cmm: Revert more aggressive CBE due to #14226
authorBen Gamari <ben@smart-cactus.org>
Sun, 4 Feb 2018 00:49:21 +0000 (19:49 -0500)
committerBen Gamari <ben@smart-cactus.org>
Sun, 4 Feb 2018 01:36:15 +0000 (20:36 -0500)
commitf0cae1f24ecc34ab06e87c6c7423d45917ba593e
tree2c70cc80f99d3aa41b1065ccd92acd47ba6c6a42
parent5acecda09076663aaf64d0b33f228170f97c841d
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.

(cherry picked from commit 50adbd7c5fe5894d3e6e2a58b353ed07e5f8949d)
compiler/cmm/CmmCommonBlockElim.hs
compiler/cmm/CmmPipeline.hs
compiler/cmm/Hoopl/Block.hs