Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1737,6 +1737,17 @@
   unsigned DstReg = DstRegOp->getReg();
   MCInst tmpInst;
 
+  bool UseAT = false;
+  unsigned ATReg = 0;
+  if (UseSrcReg && (DstReg == SrcReg)) {
+    UseAT = true;
+    // At this point we need AT to perform the expansions and we exit if it is
+    // not available.
+    ATReg = getATReg(IDLoc);
+    if (!ATReg)
+      return true;
+  }
+
   tmpInst.setLoc(IDLoc);
   // FIXME: gas has a special case for values that are 000...1111, which
   // becomes a li -1 and then a dsrl
@@ -1764,16 +1775,16 @@
     uint16_t Bits15To0 = ImmValue & 0xffff;
 
     tmpInst.setOpcode(Mips::LUi);
-    tmpInst.addOperand(MCOperand::CreateReg(DstReg));
+    tmpInst.addOperand(MCOperand::CreateReg(UseAT ? ATReg : DstReg));
     tmpInst.addOperand(MCOperand::CreateImm(Bits31To16));
     Instructions.push_back(tmpInst);
-    createLShiftOri<0>(Bits15To0, DstReg, IDLoc, Instructions);
+    createLShiftOri<0>(Bits15To0, UseAT ? ATReg : DstReg, IDLoc, Instructions);
 
     if (UseSrcReg) {
       tmpInst.clear();
       tmpInst.setOpcode(Mips::ADDu);
       tmpInst.addOperand(MCOperand::CreateReg(DstReg));
-      tmpInst.addOperand(MCOperand::CreateReg(DstReg));
+      tmpInst.addOperand(MCOperand::CreateReg(UseAT ? ATReg : DstReg));
       tmpInst.addOperand(MCOperand::CreateReg(SrcReg));
       Instructions.push_back(tmpInst);
     }
@@ -1801,17 +1812,17 @@
     uint16_t Bits15To0 = ImmValue & 0xffff;
 
     tmpInst.setOpcode(Mips::LUi);
-    tmpInst.addOperand(MCOperand::CreateReg(DstReg));
+    tmpInst.addOperand(MCOperand::CreateReg(UseAT ? ATReg : DstReg));
     tmpInst.addOperand(MCOperand::CreateImm(Bits47To32));
     Instructions.push_back(tmpInst);
-    createLShiftOri<0>(Bits31To16, DstReg, IDLoc, Instructions);
-    createLShiftOri<16>(Bits15To0, DstReg, IDLoc, Instructions);
+    createLShiftOri<0>(Bits31To16, UseAT ? ATReg : DstReg, IDLoc, Instructions);
+    createLShiftOri<16>(Bits15To0, UseAT ? ATReg : DstReg, IDLoc, Instructions);
 
     if (UseSrcReg) {
       tmpInst.clear();
       tmpInst.setOpcode(Mips::ADDu);
       tmpInst.addOperand(MCOperand::CreateReg(DstReg));
-      tmpInst.addOperand(MCOperand::CreateReg(DstReg));
+      tmpInst.addOperand(MCOperand::CreateReg(UseAT ? ATReg : DstReg));
       tmpInst.addOperand(MCOperand::CreateReg(SrcReg));
       Instructions.push_back(tmpInst);
     }
@@ -1841,26 +1852,26 @@
     uint16_t Bits15To0 = ImmValue & 0xffff;
 
     tmpInst.setOpcode(Mips::LUi);
-    tmpInst.addOperand(MCOperand::CreateReg(DstReg));
+    tmpInst.addOperand(MCOperand::CreateReg(UseAT ? ATReg : DstReg));
     tmpInst.addOperand(MCOperand::CreateImm(Bits63To48));
     Instructions.push_back(tmpInst);
-    createLShiftOri<0>(Bits47To32, DstReg, IDLoc, Instructions);
+    createLShiftOri<0>(Bits47To32, UseAT ? ATReg : DstReg, IDLoc, Instructions);
 
     // When Bits31To16 is 0, do a left shift of 32 bits instead of doing
     // two left shifts of 16 bits.
     if (Bits31To16 == 0) {
-      createLShiftOri<32>(0, DstReg, IDLoc, Instructions);
-      createLShiftOri<0>(Bits15To0, DstReg, IDLoc, Instructions);
+      createLShiftOri<32>(0, UseAT ? ATReg : DstReg, IDLoc, Instructions);
+      createLShiftOri<0>(Bits15To0, UseAT ? ATReg : DstReg, IDLoc, Instructions);
     } else {
-      createLShiftOri<16>(Bits31To16, DstReg, IDLoc, Instructions);
-      createLShiftOri<16>(Bits15To0, DstReg, IDLoc, Instructions);
+      createLShiftOri<16>(Bits31To16, UseAT ? ATReg : DstReg, IDLoc, Instructions);
+      createLShiftOri<16>(Bits15To0, UseAT ? ATReg : DstReg, IDLoc, Instructions);
     }
 
     if (UseSrcReg) {
       tmpInst.clear();
       tmpInst.setOpcode(Mips::ADDu);
       tmpInst.addOperand(MCOperand::CreateReg(DstReg));
-      tmpInst.addOperand(MCOperand::CreateReg(DstReg));
+      tmpInst.addOperand(MCOperand::CreateReg(UseAT ? ATReg : DstReg));
       tmpInst.addOperand(MCOperand::CreateReg(SrcReg));
       Instructions.push_back(tmpInst);
     }
Index: test/MC/Mips/mips-expansions.s
===================================================================
--- test/MC/Mips/mips-expansions.s
+++ test/MC/Mips/mips-expansions.s
@@ -148,6 +148,11 @@
 # CHECK:                                #   fixup A - offset: 0, value: symbol@ABS_LO, kind: fixup_Mips_LO16
 # CHECK: addu $8, $1, $8                # encoding: [0x21,0x40,0x28,0x00]
 
+# CHECK: ori  $8, $8, 20                # encoding: [0x14,0x00,0x08,0x35]
+# CHECK: lui  $1, 1                     # encoding: [0x01,0x00,0x01,0x3c]
+# CHECK: ori  $1, $1, 2                 # encoding: [0x02,0x00,0x21,0x34]
+# CHECK: addu $8, $1, $8                # encoding: [0x21,0x40,0x28,0x00]
+
 # CHECK: lui     $10, %hi(symbol)        # encoding: [A,A,0x0a,0x3c]
 # CHECK:                                 #   fixup A - offset: 0, value: symbol@ABS_HI, kind: fixup_Mips_HI16
 # CHECK: addu    $10, $10, $4            # encoding: [0x21,0x50,0x44,0x01]
@@ -221,6 +226,9 @@
     la $8, symbol-65538($8)
     la $8, symbol-0x11111($8)
 
+    la $8, 20($8)
+    la $8, 65538($8)
+
     .set noat
     lw  $t2, symbol($a0)
     .set at