[commit: ghc] ghc-8.0: Defer inlining of Eq for primitive types (ed3398d)

[git at git.haskell.org]

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

On branch  : ghc-8.0
Link       : http://ghc.haskell.org/trac/ghc/changeset/ed3398d176fc777dff8f5ae5315425e40c705c2d/ghc

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

commit ed3398d176fc777dff8f5ae5315425e40c705c2d
Author: Ben Gamari <bgamari.foss at gmail.com>
Date:   Thu Mar 24 11:24:32 2016 +0100

    Defer inlining of Eq for primitive types
    
    Summary:
    This is one solution to #11688, wherein (==) was inlined to soon
    defeating a rewrite rule provided by bytestring. Since the RHSs of Eq's
    methods are simple, there is little to be gained and much to be lost by
    inlining them early.
    
    For instance, the bytestring library provides,
    
    ```lang=haskell
    break :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
    breakByte :: Word8 -> ByteString -> (ByteString, ByteString)
    ```
    
    and a rule
    
    ```
    forall x. break ((==) x) = breakByte x
    ```
    
    since `breakByte` implments an optimized version of `break (== x)` for
    known `x :: Word8`. If we allow `(==)` to be inlined too early, we will
    prevent this rule from firing. This was the cause of #11688.
    
    This patch just defers the `Eq` methods, although it's likely worthwhile
    giving `Ord` this same treatment. This regresses compiler allocations
    for T9661 by about 8% due to the additional inlining that we now require
    the simplifier to perform.
    
    Updates the `bytestring` submodule to include updated rewrite rules
    which match on `eqWord8` instead of `(==)`.
    
    Test Plan:
     * Validate, examine performance impact
    
    Reviewers: simonpj, hvr, austin
    
    Subscribers: thomie
    
    Differential Revision: https://phabricator.haskell.org/D1980
    
    GHC Trac Issues: #11688
    
    (cherry picked from commit 0bd0c31e833055eb3e86177f70c4b4d93d5a1c11)


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

ed3398d176fc777dff8f5ae5315425e40c705c2d
 libraries/base/GHC/Char.hs          |  9 +++-
 libraries/base/GHC/Float.hs         | 20 +++++----
 libraries/base/GHC/Int.hs           | 74 +++++++++++++++++++++++++++----
 libraries/base/GHC/Word.hs          | 77 +++++++++++++++++++++++++++++---
 libraries/ghc-prim/GHC/Classes.hs   | 87 +++++++++++++++++++++++++++++++++----
 testsuite/tests/perf/compiler/all.T |  5 ++-
 6 files changed, 236 insertions(+), 36 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 ed3398d176fc777dff8f5ae5315425e40c705c2d