[commit: ghc] master: cmm/CBE: Collapse blocks equivalent up to alpha renaming of local registers (7920a7d)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/7920a7d9c53083b234e060a3e72f00b601a46808/ghc

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commit 7920a7d9c53083b234e060a3e72f00b601a46808
Author: Ben Gamari <bgamari.foss at gmail.com>
Date:   Tue Sep 19 16:57:41 2017 -0400

    cmm/CBE: Collapse blocks equivalent up to alpha renaming of local registers
    
    As noted in #14226, the common block elimination pass currently
    implements an extremely strict equivalence relation, demanding that two
    blocks are equivalent including the names of their local registers. This
    is quite restrictive and severely hampers the effectiveness of the pass.
    
    Here we allow the CBE pass to collapse blocks which are equivalent up to
    alpha renaming of locally-bound local registers. This is completely safe
    and catches many more duplicate blocks.
    
    Test Plan: Validate
    
    Reviewers: austin, simonmar, michalt
    
    Reviewed By: michalt
    
    Subscribers: rwbarton, thomie
    
    GHC Trac Issues: #14226
    
    Differential Revision: https://phabricator.haskell.org/D3973


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7920a7d9c53083b234e060a3e72f00b601a46808
 compiler/cmm/CmmCommonBlockElim.hs | 237 ++++++++++++++++++++++++++++---------
 compiler/cmm/Hoopl/Block.hs        |   1 +
 2 files changed, 180 insertions(+), 58 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 7920a7d9c53083b234e060a3e72f00b601a46808