[commit: ghc] master: Discard reflexive casts during Simplify (7bb7f99)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/7bb7f991e2b04b7daed079bab9e63884404802a0/ghc

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

commit 7bb7f991e2b04b7daed079bab9e63884404802a0
Author: Richard Eisenberg <rae at cs.brynmawr.edu>
Date:   Tue Apr 10 10:23:42 2018 -0400

    Discard reflexive casts during Simplify
    
    Trac #14735 (derived from Trac #11735) found that 75% of compile
    time was being spent in simplCast. This patch is the first in a series
    to deal with that problem.
    
    This particular patch actually has very little effect on performance; it
    just refactors simplCast so that it builds Refl coercions less often.
    Refl coercions require us to compute the type to put inside them, and
    even if that's done lazily it is still work and code. Instead we use
    Maybe Coercion with Nothing for Refl. This change also percolates to
    pushCoTyArg and pushValArg.
    
    Reviewers: goldfire, bgamari, simonpj
    
    Reviewed By: simonpj
    
    Subscribers: rwbarton, thomie, carter
    
    GHC Trac Issues: #14737
    
    Differential Revision: https://phabricator.haskell.org/D4395


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

7bb7f991e2b04b7daed079bab9e63884404802a0
 compiler/coreSyn/CoreOpt.hs    | 48 +++++++++++++----------
 compiler/simplCore/Simplify.hs | 89 +++++++++++++++++++++++-------------------
 2 files changed, 76 insertions(+), 61 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 7bb7f991e2b04b7daed079bab9e63884404802a0