[commit: ghc] master: Invert FP conditions to eliminate the explicit NaN check. (6bb9bc7)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/6bb9bc7d3c935dcb77e0700cce28de2c9df646df/ghc

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commit 6bb9bc7d3c935dcb77e0700cce28de2c9df646df
Author: klebinger.andreas at gmx.at <klebinger.andreas at gmx.at>
Date:   Tue Sep 18 17:46:38 2018 +0200

    Invert FP conditions to eliminate the explicit NaN check.
    
    Summary:
    Optimisation: we don't have to test the parity flag if we
    know the test has already excluded the unordered case: eg >
    and >= test for a zero carry flag, which can only occur for
    ordered operands.
    
    By reversing comparisons we can avoid testing the parity
    for < and <= as well. This works since:
    * If any of the arguments is an NaN CF gets set. Resulting in a false result.
    * Since this allows us to rule out NaN we can exchange the arguments and invert the
      direction of the arrows.
    
    Test Plan: ci/nofib
    
    Reviewers: carter, bgamari, alpmestan
    
    Reviewed By: alpmestan
    
    Subscribers: alpmestan, simonpj, jmct, rwbarton, thomie
    
    GHC Trac Issues: #15196
    
    Differential Revision: https://phabricator.haskell.org/D4990


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6bb9bc7d3c935dcb77e0700cce28de2c9df646df
 compiler/nativeGen/X86/CodeGen.hs                  | 100 ++++++++++++++++-----
 testsuite/tests/codeGen/should_compile/Makefile    |   3 +
 testsuite/tests/codeGen/should_compile/T15196.hs   |   4 +
 .../tests/codeGen/should_compile/T15196.stdout     |   1 +
 testsuite/tests/codeGen/should_compile/all.T       |   6 ++
 5 files changed, 92 insertions(+), 22 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 6bb9bc7d3c935dcb77e0700cce28de2c9df646df