[PATCH] D90498: Fix the compilation assertion due to unreachable BB pruning not deleting the associated BB from the jump tables

[Victor Huang via Phabricator via llvm-commits]

NeHuang created this revision.
NeHuang added reviewers: cperfetto, nemanjai, madscientist159, lei, power-llvm-team, hfinkel.
NeHuang added a project: LLVM.
Herald added subscribers: llvm-commits, hiraditya.
NeHuang requested review of this revision.

We encountered the same failure as https://reviews.llvm.org/D22435. Original bug tracked in https://bugs.llvm.org/show_bug.cgi?id=28102 
@cperfetto provided a potential solution to remove the unreachable MBBs reference in the jump table. (Comment 27 and Comment 28)

We have confirmed the assertion issue fixed with this patch.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D90498

Files:
  llvm/include/llvm/CodeGen/MachineJumpTableInfo.h
  llvm/lib/CodeGen/MachineFunction.cpp


Index: llvm/lib/CodeGen/MachineFunction.cpp
===================================================================
--- llvm/lib/CodeGen/MachineFunction.cpp
+++ llvm/lib/CodeGen/MachineFunction.cpp
@@ -420,6 +420,9 @@
 void
 MachineFunction::DeleteMachineBasicBlock(MachineBasicBlock *MBB) {
   assert(MBB->getParent() == this && "MBB parent mismatch!");
+  // Clean up any references to MBB in jump tables before deleting it
+  if (JumpTableInfo)
+    JumpTableInfo->RemoveMBBFromJumpTables(MBB);
   MBB->~MachineBasicBlock();
   BasicBlockRecycler.Deallocate(Allocator, MBB);
 }
@@ -1047,6 +1050,17 @@
   return MadeChange;
 }
 
+/// If MBB is present in any jump tables, remove it
+bool MachineJumpTableInfo::RemoveMBBFromJumpTables(MachineBasicBlock *MBB) {
+  bool MadeChange = false;
+  for (MachineJumpTableEntry &JTE : JumpTables) {
+    auto removeBeginItr = std::remove(JTE.MBBs.begin(), JTE.MBBs.end(), MBB);
+    MadeChange |= (removeBeginItr != JTE.MBBs.end());
+    JTE.MBBs.erase(removeBeginItr, JTE.MBBs.end());
+  }
+  return MadeChange;
+}
+
 /// If Old is a target of the jump tables, update the jump table to branch to
 /// New instead.
 bool MachineJumpTableInfo::ReplaceMBBInJumpTable(unsigned Idx,
Index: llvm/include/llvm/CodeGen/MachineJumpTableInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineJumpTableInfo.h
+++ llvm/include/llvm/CodeGen/MachineJumpTableInfo.h
@@ -106,6 +106,9 @@
     JumpTables[Idx].MBBs.clear();
   }
 
+  /// RemoveMBBFromJumpTables - If MBB is present in any jump tables, remove it
+  bool RemoveMBBFromJumpTables(MachineBasicBlock *MBB);
+
   /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
   /// the jump tables to branch to New instead.
   bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);


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