[DebugInfo] Fix bug in LiveDebugVariables.

In lib/CodeGen/LiveDebugVariables.cpp, it uses std::prev(MBBI) to
get DebugValue's SlotIndex. However, the previous instruction may be
also a debug instruction. It could not use a debug instruction to query
SlotIndex in mi2iMap.

Scan all debug instructions and use the first debug instruction to query
SlotIndex for following debug instructions. Only handle DBG_VALUE in
handleDebugValue().

Differential Revision: https://reviews.llvm.org/D50621

llvm-svn: 341446

1 files changed, 10 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugVariables.cpp b/llvm/lib/CodeGen/LiveDebugVariables.cpp
index b258a0e..4c002d4 100644
--- a/llvm/lib/CodeGen/LiveDebugVariables.cpp
+++ b/llvm/lib/CodeGen/LiveDebugVariables.cpp
@@ -578,23 +578,28 @@ bool LDVImpl::collectDebugValues(MachineFunction &mf) {
     MachineBasicBlock *MBB = &*MFI;
     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
          MBBI != MBBE;) {
-      if (!MBBI->isDebugValue()) {
+      // Use the first debug instruction in the sequence to get a SlotIndex
+      // for following consecutive debug instructions.
+      if (!MBBI->isDebugInstr()) {
         ++MBBI;
         continue;
       }
-      // DBG_VALUE has no slot index, use the previous instruction instead.
+      // Debug instructions has no slot index. Use the previous
+      // non-debug instruction's SlotIndex as its SlotIndex.
       SlotIndex Idx =
           MBBI == MBB->begin()
               ? LIS->getMBBStartIdx(MBB)
               : LIS->getInstructionIndex(*std::prev(MBBI)).getRegSlot();
-      // Handle consecutive DBG_VALUE instructions with the same slot index.
+      // Handle consecutive debug instructions with the same slot index.
       do {
-        if (handleDebugValue(*MBBI, Idx)) {
+        // Only handle DBG_VALUE in handleDebugValue(). Skip all other
+        // kinds of debug instructions.
+        if (MBBI->isDebugValue() && handleDebugValue(*MBBI, Idx)) {
           MBBI = MBB->erase(MBBI);
           Changed = true;
         } else
           ++MBBI;
-      } while (MBBI != MBBE && MBBI->isDebugValue());
+      } while (MBBI != MBBE && MBBI->isDebugInstr());
     }
   }
   return Changed;