017 -0500

    Generate better fp abs for X86 and llvm with default cmm otherwise
    
    Currently we have this in libraries/base/GHC/Float.hs:
    ```
    abs x | x == 0    = 0 -- handles (-0.0)
          | x >  0    = x
          | otherwise = negateFloat x
    ```
    But 3-4 years ago it was noted that this was inefficient:
    https://mail.haskell.org/pipermail/libraries/2013-April/019690.html
    
    We can generate better code for X86 and llvm and for others generate
    some custom cmm code which is similar to what the compiler generates
    now.
    
    Reviewers: austin, simonmar, hvr, bgamari
    
    Reviewed By: bgamari
    
    Subscribers: dfeuer, thomie
    
    Differential Revision: https://phabricator.haskell.org/D3265


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12ccf767af3373e319b75d5d61fe79df4a389e45
 compiler/cmm/CmmMachOp.hs               |  2 ++
 compiler/cmm/PprC.hs                    |  2 ++
 compiler/codeGen/StgCmmPrim.hs          | 34 ++++++++++++++++++++++++++
 compiler/llvmGen/LlvmCodeGen/CodeGen.hs |  2 ++
 compiler/nativeGen/PPC/CodeGen.hs       |  2 ++
 compiler/nativeGen/SPARC/CodeGen.hs     |  2 ++
 compiler/nativeGen/X86/CodeGen.hs       | 42 +++++++++++++++++++++++++++++----
 compiler/nativeGen/X86/Ppr.hs           |  2 ++
 compiler/prelude/primops.txt.pp         |  4 ++++
 libraries/base/GHC/Float.hs             | 14 +++++------
 10 files changed, 94 insertions(+), 12 deletions(-)

Diff suppressed because of size. To see it, use:

    git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc 12ccf767af3373e319b75d5d61fe79df4a389e45