Index: include/llvm/IR/GlobalAlias.h
===================================================================
--- include/llvm/IR/GlobalAlias.h
+++ include/llvm/IR/GlobalAlias.h
@@ -83,7 +83,8 @@
 
   static bool isValidLinkage(LinkageTypes L) {
     return isExternalLinkage(L) || isLocalLinkage(L) ||
-      isWeakLinkage(L) || isLinkOnceLinkage(L);
+      isWeakLinkage(L) || isLinkOnceLinkage(L) || 
+      isCommonLinkage(L);
   }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1330,12 +1330,14 @@
                                           const GlobalIndirectSymbol& GIS) {
   MCSymbol *Name = getSymbol(&GIS);
 
-  if (GIS.hasExternalLinkage() || !MAI->getWeakRefDirective())
+  if (GIS.hasExternalLinkage() || GIS.hasCommonLinkage() ||
+      !MAI->getWeakRefDirective())
     OutStreamer->EmitSymbolAttribute(Name, MCSA_Global);
   else if (GIS.hasWeakLinkage() || GIS.hasLinkOnceLinkage())
     OutStreamer->EmitSymbolAttribute(Name, MCSA_WeakReference);
   else
-    assert(GIS.hasLocalLinkage() && "Invalid alias or ifunc linkage");
+    assert((GIS.hasLocalLinkage()) &&
+           "Invalid alias or ifunc linkage");
 
   // Set the symbol type to function if the alias has a function type.
   // This affects codegen when the aliasee is not a function.
Index: lib/CodeGen/GlobalMerge.cpp
===================================================================
--- lib/CodeGen/GlobalMerge.cpp
+++ lib/CodeGen/GlobalMerge.cpp
@@ -616,8 +616,8 @@
     if (TM && !TM->shouldAssumeDSOLocal(M, &GV))
       continue;
 
-    if (!(MergeExternalGlobals && GV.hasExternalLinkage()) &&
-        !GV.hasInternalLinkage())
+    if (!(MergeExternalGlobals && GV.hasExternalLinkage())&&
+        !GV.hasInternalLinkage() && !GV.hasCommonLinkage())
       continue;
 
     PointerType *PT = dyn_cast<PointerType>(GV.getType());
Index: test/CodeGen/AArch64/global_merge_ac6_aarch64.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AArch64/global_merge_ac6_aarch64.ll
@@ -0,0 +1,33 @@
+;RUN: llc -O3 %s -o - -verify-machineinstrs | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-arm-none-eabi"
+
+@global0 = common dso_local local_unnamed_addr global i32 0, align 4
+@global1 = common dso_local local_unnamed_addr global i32 0, align 4
+
+; Function Attrs: norecurse nounwind readonly
+;CHECK-LABEL: @func
+;CHECK: adrp
+;CHECK-NEXT: add
+;CHECK-NEXT: ldp
+;CHECK-NEXT: add
+;CHECK-NEXT: ret
+define dso_local i32 @func() local_unnamed_addr #0 {
+  %1 = load i32, i32* @global0, align 4, !tbaa !2
+  %2 = load i32, i32* @global1, align 4, !tbaa !2
+  %3 = add nsw i32 %2, %1
+  ret i32 %3
+}
+
+attributes #0 = { norecurse nounwind readonly "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+neon" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0}
+!llvm.ident = !{!1}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{!"clang version 9.0.0 (https://git.llvm.org/git/clang.git/ 112a7a3c34df3dc506b52cd89e155287cdbcea55) (https://git.llvm.org/git/llvm.git/ feeb3cebe7a586a8e1b12735024389dd8d3bab53)"}
+!2 = !{!3, !3, i64 0}
+!3 = !{!"int", !4, i64 0}
+!4 = !{!"omnipotent char", !5, i64 0}
+!5 = !{!"Simple C/C++ TBAA"}