[commit: ghc] master: cmm: Revert more aggressive CBE due to #14226 (50adbd7)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/50adbd7c5fe5894d3e6e2a58b353ed07e5f8949d/ghc

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commit 50adbd7c5fe5894d3e6e2a58b353ed07e5f8949d
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Sat Feb 3 19:49:21 2018 -0500

    cmm: Revert more aggressive CBE due to #14226
    
    Trac #14226 noted that the C-- CBE pass frequently fails to
    common up semantically identical blocks due to the differences in local
    register naming. These patches fixed this by making the pass consider
    equality up to alpha-renaming.
    
    However, the new logic failed to consider the possibility that local
    register naming *may* matter across multiple blocks. This lead to the
    regression #14754. I'll need to do a bit of thinking on a proper
    solution to this but in the meantime I'm reverting all four patches.
    
    This reverts commit a27056f9823f8bbe2302f1924b3ab38fd6752e37.
    This reverts commit 6f990c54f922beae80362fe62426beededc21290.
    This reverts commit 9aa73892e10e90a1799b9277da593e816a827364.
    This reverts commit 7920a7d9c53083b234e060a3e72f00b601a46808.


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50adbd7c5fe5894d3e6e2a58b353ed07e5f8949d
 compiler/cmm/CmmCommonBlockElim.hs | 320 ++++++++++---------------------------
 compiler/cmm/CmmPipeline.hs        |   2 +-
 compiler/cmm/Hoopl/Block.hs        |   1 -
 3 files changed, 86 insertions(+), 237 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 50adbd7c5fe5894d3e6e2a58b353ed07e5f8949d