Index: lib/Target/Mips/MipsISelLowering.cpp
===================================================================
--- lib/Target/Mips/MipsISelLowering.cpp
+++ lib/Target/Mips/MipsISelLowering.cpp
@@ -1416,6 +1416,9 @@
   MachineFunction *MF = BB->getParent();
   MachineRegisterInfo &RegInfo = MF->getRegInfo();
   const TargetRegisterClass *RC = getRegClassFor(MVT::i32);
+  bool ArePtrs64bit = ABI.ArePtrs64bit();
+  const TargetRegisterClass *RCp =
+    getRegClassFor(ArePtrs64bit ? MVT::i64 : MVT::i32);
   const TargetInstrInfo *TII = Subtarget.getInstrInfo();
   DebugLoc DL = MI->getDebugLoc();
 
@@ -1424,7 +1427,7 @@
   unsigned CmpVal  = MI->getOperand(2).getReg();
   unsigned NewVal  = MI->getOperand(3).getReg();
 
-  unsigned AlignedAddr = RegInfo.createVirtualRegister(RC);
+  unsigned AlignedAddr = RegInfo.createVirtualRegister(RCp);
   unsigned ShiftAmt = RegInfo.createVirtualRegister(RC);
   unsigned Mask = RegInfo.createVirtualRegister(RC);
   unsigned Mask2 = RegInfo.createVirtualRegister(RC);
@@ -1432,7 +1435,7 @@
   unsigned OldVal = RegInfo.createVirtualRegister(RC);
   unsigned MaskedOldVal0 = RegInfo.createVirtualRegister(RC);
   unsigned ShiftedNewVal = RegInfo.createVirtualRegister(RC);
-  unsigned MaskLSB2 = RegInfo.createVirtualRegister(RC);
+  unsigned MaskLSB2 = RegInfo.createVirtualRegister(RCp);
   unsigned PtrLSB2 = RegInfo.createVirtualRegister(RC);
   unsigned MaskUpper = RegInfo.createVirtualRegister(RC);
   unsigned MaskedCmpVal = RegInfo.createVirtualRegister(RC);
@@ -1471,6 +1474,7 @@
   //    addiu   masklsb2,$0,-4                # 0xfffffffc
   //    and     alignedaddr,ptr,masklsb2
   //    andi    ptrlsb2,ptr,3
+  //    xori    ptrlsb2,ptrlsb2,3              # Only for BE
   //    sll     shiftamt,ptrlsb2,3
   //    ori     maskupper,$0,255               # 0xff
   //    sll     mask,maskupper,shiftamt
@@ -1480,11 +1484,15 @@
   //    andi    maskednewval,newval,255
   //    sll     shiftednewval,maskednewval,shiftamt
   int64_t MaskImm = (Size == 1) ? 255 : 65535;
-  BuildMI(BB, DL, TII->get(Mips::ADDiu), MaskLSB2)
-    .addReg(Mips::ZERO).addImm(-4);
-  BuildMI(BB, DL, TII->get(Mips::AND), AlignedAddr)
+  BuildMI(BB, DL, TII->get(ArePtrs64bit ? Mips::DADDiu : Mips::ADDiu), MaskLSB2)
+    .addReg(ABI.GetNullPtr()).addImm(-4);
+  BuildMI(BB, DL, TII->get(ArePtrs64bit ? Mips::AND64 : Mips::AND), AlignedAddr)
     .addReg(Ptr).addReg(MaskLSB2);
-  BuildMI(BB, DL, TII->get(Mips::ANDi), PtrLSB2).addReg(Ptr).addImm(3);
+  if (ArePtrs64bit)
+    BuildMI(BB, DL, TII->get(Mips::ANDi), PtrLSB2)
+      .addReg(Ptr, 0, Mips::sub_32) .addImm(3);
+  else
+    BuildMI(BB, DL, TII->get(Mips::ANDi), PtrLSB2).addReg(Ptr).addImm(3);
   if (Subtarget.isLittle()) {
     BuildMI(BB, DL, TII->get(Mips::SLL), ShiftAmt).addReg(PtrLSB2).addImm(3);
   } else {
Index: test/CodeGen/Mips/atomicCmpSwapPW.ll
===================================================================
--- /dev/null
+++ test/CodeGen/Mips/atomicCmpSwapPW.ll
@@ -0,0 +1,11 @@
+; RUN: llc -O0 -march=mips64el -mcpu=mips64r2 -target-abi=n64 < %s -filetype=asm -o - \
+; RUN:   | FileCheck %s
+
+; CHECK: ld $[[R0:[0-9]+]]
+; CHECK: ll ${{[0-9]+}}, 0($[[R0]])
+
+define {i16, i1} @foo(i16* %addr, i16 signext %r, i16 zeroext %new) {
+  %res = cmpxchg i16* %addr, i16 %r, i16 %new seq_cst seq_cst
+  ret {i16, i1} %res
+}
+