Jakub Kuderski e25b7db874 [Dominators] Include infinite loops in PostDominatorTree ... Summary: This patch teaches PostDominatorTree about infinite loops. It is built on top of D29705 by @dberlin which includes a very detailed motivation for this change. What's new is that the patch also teaches the incremental updater how to deal with reverse-unreachable regions and how to properly maintain and verify tree roots. Before that, the incremental algorithm sometimes ended up preserving reverse-unreachable regions after updates that wouldn't appear in the tree if it was constructed from scratch on the same CFG. This patch makes the following assumptions: - A sequence of updates should produce the same tree as a recalculating it. - Any sequence of the same updates should lead to the same tree. - Siblings and roots are unordered. The last two properties are essential to efficiently perform batch updates in the future. When it comes to the first one, we can decide later that the consistency between freshly built tree and an updated one doesn't matter match, as there are many correct ways to pick roots in infinite loops, and to relax this assumption. That should enable us to recalculate postdominators less frequently. This patch is pretty conservative when it comes to incremental updates on reverse-unreachable regions and ends up recalculating the whole tree in many cases. It should be possible to improve the performance in many cases, if we decide that it's important enough. That being said, my experiments showed that reverse-unreachable are very rare in the IR emitted by clang when bootstrapping clang. Here are the statistics I collected by analyzing IR between passes and after each removePredecessor call: ``` # functions: 52283 # samples: 337609 # reverse unreachable BBs: 216022 # BBs: 247840796 Percent reverse-unreachable: 0.08716159869015269 % Max(PercRevUnreachable) in a function: 87.58620689655172 % # > 25 % samples: 471 ( 0.1395104988314885 % samples ) ... in 145 ( 0.27733680163724345 % functions ) ``` Most of the reverse-unreachable regions come from invalid IR where it wouldn't be possible to construct a PostDomTree anyway. I would like to commit this patch in the next week in order to be able to complete the work that depends on it before the end of my internship, so please don't wait long to voice your concerns :). Reviewers: dberlin, sanjoy, grosser, brzycki, davide, chandlerc, hfinkel Reviewed By: dberlin Subscribers: nhaehnle, javed.absar, kparzysz, uabelho, jlebar, hiraditya, llvm-commits, dberlin, david2050 Differential Revision: https://reviews.llvm.org/D35851 llvm-svn: 310940		2017-08-15 18:14:57 +00:00
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AsmWriterTest.cpp	Re-sort #include lines for unittests. This uses a slightly modified	2017-06-06 11:06:56 +00:00
AttributesTest.cpp	Fix assertion when merging multiple empty AttributeLists	2017-05-31 14:24:06 +00:00
BasicBlockTest.cpp	Remove unnecessary double-assignment triggering -Wsequence-point.	2017-05-26 12:07:12 +00:00
CFGBuilder.cpp	[Dominators] Define Arc less-than operator inline.	2017-07-13 23:11:57 +00:00
CFGBuilder.h	[Dominators] Define Arc less-than operator inline.	2017-07-13 23:11:57 +00:00
CMakeLists.txt	[Dominators] Add CFGBuilder testing utility	2017-07-13 21:16:01 +00:00
ConstantRangeTest.cpp	[ConstantRange] Add another truncate unittest for wrapped set staying a wrapped set.	2017-06-04 23:07:53 +00:00
ConstantsTest.cpp	Re-sort #include lines for unittests. This uses a slightly modified	2017-06-06 11:06:56 +00:00
DebugInfoTest.cpp
DebugTypeODRUniquingTest.cpp	Re-sort #include lines for unittests. This uses a slightly modified	2017-06-06 11:06:56 +00:00
DominatorTreeTest.cpp	[Dominators] Include infinite loops in PostDominatorTree	2017-08-15 18:14:57 +00:00
FunctionTest.cpp
InstructionsTest.cpp	[IR] De-virtualize ~Value to save a vptr	2017-05-18 17:24:10 +00:00
IntrinsicsTest.cpp
IRBuilderTest.cpp	Debug Info: Add a file: field to DIImportedEntity.	2017-07-19 00:09:54 +00:00
LegacyPassManagerTest.cpp
MDBuilderTest.cpp
MetadataTest.cpp	Disable some IR death tests when SEH is available	2017-08-10 21:14:07 +00:00
ModuleTest.cpp	Have Module::createRNG return a unique_ptr	2017-07-12 08:03:44 +00:00
PassBuilderCallbacksTest.cpp	[PM] Enable registration of out-of-tree passes with PassBuilder	2017-07-10 10:57:55 +00:00
PassManagerTest.cpp	[PM] Teach PreservedAnalyses to have an allInSet static factory	2017-07-09 07:23:27 +00:00
PatternMatch.cpp	Fix m_[Ord|Unord][FMin|FMax] matchers to correctly match ordering.	2017-06-13 17:18:45 +00:00
TypeBuilderTest.cpp
TypesTest.cpp
UserTest.cpp	Re-sort #include lines for unittests. This uses a slightly modified	2017-06-06 11:06:56 +00:00
UseTest.cpp
ValueHandleTest.cpp
ValueMapTest.cpp
ValueTest.cpp	Re-sort #include lines for unittests. This uses a slightly modified	2017-06-06 11:06:56 +00:00
VerifierTest.cpp	Re-sort #include lines for unittests. This uses a slightly modified	2017-06-06 11:06:56 +00:00
WaymarkTest.cpp