[PATCH] D77855: [CallGraphUpdater] Remove nodes from their SCC (old PM)

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert created this revision.
jdoerfert added reviewers: lebedev.ri, hfinkel, fhahn, probinson, wristow, loladiro.
Herald added subscribers: uenoku, bollu, hiraditya.
Herald added a reviewer: sstefan1.
Herald added a reviewer: uenoku.
Herald added a project: LLVM.

We can and should remove deleted nodes from their respective SCCs. We
did not do this before and this was a potential problem even though I
couldn't locally trigger an issue. Since the `DeleteNode` would assert
if the node was not in the SCC, we know we only remove nodes from their
SCC and only once (when run on all the Attributor tests).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77855

Files:
  llvm/include/llvm/Analysis/CallGraphSCCPass.h
  llvm/lib/Analysis/CallGraphSCCPass.cpp
  llvm/lib/Transforms/Utils/CallGraphUpdater.cpp


Index: llvm/lib/Transforms/Utils/CallGraphUpdater.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CallGraphUpdater.cpp
+++ llvm/lib/Transforms/Utils/CallGraphUpdater.cpp
@@ -103,6 +103,10 @@
     DeadFunctionsInComdats.push_back(&DeadFn);
   else
     DeadFunctions.push_back(&DeadFn);
+
+  // For the old call graph we remove the function from the SCC right away.
+  if (CGSCC && !ReplacedFunctions.count(&DeadFn))
+    CGSCC->DeleteNode((*CG)[&DeadFn]);
 }
 
 void CallGraphUpdater::replaceFunctionWith(Function &OldFn, Function &NewFn) {
Index: llvm/lib/Analysis/CallGraphSCCPass.cpp
===================================================================
--- llvm/lib/Analysis/CallGraphSCCPass.cpp
+++ llvm/lib/Analysis/CallGraphSCCPass.cpp
@@ -562,6 +562,10 @@
   CGI->ReplaceNode(Old, New);
 }
 
+void CallGraphSCC::DeleteNode(CallGraphNode *Old) {
+  ReplaceNode(Old, /* New */ nullptr);
+}
+
 //===----------------------------------------------------------------------===//
 // CallGraphSCCPass Implementation
 //===----------------------------------------------------------------------===//
Index: llvm/include/llvm/Analysis/CallGraphSCCPass.h
===================================================================
--- llvm/include/llvm/Analysis/CallGraphSCCPass.h
+++ llvm/include/llvm/Analysis/CallGraphSCCPass.h
@@ -103,6 +103,10 @@
   /// Old node has been deleted, and New is to be used in its place.
   void ReplaceNode(CallGraphNode *Old, CallGraphNode *New);
 
+  /// DeleteNode - This informs the SCC and the pass manager that the specified
+  /// Old node has been deleted.
+  void DeleteNode(CallGraphNode *Old);
+
   using iterator = std::vector<CallGraphNode *>::const_iterator;
 
   iterator begin() const { return Nodes.begin(); }


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