Fix assertion in LICM doFinalization()

The doFinalization method checks that the LoopToAliasSetMap is
empty. LICM populates that map as it runs through the loop nest,
deleting the entries for child loops as it goes. However, if a child
loop is deleted by another pass (e.g. unrolling) then the loop will
never be deleted from the map because LICM walks the loop nest to
find entries it can delete.

The fix is to delete the loop from the map and free the alias set
when the loop is deleted from the loop nest.

Differential Revision: http://reviews.llvm.org/D5305

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218387 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/LoopPass.h b/include/llvm/Analysis/LoopPass.h
index 726e28636ac61aed59c6695becccac96602739cd..8650000fcfb6ede62f7ded42a1c0780861ee52c6 100644 (file)
--- a/include/llvm/Analysis/LoopPass.h
+++ b/include/llvm/Analysis/LoopPass.h
@@ -82,6 +82,11 @@ public:
   /// deleteAnalysisValue - Delete analysis info associated with value V.
   virtual void deleteAnalysisValue(Value *V, Loop *L) {}
 
+  /// Delete analysis info associated with Loop L.
+  /// Called to notify a Pass that a loop has been deleted and any
+  /// associated analysis values can be deleted.
+  virtual void deleteAnalysisLoop(Loop *L) {}
+
 protected:
   /// skipOptnoneFunction - Containing function has Attribute::OptimizeNone
   /// and most transformation passes should skip it.
@@ -152,6 +157,10 @@ public:
   /// that implement simple analysis interface.
   void deleteSimpleAnalysisValue(Value *V, Loop *L);
 
+  /// Invoke deleteAnalysisLoop hook for all passes that implement simple
+  /// analysis interface.
+  void deleteSimpleAnalysisLoop(Loop *L);
+
 private:
   std::deque<Loop *> LQ;
   bool skipThisLoop;

diff --git a/lib/Analysis/LoopPass.cpp b/lib/Analysis/LoopPass.cpp
index 7bd866e73e10f370100e06ce148f34876deb60b6..190abc73fbb466c38248afd3424e7dec8bae2682 100644 (file)
--- a/lib/Analysis/LoopPass.cpp
+++ b/lib/Analysis/LoopPass.cpp
@@ -76,6 +76,9 @@ void LPPassManager::deleteLoopFromQueue(Loop *L) {
 
   LI->updateUnloop(L);
 
+  // Notify passes that the loop is being deleted.
+  deleteSimpleAnalysisLoop(L);
+
   // If L is current loop then skip rest of the passes and let
   // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
   // and continue applying other passes on CurrentLoop.
@@ -164,6 +167,14 @@ void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
   }
 }
 
+/// Invoke deleteAnalysisLoop hook for all passes.
+void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
+  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
+    LoopPass *LP = getContainedPass(Index);
+    LP->deleteAnalysisLoop(L);
+  }
+}
+
 
 // Recurse through all subloops and all loops  into LQ.
 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index d387b56689af80fa1448d76f0ff447c2714cfd32..4952a644ff2540e2ef2b17f7eacefe2dbdfe78a9 100644 (file)
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -130,6 +130,9 @@ namespace {
     /// set.
     void deleteAnalysisValue(Value *V, Loop *L) override;
 
+    /// Simple Analysis hook. Delete loop L from alias set map.
+    void deleteAnalysisLoop(Loop *L) override;
+
     /// SinkRegion - Walk the specified region of the CFG (defined by all blocks
     /// dominated by the specified block, and that are in the current loop) in
     /// reverse depth first order w.r.t the DominatorTree.  This allows us to
@@ -943,3 +946,13 @@ void LICM::deleteAnalysisValue(Value *V, Loop *L) {
 
   AST->deleteValue(V);
 }
+
+/// Simple Analysis hook. Delete value L from alias set map.
+void LICM::deleteAnalysisLoop(Loop *L) {
+  AliasSetTracker *AST = LoopToAliasSetMap.lookup(L);
+  if (!AST)
+    return;
+
+  delete AST;
+  LoopToAliasSetMap.erase(L);
+}

diff --git a/test/Transforms/LICM/2014-09-10-doFinalizationAssert.ll b/test/Transforms/LICM/2014-09-10-doFinalizationAssert.ll
new file mode 100644 (file)
index 0000000..17ae716
--- /dev/null
+++ b/test/Transforms/LICM/2014-09-10-doFinalizationAssert.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -scalar-evolution -licm -loop-unroll -disable-output
+; Test triggered an assertion in doFinalization() because loop unroll was deleting
+; the inner loop which caused the loop to not get removed from the
+; LoopToAliasSetMap.
+; Test case taken from test/Transforms/LoopUnroll/unloop.ll.
+
+declare i1 @check() nounwind
+define void @skiplevelexit() nounwind {
+entry:
+  br label %outer
+
+outer:
+  br label %inner
+
+inner:
+  %iv = phi i32 [ 0, %outer ], [ %inc, %tail ]
+  %inc = add i32 %iv, 1
+  call zeroext i1 @check()
+  br i1 true, label %outer.backedge, label %tail
+
+tail:
+  br i1 false, label %inner, label %exit
+
+outer.backedge:
+  br label %outer
+
+exit:
+  ret void
+}
+