diff --git a/clang/test/CodeGen/asan-globals-alias.cpp b/clang/test/CodeGen/asan-globals-alias.cpp
--- a/clang/test/CodeGen/asan-globals-alias.cpp
+++ b/clang/test/CodeGen/asan-globals-alias.cpp
@@ -36,8 +36,8 @@
 // CHECK: @__mod_joydev_ids_device_table ={{.*}} alias
 
 // CHECK-LABEL: define internal void @asan.module_ctor
-// ASAN: call void @__asan_register_globals({{.*}}, i{{32|64}} 4)
-// KASAN: call void @__asan_register_globals({{.*}}, i{{32|64}} 1)
+// ASAN: call void @__asan_register_globals({{.*}}, i{{32|64}} 5)
+// KASAN: call void @__asan_register_globals({{.*}}, i{{32|64}} 2)
 // CHECK-NEXT: ret void
 
 // CHECK-LABEL: define internal void @asan.module_dtor
diff --git a/clang/test/CodeGen/asan-globals-odr.cpp b/clang/test/CodeGen/asan-globals-odr.cpp
--- a/clang/test/CodeGen/asan-globals-odr.cpp
+++ b/clang/test/CodeGen/asan-globals-odr.cpp
@@ -24,7 +24,7 @@
 // GLOB_ALIAS_INDICATOR: @0 = internal global {{.*}} @1 to i64), {{.*}}, i64 ptrtoint (i8* [[ODR]] to i64) }]
 
 // ALIAS0-NOT: private alias
-// ALIAS1: @1 = private alias {{.*}} [[VAR]]
+// ALIAS1: @2 = private alias {{.*}} [[VAR]]
 
-// CHECK: call void @__asan_register_globals(i64 ptrtoint ([1 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 1)
-// CHECK: call void @__asan_unregister_globals(i64 ptrtoint ([1 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 1)
+// CHECK: call void @__asan_register_globals(i64 ptrtoint ([2 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 2)
+// CHECK: call void @__asan_unregister_globals(i64 ptrtoint ([2 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 2)
diff --git a/clang/test/CodeGen/asan-globals.cpp b/clang/test/CodeGen/asan-globals.cpp
--- a/clang/test/CodeGen/asan-globals.cpp
+++ b/clang/test/CodeGen/asan-globals.cpp
@@ -33,8 +33,8 @@
 // ASAN-NEXT: call void @__asan_version_mismatch_check
 // KASAN-NOT: call void @__asan_init
 // KASAN-NOT: call void @__asan_version_mismatch_check
-// ASAN-NEXT: call void @__asan_register_globals({{.*}}, i{{32|64}} 7)
-// KASAN-NEXT: call void @__asan_register_globals({{.*}}, i{{32|64}} 5)
+// ASAN-NEXT: call void @__asan_register_globals({{.*}}, i{{32|64}} 8)
+// KASAN-NEXT: call void @__asan_register_globals({{.*}}, i{{32|64}} 6)
 // CHECK-NEXT: ret void
 
 // CHECK:      define internal void @asan.module_dtor() #[[#ATTR]] {
diff --git a/clang/test/CodeGen/asan-static-odr.cpp b/clang/test/CodeGen/asan-static-odr.cpp
--- a/clang/test/CodeGen/asan-static-odr.cpp
+++ b/clang/test/CodeGen/asan-static-odr.cpp
@@ -13,5 +13,5 @@
 // CHECK-NOT: private alias
 // CHECK: [[VAR:@.*global.*]] ={{.*}} global { i32, [60 x i8] } zeroinitializer, align 32
 // CHECK: @0 = internal global {{.*}} [[VAR]] to i64), {{.*}}, i64 -1 }]
-// CHECK: call void @__asan_register_globals(i64 ptrtoint ([1 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 1)
-// CHECK: call void @__asan_unregister_globals(i64 ptrtoint ([1 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 1)
+// CHECK: call void @__asan_register_globals(i64 ptrtoint ([2 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 2)
+// CHECK: call void @__asan_unregister_globals(i64 ptrtoint ([2 x { i64, i64, i64, i64, i64, i64, i64, i64 }]* @0 to i64), i64 2)
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -2372,6 +2372,18 @@
     return false;
   }
 
+  // Create a global zero-sized array precedence before GlobalsToChange[0] so
+  // that the underflow of the it could be observable.
+  ArrayType *ZeroSizedArrayTy = ArrayType::get(IRB.getInt8Ty(), 0);
+  GlobalVariable *UnderflowObserverGV = new GlobalVariable(
+      M, ZeroSizedArrayTy, /*isConstant*/ false, GlobalVariable::PrivateLinkage,
+      ConstantArray::get(ZeroSizedArrayTy, {}), kAsanGenPrefix,
+      GlobalsToChange[0]);
+  GlobalsToChange.insert(GlobalsToChange.begin(), UnderflowObserverGV);
+
+  // Update size as we insert a dummy one.
+  n = GlobalsToChange.size();
+
   auto &DL = M.getDataLayout();
 
   // A global is described by a structure
diff --git a/llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll b/llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
--- a/llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
@@ -28,8 +28,8 @@
 ; CHECK: [[LOCDESCR:@___asan_gen_.[0-9]+]] = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* [[FILENAME]], i32 5, i32 5 }
 ; NOALIAS: @__asan_global_global = {{.*}}i64 ptrtoint ({ i32, [60 x i8] }* @global to i64){{.*}} section "asan_globals"{{.*}}, !associated
 ; NOALIAS: @__asan_global_.str = {{.*}}i64 ptrtoint ({ [14 x i8], [50 x i8] }* @{{.str|1}} to i64){{.*}} section "asan_globals"{{.*}}, !associated
-; ALIAS: @__asan_global_global = {{.*}}i64 ptrtoint ({ i32, [60 x i8] }* @0 to i64){{.*}} section "asan_globals"{{.*}}, !associated
-; ALIAS: @__asan_global_.str = {{.*}}i64 ptrtoint ({ [14 x i8], [50 x i8] }* @3 to i64){{.*}} section "asan_globals"{{.*}}, !associated
+; ALIAS: @__asan_global_global = {{.*}}i64 ptrtoint ({ i32, [60 x i8] }* @1 to i64){{.*}} section "asan_globals"{{.*}}, !associated
+; ALIAS: @__asan_global_.str = {{.*}}i64 ptrtoint ({ [14 x i8], [50 x i8] }* @4 to i64){{.*}} section "asan_globals"{{.*}}, !associated
 
 ; The metadata has to be inserted to llvm.compiler.used to avoid being stripped
 ; during LTO.