Fix LDV InstrRefBasedImpl to not crash when encountering unreachable MBBs.

The testcase was delta-reduced from an LTO build with sanitizer
coverage and the MIR tail duplication pass caused a machine basic
block to become unreachable in MIR. This caused the MBB to be invisible
to the reverse post-order traversal used to initialize the MBB <->
RPONumber lookup tables.

rdar://97226240

Differential Revision: https://reviews.llvm.org/D130999

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index 191596d..db4ab3c 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -2933,12 +2933,17 @@ void InstrRefBasedLDV::initialSetup(MachineFunction &MF) {
   // Compute mappings of block <=> RPO order.
   ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
   unsigned int RPONumber = 0;
-  for (MachineBasicBlock *MBB : RPOT) {
+  auto processMBB = [&](MachineBasicBlock *MBB) {
     OrderToBB[RPONumber] = MBB;
     BBToOrder[MBB] = RPONumber;
     BBNumToRPO[MBB->getNumber()] = RPONumber;
     ++RPONumber;
-  }
+  };
+  for (MachineBasicBlock *MBB : RPOT)
+    processMBB(MBB);
+  for (MachineBasicBlock &MBB : MF)
+    if (BBToOrder.find(&MBB) == BBToOrder.end())
+      processMBB(&MBB);
 
   // Order value substitutions by their "source" operand pair, for quick lookup.
   llvm::sort(MF.DebugValueSubstitutions);