[PATCH] D144848: [SCEV] Skip instrs with non-scevable types in forget[Loop,Value].

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: mkazantsev, nikic, reames.
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No SCEVs are formed for instructions with non-scevable types, so no
other SCEV expressions can depend on them. Skip those instructions and
their users when invalidating SCEV expressions.

To catch potential missed cases, the full def-use chains are traversed
after the cleanup to assert no entries in ValueExprMap remain.

Depends on D144847 <https://reviews.llvm.org/D144847>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D144848

Files:
  llvm/include/llvm/Analysis/ScalarEvolution.h
  llvm/lib/Analysis/ScalarEvolution.cpp


Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -8441,6 +8441,8 @@
     SmallVectorImpl<const SCEV *> &ToForget) {
   while (!Worklist.empty()) {
     Instruction *I = Worklist.pop_back_val();
+    if (!isSCEVable(I->getType()))
+      continue;
 
     ValueExprMapType::iterator It =
         ValueExprMap.find_as(static_cast<Value *>(I));
@@ -8455,12 +8457,32 @@
   }
 }
 
+#ifndef NDEBUG
+void ScalarEvolution::verifyAllUsersClearedFromMap(
+    SmallVectorImpl<Instruction *> &Worklist,
+    SmallPtrSetImpl<Instruction *> &Visited) {
+  while (!Worklist.empty()) {
+    Instruction *I = Worklist.pop_back_val();
+    if (!isSCEVable(I->getType()))
+      continue;
+    assert(ValueExprMap.count(I) == 0 &&
+           "entry for I has not been removed properly");
+    PushDefUseChildren(I, Worklist, Visited);
+  }
+}
+#endif
+
 void ScalarEvolution::forgetLoop(const Loop *L) {
   SmallVector<const Loop *, 16> LoopWorklist(1, L);
   SmallVector<Instruction *, 32> Worklist;
   SmallPtrSet<Instruction *, 16> Visited;
   SmallVector<const SCEV *, 16> ToForget;
 
+#ifndef NDEBUG
+  SmallVector<Instruction *, 16> VerificationWorklist;
+  SmallPtrSet<Instruction *, 8> VerificationVisited;
+#endif
+
   // Iterate over all the loops and sub-loops to drop SCEV information.
   while (!LoopWorklist.empty()) {
     auto *CurrL = LoopWorklist.pop_back_val();
@@ -8487,6 +8509,9 @@
 
     // Drop information about expressions based on loop-header PHIs.
     PushLoopPHIs(CurrL, Worklist, Visited);
+#ifndef NDEBUG
+    PushLoopPHIs(CurrL, VerificationWorklist, VerificationVisited);
+#endif
     visitAndClearUsers(Worklist, Visited, ToForget);
 
     LoopPropertiesCache.erase(CurrL);
@@ -8495,6 +8520,10 @@
     LoopWorklist.append(CurrL->begin(), CurrL->end());
   }
   forgetMemoizedResults(ToForget);
+
+#ifndef NDEBUG
+  verifyAllUsersClearedFromMap(VerificationWorklist, VerificationVisited);
+#endif
 }
 
 void ScalarEvolution::forgetTopmostLoop(const Loop *L) {
@@ -8514,6 +8543,14 @@
   visitAndClearUsers(Worklist, Visited, ToForget);
 
   forgetMemoizedResults(ToForget);
+
+#ifndef NDEBUG
+  SmallVector<Instruction *, 16> VerificationWorklist;
+  SmallPtrSet<Instruction *, 8> VerificationVisited;
+  Worklist.push_back(cast<Instruction>(V));
+  Visited.insert(cast<Instruction>(V));
+  verifyAllUsersClearedFromMap(VerificationWorklist, VerificationVisited);
+#endif
 }
 
 void ScalarEvolution::forgetLoopDispositions() { LoopDispositions.clear(); }
Index: llvm/include/llvm/Analysis/ScalarEvolution.h
===================================================================
--- llvm/include/llvm/Analysis/ScalarEvolution.h
+++ llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -2045,6 +2045,13 @@
                           SmallPtrSetImpl<Instruction *> &Visited,
                           SmallVectorImpl<const SCEV *> &ToForget);
 
+#ifndef NDEBUG
+  /// Iterate over instructions in \p Worlist and their users. Assert all users
+  /// have been removed from ValueExprMap.
+  void verifyAllUsersClearedFromMap(SmallVectorImpl<Instruction *> &Worklist,
+                                    SmallPtrSetImpl<Instruction *> &Visited);
+#endif
+
   /// Return an existing SCEV for V if there is one, otherwise return nullptr.
   const SCEV *getExistingSCEV(Value *V);
 


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