Index: lib/Target/Mips/MicroMips32r6InstrFormats.td
===================================================================
--- lib/Target/Mips/MicroMips32r6InstrFormats.td
+++ lib/Target/Mips/MicroMips32r6InstrFormats.td
@@ -15,3 +15,31 @@
   string Arch = "micromipsr6";
   string BaseOpcode = opstr;
 }
+
+class ARITH_FM_MMR6<string instr_asm, bits<10> funct> : MMR6Arch<instr_asm> {
+  bits<5> rd;
+  bits<5> rt;
+  bits<5> rs;
+
+  bits<32> Inst;
+
+  let Inst{31-26} = 0;
+  let Inst{25-21} = rt;
+  let Inst{20-16} = rs;
+  let Inst{15-11} = rd;
+  let Inst{10}    = 0;
+  let Inst{9-0}   = funct;
+}
+
+class ADDI_FM_MMR6<string instr_asm, bits<6> op> : MMR6Arch<instr_asm> {
+  bits<5>  rt;
+  bits<5>  rs;
+  bits<16> imm16;
+
+  bits<32> Inst;
+
+  let Inst{31-26} = op;
+  let Inst{25-21} = rt;
+  let Inst{20-16} = rs;
+  let Inst{15-0}  = imm16;
+}
Index: lib/Target/Mips/MicroMips32r6InstrInfo.td
===================================================================
--- lib/Target/Mips/MicroMips32r6InstrInfo.td
+++ lib/Target/Mips/MicroMips32r6InstrInfo.td
@@ -16,7 +16,9 @@
 // Instruction Encodings
 //
 //===----------------------------------------------------------------------===//
-
+class ADD_MMR6_ENC : ARITH_FM_MMR6<"add", 0x110>;
+class ADDIU_MMR6_ENC : ADDI_FM_MMR6<"addiu", 0xc>;
+class ADDU_MMR6_ENC : ARITH_FM_MMR6<"addu", 0x150>;
 class BALC_MMR6_ENC  : BRANCH_OFF26_FM<0b101101>;
 class BC_MMR6_ENC : BRANCH_OFF26_FM<0b100101>;
 
@@ -26,6 +28,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+class ADD_MMR6_DESC : ArithLogicR<"add", GPR32Opnd>;
+class ADDIU_MMR6_DESC : ArithLogicI<"addiu", simm16, GPR32Opnd>;
+class ADDU_MMR6_DESC : ArithLogicR<"addu", GPR32Opnd>;
+
 class BC_MMR6_DESC_BASE<string instr_asm, DAGOperand opnd>
     : BRANCH_DESC_BASE, MMR6Arch<instr_asm> {
   dag InOperandList = (ins opnd:$offset);
@@ -47,6 +53,9 @@
 //===----------------------------------------------------------------------===//
 
 let DecoderNamespace = "MicroMips32r6" in {
+def ADD_MMR6 : StdMMR6Rel, ADD_MMR6_DESC, ADD_MMR6_ENC, ISA_MICROMIPS32R6;
+def ADDIU_MMR6 : StdMMR6Rel, ADDIU_MMR6_DESC, ADDIU_MMR6_ENC, ISA_MICROMIPS32R6;
+def ADDU_MMR6 : StdMMR6Rel, ADDU_MMR6_DESC, ADDU_MMR6_ENC, ISA_MICROMIPS32R6;
 def BALC_MMR6 : R6MMR6Rel, BALC_MMR6_ENC, BALC_MMR6_DESC, ISA_MICROMIPS32R6;
 def BC_MMR6 : R6MMR6Rel, BC_MMR6_ENC, BC_MMR6_DESC, ISA_MICROMIPS32R6;
 }
Index: lib/Target/Mips/MipsInstrInfo.td
===================================================================
--- lib/Target/Mips/MipsInstrInfo.td
+++ lib/Target/Mips/MipsInstrInfo.td
@@ -1123,8 +1123,9 @@
 
 /// Arithmetic Instructions (ALU Immediate)
 let AdditionalPredicates = [NotInMicroMips] in {
-def ADDiu : MMRel, ArithLogicI<"addiu", simm16, GPR32Opnd, II_ADDIU, immSExt16,
-                               add>, ADDI_FM<0x9>, IsAsCheapAsAMove;
+def ADDiu : MMRel, StdMMR6Rel, ArithLogicI<"addiu", simm16, GPR32Opnd,
+                                           II_ADDIU, immSExt16, add>,
+            ADDI_FM<0x9>, IsAsCheapAsAMove;
 }
 def ADDi  : MMRel, ArithLogicI<"addi", simm16, GPR32Opnd>, ADDI_FM<0x8>,
             ISA_MIPS1_NOT_32R6_64R6;
@@ -1145,7 +1146,7 @@
 def LUi   : MMRel, LoadUpper<"lui", GPR32Opnd, uimm16>, LUI_FM;
 let AdditionalPredicates = [NotInMicroMips] in {
 /// Arithmetic Instructions (3-Operand, R-Type)
-def ADDu  : MMRel, ArithLogicR<"addu", GPR32Opnd, 1, II_ADDU, add>,
+def ADDu  : MMRel, StdMMR6Rel, ArithLogicR<"addu", GPR32Opnd, 1, II_ADDU, add>,
             ADD_FM<0, 0x21>;
 def SUBu  : MMRel, ArithLogicR<"subu", GPR32Opnd, 0, II_SUBU, sub>,
             ADD_FM<0, 0x23>;
@@ -1153,7 +1154,7 @@
 let Defs = [HI0, LO0] in
 def MUL   : MMRel, ArithLogicR<"mul", GPR32Opnd, 1, II_MUL, mul>,
             ADD_FM<0x1c, 2>, ISA_MIPS32_NOT_32R6_64R6;
-def ADD   : MMRel, ArithLogicR<"add", GPR32Opnd>, ADD_FM<0, 0x20>;
+def ADD   : MMRel, StdMMR6Rel, ArithLogicR<"add", GPR32Opnd>, ADD_FM<0, 0x20>;
 def SUB   : MMRel, ArithLogicR<"sub", GPR32Opnd>, ADD_FM<0, 0x22>;
 def SLT   : MMRel, SetCC_R<"slt", setlt, GPR32Opnd>, ADD_FM<0, 0x2a>;
 def SLTu  : MMRel, SetCC_R<"sltu", setult, GPR32Opnd>, ADD_FM<0, 0x2b>;
Index: test/MC/Disassembler/Mips/micromips32r6.txt
===================================================================
--- /dev/null
+++ test/MC/Disassembler/Mips/micromips32r6.txt
@@ -0,0 +1,11 @@
+# RUN: llvm-mc --disassemble %s -triple=mips-unknown-linux -mcpu=mips32r6 -mattr=micromips32r6 | FileCheck %s
+
+# CHECK: add $3, $4, $5
+0x00 0xa4 0x19 0x10
+
+# CHECK: addiu $3, $4, 1234
+0x30 0x64 0x04 0xd2
+
+# CHECK: addu $3, $4, $5
+0x00 0xa4 0x19 0x50
+
Index: test/MC/Mips/micromipsr6/valid.s
===================================================================
--- test/MC/Mips/micromipsr6/valid.s
+++ test/MC/Mips/micromipsr6/valid.s
@@ -1,5 +1,8 @@
 # RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips32r6 -mattr=micromips32r6 | FileCheck %s
 
   .set noat
+  add $3, $4, $5           # CHECK: add $3, $4, $5      # encoding: [0x00,0xa4,0x19,0x10]
+  addiu $3, $4, 1234       # CHECK: addiu $3, $4, 1234  # encoding: [0x30,0x64,0x04,0xd2]
+  addu $3, $4, $5          # CHECK: addu $3, $4, $5     # encoding: [0x00,0xa4,0x19,0x50]
   balc 14572256            # CHECK: balc 14572256       # encoding: [0xb4,0x37,0x96,0xb8]
   bc 14572256              # CHECK: bc 14572256         # encoding: [0x94,0x37,0x96,0xb8]