Xing Xue f84383727e [MustExecute] Improve MustExecute to correctly handle loop nest ... Summary: for.outer: br for.inner for.inner: LI <loop invariant load instruction> for.inner.latch: br for.inner, for.outer.latch for.outer.latch: br for.outer, for.outer.exit LI is a loop invariant load instruction that post dominate for.outer, so LI should be able to move out of the loop nest. However, there is a bug in allLoopPathsLeadToBlock(). Current algorithm of allLoopPathsLeadToBlock() 1. get all the transitive predecessors of the basic block LI belongs to (for.inner) ==> for.outer, for.inner.latch 2. if any successors of any of the predecessors are not for.inner or for.inner's predecessors, then return false 3. return true Although for.inner.latch is for.inner's predecessor, but for.inner dominates for.inner.latch, which means if for.inner.latch is ever executed, for.inner should be as well. It should not return false for cases like this. Author: Whitney (committed by xingxue) Reviewers: kbarton, jdoerfert, Meinersbur, hfinkel, fhahn Reviewed By: jdoerfert Subscribers: hiraditya, jsji, llvm-commits, etiotto, bmahjour Tags: #LLVM Differential Revision: https://reviews.llvm.org/D62418 llvm-svn: 361762		2019-05-27 13:57:28 +00:00
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const-cond.ll
infinite_loops.ll
loop-header.ll	[MustExecute] Improve MustExecute to correctly handle loop nest	2019-05-27 13:57:28 +00:00