Commit Graph

8 Commits

Author SHA1 Message Date
Sanjay Patel 2f7c24fe30 [InstCombine] (A + B) + B --> A + (B << 1)
This eliminates a use of 'B', so it can enable follow-on transforms
as well as improve analysis/codegen.

The PhaseOrdering test was added for D61726, and that shows
the limits of instcombine vs. real reassociation. We would
need to run some form of CSE to collapse that further.

The intermediate variable naming here is intentional because
there's a test at llvm/test/Bitcode/value-with-long-name.ll
that would break with the usual nameless value. I'm not sure
how to improve that test to be more robust.

The naming may also be helpful to debug regressions if this
change exposes weaknesses in the reassociation pass for example.
2020-05-22 11:46:59 -04:00
Sanjay Patel 5a230a19ad [PhaseOrdering] regenerate test checks; NFC
Remove some redundant/unnecessary bits too.
2020-05-22 10:10:47 -04:00
Roman Lebedev 1badf7c33a
[InstComine] Forego of one-use check in `(X - (X & Y)) --> (X & ~Y)` if Y is a constant
Summary:
This is potentially more friendly for further optimizations,
analysies, e.g.: https://godbolt.org/z/G24anE

This resolves phase-ordering bug that was introduced
in D75145 for https://godbolt.org/z/2gBwF2
https://godbolt.org/z/XvgSua

Reviewers: spatel, nikic, dmgreen, xbolva00

Reviewed By: nikic, xbolva00

Subscribers: hiraditya, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75757
2020-03-06 21:39:07 +03:00
Nemanja Ivanovic 1d662316cb [Pass Pipeline][NFC] Add a test prior to committing D61726
This patch just adds a test case to show the differences in code emitted
by opt before and after https://reviews.llvm.org/D61726.

Previous attempt to commit this did not include the registered target
requirement so it caused buildbot breaks.

llvm-svn: 360620
2019-05-13 21:14:36 +00:00
Nemanja Ivanovic 34dc3aca40 Pull r360426 as it is breaking the build bots.
llvm-svn: 360437
2019-05-10 16:03:22 +00:00
Nemanja Ivanovic 7a41cd5b88 Another attempt to fix the build bot breaks after r360426
The test case checks were produced by the update_test_checks.py
scripts and I assumed that is sufficient. However, the behaviour
is different with different default target triples. Specify the
triple explicitly in the test case.

If this doesn't clean up the build bot breaks, I'll remove the test
case until I can get to the bottom of why the behaviour on build bots
is different from my machine.

llvm-svn: 360434
2019-05-10 15:44:56 +00:00
Nemanja Ivanovic 0f991c65f2 Fix build break after r360426
llvm-svn: 360433
2019-05-10 15:11:40 +00:00
Nemanja Ivanovic cfc89896e0 [Pass Pipeline][NFC] Add a test prior to committing D61726
This patch just adds a test case to show the differences in code emitted
by opt before and after https://reviews.llvm.org/D61726.

llvm-svn: 360426
2019-05-10 13:47:00 +00:00