Commit Graph

5 Commits

Author SHA1 Message Date
Eric Christopher cee313d288 Revert "Temporarily Revert "Add basic loop fusion pass.""
The reversion apparently deleted the test/Transforms directory.

Will be re-reverting again.

llvm-svn: 358552
2019-04-17 04:52:47 +00:00
Eric Christopher a863435128 Temporarily Revert "Add basic loop fusion pass."
As it's causing some bot failures (and per request from kbarton).

This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.

llvm-svn: 358546
2019-04-17 02:12:23 +00:00
Max Kazantsev 7b78d3920c [MustExecute] Fix algorithmic bug in isGuaranteedToExecute. PR38514
The description of `isGuaranteedToExecute` does not correspond to its implementation.
According to description, it should return `true` if an instruction is executed under the
assumption that its loop is *entered*. However there is a sophisticated alrogithm inside
that tries to prove that the instruction is executed if the loop is *exited*, which is not the
same thing for infinite loops. There is an attempt to protect from dealing with infinite loops
by prohibiting loops without exit blocks, however an infinite loop can have exit blocks.

As result of that, MustExecute can falsely consider some blocks that are never entered as
mustexec, and LICM can hoist dangerous instructions out of them basing on this fact.
This may introduce UB to programs which did not contain it initially.

This patch removes the problematic algorithm and replaced it with a one which tries to
prove what is required in description.

Differential Revision: https://reviews.llvm.org/D50558
Reviewed By: reames

llvm-svn: 339984
2018-08-17 06:19:17 +00:00
Max Kazantsev cfa3e66b8e [NFC] Add tests to ensure that improvement of MustThrow analysis will not lead to problems in future
llvm-svn: 339983
2018-08-17 05:20:25 +00:00
Max Kazantsev 4e9def57c7 [NFC] Add tests that demonstrate that MustExecute is fundamentally broken
llvm-svn: 339417
2018-08-10 09:20:46 +00:00