Index: lib/Transforms/IPO/ConstantMerge.cpp
===================================================================
--- lib/Transforms/IPO/ConstantMerge.cpp
+++ lib/Transforms/IPO/ConstantMerge.cpp
@@ -60,6 +60,23 @@
   return A.hasGlobalUnnamedAddr();
 }
 
+static bool hasMetadataOtherThanDebugLoc(const GlobalVariable *GV) {
+  SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
+  GV->getAllMetadata(MDs);
+  for (const auto &V : MDs)
+    if (V.first != LLVMContext::MD_dbg)
+      return true;
+  return false;
+}
+
+static void copyDebugLocMetadata(const GlobalVariable *From,
+                                 GlobalVariable *To) {
+  SmallVector<DIGlobalVariableExpression *, 1> MDs;
+  From->getDebugInfo(MDs);
+  for (auto MD : MDs)
+    To->addDebugInfo(MD);
+}
+
 static unsigned getAlignment(GlobalVariable *GV) {
   unsigned Align = GV->getAlignment();
   if (Align)
@@ -113,6 +130,10 @@
       if (GV->isWeakForLinker())
         continue;
 
+      // Don't touch globals with metadata other then !dbg.
+      if (hasMetadataOtherThanDebugLoc(GV))
+        continue;
+
       Constant *Init = GV->getInitializer();
 
       // Check to see if the initializer is already known.
@@ -155,6 +176,9 @@
       if (!Slot->hasGlobalUnnamedAddr() && !GV->hasGlobalUnnamedAddr())
         continue;
 
+      if (hasMetadataOtherThanDebugLoc(GV))
+        continue;
+
       if (!GV->hasGlobalUnnamedAddr())
         Slot->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
 
@@ -178,6 +202,8 @@
                      getAlignment(Replacements[i].second)));
       }
 
+      copyDebugLocMetadata(Replacements[i].first, Replacements[i].second);
+
       // Eliminate any uses of the dead global.
       Replacements[i].first->replaceAllUsesWith(Replacements[i].second);
 
Index: test/Transforms/ConstantMerge/dont-merge.ll
===================================================================
--- test/Transforms/ConstantMerge/dont-merge.ll
+++ test/Transforms/ConstantMerge/dont-merge.ll
@@ -42,3 +42,41 @@
   call void asm sideeffect "T3A, T3B",""() ; invisible use of T3A and T3B
   ret void
 }
+
+; Don't merge constants with !type annotations.
+
+@T4A1 = internal constant i32 2, !type !0
+@T4A2 = internal unnamed_addr constant i32 2, !type !1
+
+@T4B1 = internal constant i32 3, !type !0
+@T4B2 = internal unnamed_addr constant i32 3, !type !0
+
+@T4C1 = internal constant i32 4, !type !0
+@T4C2 = unnamed_addr constant i32 4
+
+@T4D1 = unnamed_addr constant i32 5, !type !0
+@T4D2 = internal constant i32 5
+
+!0 = !{i64 0, !"typeinfo name for A"}
+!1 = !{i64 0, !"typeinfo name for B"}
+
+; CHECK: @T4A1
+; CHECK: @T4A2
+; CHECK: @T4B1
+; CHECK: @T4B2
+; CHECK: @T4C1
+; CHECK: @T4C2
+; CHECK: @T4D1
+; CHECK: @T4D2
+
+define void @test4(i32** %P1, i32** %P2, i32** %P3, i32** %P4, i32** %P5, i32** %P6, i32** %P7, i32** %P8) {
+        store i32* @T4A1, i32** %P1
+        store i32* @T4A2, i32** %P2
+        store i32* @T4B1, i32** %P3
+        store i32* @T4B2, i32** %P4
+        store i32* @T4C1, i32** %P5
+        store i32* @T4C2, i32** %P6
+        store i32* @T4D1, i32** %P7
+        store i32* @T4D2, i32** %P8
+        ret void
+}
Index: test/Transforms/ConstantMerge/merge-dbg.ll
===================================================================
--- /dev/null
+++ test/Transforms/ConstantMerge/merge-dbg.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -constmerge -S | FileCheck %s
+
+; CHECK: = constant i32 1, !dbg [[A:![0-9]+]], !dbg [[B:![0-9]+]]
+@a = internal constant i32 1, !dbg !0
+@b = unnamed_addr constant i32 1, !dbg !9
+
+define void @test1(i32** %P1, i32** %P2) {
+  store i32* @a, i32** %P1
+  store i32* @b, i32** %P2
+  ret void
+}
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8}
+
+; CHECK: [[A]] = !DIGlobalVariableExpression(var: [[VA:![0-9]+]])
+; CHECK: [[VA]] = distinct !DIGlobalVariable(name: "y"
+; CHECK: [[B]] = !DIGlobalVariableExpression(var: [[VB:![0-9]+]])
+; CHECK: [[VB]] = distinct !DIGlobalVariable(name: "x"
+
+!0 = !DIGlobalVariableExpression(var: !1)
+!1 = distinct !DIGlobalVariable(name: "x", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang version 5.0.0 (trunk 297227) (llvm/trunk 297234)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "1.cc", directory: "/build")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+
+!9 = !DIGlobalVariableExpression(var: !10)
+!10 = distinct !DIGlobalVariable(name: "y", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)