Index: llvm/trunk/lib/CodeGen/BranchFolding.h
===================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.h
+++ llvm/trunk/lib/CodeGen/BranchFolding.h
@@ -153,6 +153,7 @@
                                    MachineBasicBlock *SuccBB,
                                    unsigned maxCommonTailLength,
                                    unsigned &commonTailIndex);
+    void MergeCommonTailDebugLocs(unsigned commonTailIndex);
 
     bool OptimizeBranches(MachineFunction &MF);
     bool OptimizeBlock(MachineBasicBlock *MBB);
Index: llvm/trunk/lib/CodeGen/BranchFolding.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp
@@ -32,6 +32,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Function.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -753,6 +754,45 @@
   return true;
 }
 
+/// MergeCommonTailDebugLocs - Create merged DebugLocs of identical instructions
+/// across SameTails and assign it to the instruction in common tail.
+void BranchFolder::MergeCommonTailDebugLocs(unsigned commonTailIndex) {
+  MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
+
+  std::vector<MachineBasicBlock::iterator> NextCommonInsts(SameTails.size());
+  for (unsigned int i = 0 ; i != SameTails.size() ; ++i) {
+    if (i != commonTailIndex)
+      NextCommonInsts[i] = SameTails[i].getTailStartPos();
+    else {
+      assert(SameTails[i].getTailStartPos() == MBB->begin() &&
+          "MBB is not a common tail only block");
+    }
+  }
+
+  for (auto &MI : *MBB) {
+    if (MI.isDebugValue())
+      continue;
+    DebugLoc DL = MI.getDebugLoc();
+    for (unsigned int i = 0 ; i < NextCommonInsts.size() ; i++) {
+      if (i == commonTailIndex)
+        continue;
+
+      auto &Pos = NextCommonInsts[i];
+      assert(Pos != SameTails[i].getBlock()->end() &&
+          "Reached BB end within common tail");
+      while (Pos->isDebugValue()) {
+        ++Pos;
+        assert(Pos != SameTails[i].getBlock()->end() &&
+            "Reached BB end within common tail");
+      }
+      assert(MI.isIdenticalTo(*Pos) && "Expected matching MIIs!");
+      DL = DILocation::getMergedLocation(DL, Pos->getDebugLoc());
+      NextCommonInsts[i] = ++Pos;
+    }
+    MI.setDebugLoc(DL);
+  }
+}
+
 static void
 mergeOperations(MachineBasicBlock::iterator MBBIStartPos,
                 MachineBasicBlock &MBBCommon) {
@@ -905,10 +945,8 @@
     // Recompute common tail MBB's edge weights and block frequency.
     setCommonTailEdgeWeights(*MBB);
 
-    // Remove the original debug location from the common tail.
-    for (auto &MI : *MBB)
-      if (!MI.isDebugValue())
-        MI.setDebugLoc(DebugLoc());
+    // Merge debug locations across identical instructions for common tail
+    MergeCommonTailDebugLocs(commonTailIndex);
 
     // MBB is common tail.  Adjust all other BB's to jump to this one.
     // Traversal must be forwards so erases work.
Index: llvm/trunk/test/CodeGen/X86/tail-merge-debugloc.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/tail-merge-debugloc.ll
+++ llvm/trunk/test/CodeGen/X86/tail-merge-debugloc.ll
@@ -0,0 +1,42 @@
+; RUN: llc -stop-after=branch-folder < %s | FileCheck %s
+;
+; bb2 and bb3 in the IR below will be tail-merged into a single basic block.
+; As br instructions in bb2 and bb3 have the same debug location, make sure that
+; the branch instruction in the merged basic block still maintains the debug 
+; location info.
+; 
+; CHECK:      [[DLOC:![0-9]+]] = !DILocation(line: 2, column: 2, scope: !{{[0-9]+}})
+; CHECK:      TEST64rr{{.*}}%rsi, %rsi, implicit-def %eflags
+; CHECK-NEXT: JNE_1{{.*}}, debug-location [[DLOC]]
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @foo(i1 %b, i8* %p) {
+bb1: 
+  br i1 %b, label %bb2, label %bb3
+
+bb2:
+  %a1 = icmp eq i8* %p, null
+  br i1 %a1, label %bb4, label %bb5, !dbg !6
+  
+bb3:
+  %a2 = icmp eq i8* %p, null
+  br i1 %a2, label %bb4, label %bb5, !dbg !6
+
+bb4:
+  ret i32 1
+
+bb5:
+  ret i32 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1)
+!1 = !DIFile(filename: "foo.c", directory: "b/")
+!2 = !{i32 2, !"Dwarf Version", i32 4}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 3, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
+!5 = distinct !DILexicalBlock(scope: !4, file: !1, line: 1, column: 1)
+!6 = !DILocation(line: 2, column: 2, scope: !5)