Commit Graph

3 Commits

Author SHA1 Message Date
Roman Lebedev 04d3d3bbff [InstCombine] (Y + ~X) + 1 --> Y - X fold (PR42459)
Summary:
To be noted, this pattern is not unhandled by instcombine per-se,
it is somehow does end up being folded when one runs opt -O3,
but not if it's just -instcombine. Regardless, that fold is
indirect, depends on some other folds, and is thus blind
when there are extra uses.

This does address the regression being exposed in D63992.

https://godbolt.org/z/7DGltU
https://rise4fun.com/Alive/EPO0

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=42459 | PR42459 ]]

Reviewers: spatel, nikic, huihuiz

Reviewed By: spatel

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63993

llvm-svn: 364792
2019-07-01 15:55:24 +00:00
Roman Lebedev 9f3645869c [NFC][InstCombine] Improve test coverage for ((~x) + y) + 1 -> y - x fold fold (PR42459)
So we indeed to have this fold, but only if +1 is not the last operation..

llvm-svn: 364764
2019-07-01 13:31:06 +00:00
Roman Lebedev d5c3e34cb7 [NFC][InstCombine] Tests for ((~x) + y) + 1 -> y - x fold fold (PR42459)
To be noted, this pattern is not unhandled by instcombine per-se,
it is somehow does end up being folded when one runs opt -O3,
but not if it's just -instcombine. Regardless, that fold is
indirect, depends on some other folds, and is thus blind
when there are extra uses.

https://bugs.llvm.org/show_bug.cgi?id=42459
https://rise4fun.com/Alive/EPO0

llvm-svn: 364749
2019-07-01 12:22:06 +00:00