diff --git a/lib/Target/ARM64/ARM64ISelDAGToDAG.cpp b/lib/Target/ARM64/ARM64ISelDAGToDAG.cpp
index 9b235db30a3..23c45d414e2 100644
--- a/lib/Target/ARM64/ARM64ISelDAGToDAG.cpp
+++ b/lib/Target/ARM64/ARM64ISelDAGToDAG.cpp
@@ -517,6 +517,21 @@ SDNode *ARM64DAGToDAGISel::SelectMULLV64LaneV128(unsigned IntNo, SDNode *N) {
   return CurDAG->getMachineNode(SMULLOpc, SDLoc(N), N->getValueType(0), Ops);
 }
 
+/// Instructions that accept extend modifiers like UXTW expect the register
+/// being extended to be a GPR32, but the incoming DAG might be acting on a
+/// GPR64 (either via SEXT_INREG or AND). Extract the appropriate low bits if
+/// this is the case.
+static SDValue narrowIfNeeded(SelectionDAG *CurDAG, SDValue N) {
+  if (N.getValueType() == MVT::i32)
+    return N;
+
+  SDValue SubReg = CurDAG->getTargetConstant(ARM64::sub_32, MVT::i32);
+  MachineSDNode *Node = CurDAG->getMachineNode(TargetOpcode::EXTRACT_SUBREG,
+                                               SDLoc(N), MVT::i32, N, SubReg);
+  return SDValue(Node, 0);
+}
+
+
 /// SelectArithExtendedRegister - Select a "extended register" operand.  This
 /// operand folds in an extend followed by an optional left shift.
 bool ARM64DAGToDAGISel::SelectArithExtendedRegister(SDValue N, SDValue &Reg,
@@ -551,13 +566,7 @@ bool ARM64DAGToDAGISel::SelectArithExtendedRegister(SDValue N, SDValue &Reg,
   // there might not be an actual 32-bit value in the program.  We can
   // (harmlessly) synthesize one by injected an EXTRACT_SUBREG here.
   assert(Ext != ARM64_AM::UXTX && Ext != ARM64_AM::SXTX);
-  if (Reg.getValueType() == MVT::i64) {
-    SDValue SubReg = CurDAG->getTargetConstant(ARM64::sub_32, MVT::i32);
-    MachineSDNode *Node = CurDAG->getMachineNode(
-        TargetOpcode::EXTRACT_SUBREG, SDLoc(N), MVT::i32, Reg, SubReg);
-    Reg = SDValue(Node, 0);
-  }
-
+  Reg = narrowIfNeeded(CurDAG, Reg);
   Shift = CurDAG->getTargetConstant(getArithExtendImm(Ext, ShiftVal), MVT::i32);
   return isWorthFolding(N);
 }
@@ -677,7 +686,7 @@ bool ARM64DAGToDAGISel::SelectExtendedSHL(SDValue N, unsigned Size,
     if (Ext == ARM64_AM::InvalidShiftExtend)
       return false;
 
-    Offset = N.getOperand(0).getOperand(0);
+    Offset = narrowIfNeeded(CurDAG, N.getOperand(0).getOperand(0));
     SignExtend = CurDAG->getTargetConstant(Ext == ARM64_AM::SXTW, MVT::i32);
   } else {
     Offset = N.getOperand(0);
@@ -746,7 +755,7 @@ bool ARM64DAGToDAGISel::SelectAddrModeWRO(SDValue N, unsigned Size,
   if (IsExtendedRegisterWorthFolding &&
       (Ext = getExtendTypeForNode(LHS, true)) != ARM64_AM::InvalidShiftExtend) {
     Base = RHS;
-    Offset = LHS.getOperand(0);
+    Offset = narrowIfNeeded(CurDAG, LHS.getOperand(0));
     SignExtend = CurDAG->getTargetConstant(Ext == ARM64_AM::SXTW, MVT::i32);
     if (isWorthFolding(LHS))
       return true;
@@ -756,7 +765,7 @@ bool ARM64DAGToDAGISel::SelectAddrModeWRO(SDValue N, unsigned Size,
   if (IsExtendedRegisterWorthFolding &&
       (Ext = getExtendTypeForNode(RHS, true)) != ARM64_AM::InvalidShiftExtend) {
     Base = LHS;
-    Offset = RHS.getOperand(0);
+    Offset = narrowIfNeeded(CurDAG, RHS.getOperand(0));
     SignExtend = CurDAG->getTargetConstant(Ext == ARM64_AM::SXTW, MVT::i32);
     if (isWorthFolding(RHS))
       return true;
diff --git a/test/CodeGen/ARM64/register-offset-addressing.ll b/test/CodeGen/ARM64/register-offset-addressing.ll
index c27360257cd..045712bea6a 100644
--- a/test/CodeGen/ARM64/register-offset-addressing.ll
+++ b/test/CodeGen/ARM64/register-offset-addressing.ll
@@ -1,7 +1,7 @@
 ; RUN: llc < %s -mtriple=arm64-apple-darwin | FileCheck %s
 
-define i8 @t1(i16* %a, i64 %b) {
-; CHECK: t1
+define i8 @test_64bit_add(i16* %a, i64 %b) {
+; CHECK-LABEL: test_64bit_add:
 ; CHECK: lsl [[REG:x[0-9]+]], x1, #1
 ; CHECK: ldrb w0, [x0, [[REG]]]
 ; CHECK: ret
@@ -10,3 +10,136 @@ define i8 @t1(i16* %a, i64 %b) {
   %tmp3 = trunc i16 %tmp2 to i8
   ret i8 %tmp3
 }
+
+; These tests are trying to form SEXT and ZEXT operations that never leave i64
+; space, to make sure LLVM can adapt the offset register correctly.
+define void @ldst_8bit(i8* %base, i64 %offset) minsize {
+; CHECK-LABEL: ldst_8bit:
+
+   %off32.sext.tmp = shl i64 %offset, 32
+   %off32.sext = ashr i64 %off32.sext.tmp, 32
+   %addr8_sxtw = getelementptr i8* %base, i64 %off32.sext
+   %val8_sxtw = load volatile i8* %addr8_sxtw
+   %val32_signed = sext i8 %val8_sxtw to i32
+   store volatile i32 %val32_signed, i32* @var_32bit
+; CHECK: ldrsb {{w[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, sxtw]
+
+  %addrint_uxtw = ptrtoint i8* %base to i64
+  %offset_uxtw = and i64 %offset, 4294967295
+  %addrint1_uxtw = add i64 %addrint_uxtw, %offset_uxtw
+  %addr_uxtw = inttoptr i64 %addrint1_uxtw to i8*
+  %val8_uxtw = load volatile i8* %addr_uxtw
+  %newval8 = add i8 %val8_uxtw, 1
+  store volatile i8 %newval8, i8* @var_8bit
+; CHECK: ldrb {{w[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw]
+
+   ret void
+}
+
+
+define void @ldst_16bit(i16* %base, i64 %offset) minsize {
+; CHECK-LABEL: ldst_16bit:
+
+  %addrint_uxtw = ptrtoint i16* %base to i64
+  %offset_uxtw = and i64 %offset, 4294967295
+  %addrint1_uxtw = add i64 %addrint_uxtw, %offset_uxtw
+  %addr_uxtw = inttoptr i64 %addrint1_uxtw to i16*
+  %val8_uxtw = load volatile i16* %addr_uxtw
+  %newval8 = add i16 %val8_uxtw, 1
+  store volatile i16 %newval8, i16* @var_16bit
+; CHECK: ldrh {{w[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw]
+
+  %base_sxtw = ptrtoint i16* %base to i64
+  %offset_sxtw.tmp = shl i64 %offset, 32
+  %offset_sxtw = ashr i64 %offset_sxtw.tmp, 32
+  %addrint_sxtw = add i64 %base_sxtw, %offset_sxtw
+  %addr_sxtw = inttoptr i64 %addrint_sxtw to i16*
+  %val16_sxtw = load volatile i16* %addr_sxtw
+  %val64_signed = sext i16 %val16_sxtw to i64
+  store volatile i64 %val64_signed, i64* @var_64bit
+; CHECK: ldrsh {{x[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, sxtw]
+
+
+  %base_uxtwN = ptrtoint i16* %base to i64
+  %offset_uxtwN = and i64 %offset, 4294967295
+  %offset2_uxtwN = shl i64 %offset_uxtwN, 1
+  %addrint_uxtwN = add i64 %base_uxtwN, %offset2_uxtwN
+  %addr_uxtwN = inttoptr i64 %addrint_uxtwN to i16*
+  %val32 = load volatile i32* @var_32bit
+  %val16_trunc32 = trunc i32 %val32 to i16
+  store volatile i16 %val16_trunc32, i16* %addr_uxtwN
+; CHECK: strh {{w[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw #1]
+   ret void
+}
+
+define void @ldst_32bit(i32* %base, i64 %offset) minsize {
+; CHECK-LABEL: ldst_32bit:
+
+  %addrint_uxtw = ptrtoint i32* %base to i64
+  %offset_uxtw = and i64 %offset, 4294967295
+  %addrint1_uxtw = add i64 %addrint_uxtw, %offset_uxtw
+  %addr_uxtw = inttoptr i64 %addrint1_uxtw to i32*
+  %val32_uxtw = load volatile i32* %addr_uxtw
+  %newval32 = add i32 %val32_uxtw, 1
+  store volatile i32 %newval32, i32* @var_32bit
+; CHECK: ldr {{w[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw]
+
+  %base_sxtw = ptrtoint i32* %base to i64
+  %offset_sxtw.tmp = shl i64 %offset, 32
+  %offset_sxtw = ashr i64 %offset_sxtw.tmp, 32
+  %addrint_sxtw = add i64 %base_sxtw, %offset_sxtw
+  %addr_sxtw = inttoptr i64 %addrint_sxtw to i32*
+  %val32_sxtw = load volatile i32* %addr_sxtw
+  %val64_signed = sext i32 %val32_sxtw to i64
+  store volatile i64 %val64_signed, i64* @var_64bit
+; CHECK: ldrsw {{x[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, sxtw]
+
+
+  %base_uxtwN = ptrtoint i32* %base to i64
+  %offset_uxtwN = and i64 %offset, 4294967295
+  %offset2_uxtwN = shl i64 %offset_uxtwN, 2
+  %addrint_uxtwN = add i64 %base_uxtwN, %offset2_uxtwN
+  %addr_uxtwN = inttoptr i64 %addrint_uxtwN to i32*
+  %val32 = load volatile i32* @var_32bit
+  store volatile i32 %val32, i32* %addr_uxtwN
+; CHECK: str {{w[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw #2]
+   ret void
+}
+
+define void @ldst_64bit(i64* %base, i64 %offset) minsize {
+; CHECK-LABEL: ldst_64bit:
+
+  %addrint_uxtw = ptrtoint i64* %base to i64
+  %offset_uxtw = and i64 %offset, 4294967295
+  %addrint1_uxtw = add i64 %addrint_uxtw, %offset_uxtw
+  %addr_uxtw = inttoptr i64 %addrint1_uxtw to i64*
+  %val64_uxtw = load volatile i64* %addr_uxtw
+  %newval8 = add i64 %val64_uxtw, 1
+  store volatile i64 %newval8, i64* @var_64bit
+; CHECK: ldr {{x[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw]
+
+  %base_sxtw = ptrtoint i64* %base to i64
+  %offset_sxtw.tmp = shl i64 %offset, 32
+  %offset_sxtw = ashr i64 %offset_sxtw.tmp, 32
+  %addrint_sxtw = add i64 %base_sxtw, %offset_sxtw
+  %addr_sxtw = inttoptr i64 %addrint_sxtw to i64*
+  %val64_sxtw = load volatile i64* %addr_sxtw
+  store volatile i64 %val64_sxtw, i64* @var_64bit
+; CHECK: ldr {{x[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, sxtw]
+
+
+  %base_uxtwN = ptrtoint i64* %base to i64
+  %offset_uxtwN = and i64 %offset, 4294967295
+  %offset2_uxtwN = shl i64 %offset_uxtwN, 3
+  %addrint_uxtwN = add i64 %base_uxtwN, %offset2_uxtwN
+  %addr_uxtwN = inttoptr i64 %addrint_uxtwN to i64*
+  %val64 = load volatile i64* @var_64bit
+  store volatile i64 %val64, i64* %addr_uxtwN
+; CHECK: str {{x[0-9]+}}, [{{x[0-9]+}}, {{w[0-9]+}}, uxtw #3]
+   ret void
+}
+
+@var_8bit = global i8 0
+@var_16bit = global i16 0
+@var_32bit = global i32 0
+@var_64bit = global i64 0