[PATCH] D94138: Require chained analyses in BasicAA and AAResults to be transitive

[Bjorn Pettersson via Phabricator via llvm-commits]

bjope created this revision.
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This patch fixes a bug that could result in miscompiles (at least
in an OOT target). The problem could be seen by adding checks that
the DominatorTree used in BasicAliasAnalysis and ValueTracking was
valid (e.g. by adding DT->verify() call before every DT dereference
and then running all tests in test/CodeGen).

Problem was that the LegacyPassManager calculated "last user"
incorrectly for passes such as the DominatorTree when not telling
the pass manager that there was a transitive dependency between
the different analyses. And then it could happen that an incorrect
dominator tree was used when doing alias analysis (which was a pretty
serious bug as the alias analysis result could be invalid).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94138

Files:
  llvm/lib/Analysis/AliasAnalysis.cpp
  llvm/lib/Analysis/BasicAliasAnalysis.cpp
  llvm/lib/Target/Hexagon/HexagonLoopIdiomRecognition.cpp
  llvm/lib/Transforms/Scalar/GVNHoist.cpp


Index: llvm/lib/Transforms/Scalar/GVNHoist.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/GVNHoist.cpp
+++ llvm/lib/Transforms/Scalar/GVNHoist.cpp
@@ -547,7 +547,6 @@
     AU.addPreserved<DominatorTreeWrapperPass>();
     AU.addPreserved<MemorySSAWrapperPass>();
     AU.addPreserved<GlobalsAAWrapperPass>();
-    AU.addPreserved<AAResultsWrapperPass>();
   }
 };
 
Index: llvm/lib/Target/Hexagon/HexagonLoopIdiomRecognition.cpp
===================================================================
--- llvm/lib/Target/Hexagon/HexagonLoopIdiomRecognition.cpp
+++ llvm/lib/Target/Hexagon/HexagonLoopIdiomRecognition.cpp
@@ -165,7 +165,6 @@
     AU.addRequiredID(LoopSimplifyID);
     AU.addRequiredID(LCSSAID);
     AU.addRequired<AAResultsWrapperPass>();
-    AU.addPreserved<AAResultsWrapperPass>();
     AU.addRequired<ScalarEvolutionWrapperPass>();
     AU.addRequired<DominatorTreeWrapperPass>();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1875,9 +1875,9 @@
 
 void BasicAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
-  AU.addRequired<AssumptionCacheTracker>();
-  AU.addRequired<DominatorTreeWrapperPass>();
-  AU.addRequired<TargetLibraryInfoWrapperPass>();
+  AU.addRequiredTransitive<AssumptionCacheTracker>();
+  AU.addRequiredTransitive<DominatorTreeWrapperPass>();
+  AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>();
   AU.addUsedIfAvailable<PhiValuesWrapperPass>();
 }
 
Index: llvm/lib/Analysis/AliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/AliasAnalysis.cpp
+++ llvm/lib/Analysis/AliasAnalysis.cpp
@@ -883,8 +883,8 @@
 
 void AAResultsWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
-  AU.addRequired<BasicAAWrapperPass>();
-  AU.addRequired<TargetLibraryInfoWrapperPass>();
+  AU.addRequiredTransitive<BasicAAWrapperPass>();
+  AU.addRequiredTransitive<TargetLibraryInfoWrapperPass>();
 
   // We also need to mark all the alias analysis passes we will potentially
   // probe in runOnFunction as used here to ensure the legacy pass manager


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