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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132149 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 2bcd59f1bd8959f3fec3c2aecf0ec5b092dc4a0c..719cd264f684ddca232004826ff86161dc48d24e 100644 (file)
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -1056,10 +1056,13 @@ ReoptimizeBlock:
         !MBB->hasAddressTaken() && !MBB->isLandingPad()) {
       DEBUG(dbgs() << "\nMerging into block: " << PrevBB
                    << "From MBB: " << *MBB);
+      // Remove redundant DBG_VALUEs first.
       if (PrevBB.begin() != PrevBB.end()) {
         MachineBasicBlock::iterator PrevBBIter = PrevBB.end();
         --PrevBBIter;
         MachineBasicBlock::iterator MBBIter = MBB->begin();
+        // Check if DBG_VALUE at the end of PrevBB is identical to the 
+        // DBG_VALUE at the beginning of MBB.
         while (PrevBBIter != PrevBB.begin() && MBBIter != MBB->end()
                && PrevBBIter->isDebugValue() && MBBIter->isDebugValue()) {
           if (!MBBIter->isIdenticalTo(PrevBBIter))