Index: lib/Target/Mips/Mips32r6InstrFormats.td
===================================================================
--- lib/Target/Mips/Mips32r6InstrFormats.td
+++ lib/Target/Mips/Mips32r6InstrFormats.td
@@ -47,8 +47,10 @@
 class OPCODE6<bits<6> Val> {
   bits<6> Value = Val;
 }
-def OPCODE6_ALIGN  : OPCODE6<0b100000>;
-def OPCODE6_DALIGN : OPCODE6<0b100100>;
+def OPCODE6_ALIGN    : OPCODE6<0b100000>;
+def OPCODE6_DALIGN   : OPCODE6<0b100100>;
+def OPCODE6_BITSWAP  : OPCODE6<0b100000>;
+def OPCODE6_DBITSWAP : OPCODE6<0b100100>;
 
 class FIELD_FMT<bits<5> Val> {
   bits<5> Value = Val;
@@ -118,6 +120,20 @@
   let Inst{18-0} = imm;
 }
 
+class SPECIAL3_2R_FM<OPCODE6 Operation> : MipsR6Inst {
+  bits<5> rd;
+  bits<5> rt;
+
+  bits<32> Inst;
+
+  let Inst{31-26} = OPGROUP_SPECIAL3.Value;
+  let Inst{25-21} = 0b00000;
+  let Inst{20-16} = rt;
+  let Inst{15-11} = rd;
+  let Inst{10-6}  = 0b00000;
+  let Inst{5-0}   = Operation.Value;
+}
+
 class SPECIAL_3R_FM<bits<5> mulop, bits<6> funct> : MipsR6Inst {
   bits<5> rd;
   bits<5> rs;
Index: lib/Target/Mips/Mips32r6InstrInfo.td
===================================================================
--- lib/Target/Mips/Mips32r6InstrInfo.td
+++ lib/Target/Mips/Mips32r6InstrInfo.td
@@ -63,6 +63,7 @@
 class ALUIPC_ENC : PCREL16_FM<OPCODE5_ALUIPC>;
 class AUI_ENC    : AUI_FM;
 class AUIPC_ENC  : PCREL16_FM<OPCODE5_AUIPC>;
+class BITSWAP_ENC : SPECIAL3_2R_FM<OPCODE6_BITSWAP>;
 class DIV_ENC    : SPECIAL_3R_FM<0b00010, 0b011010>;
 class DIVU_ENC   : SPECIAL_3R_FM<0b00010, 0b011011>;
 class MOD_ENC    : SPECIAL_3R_FM<0b00011, 0b011010>;
@@ -115,6 +116,15 @@
 
 class AUI_DESC : AUI_DESC_BASE<"aui", GPR32Opnd>;
 
+class BITSWAP_DESC_BASE<string instr_asm, RegisterOperand GPROpnd> {
+  dag OutOperandList = (outs GPROpnd:$rd);
+  dag InOperandList = (ins GPROpnd:$rt);
+  string AsmString = !strconcat(instr_asm, "\t$rd, $rt");
+  list<dag> Pattern = [];
+}
+
+class BITSWAP_DESC : BITSWAP_DESC_BASE<"bitswap", GPR32Opnd>;
+
 class DIVMOD_DESC_BASE<string instr_asm, RegisterOperand GPROpnd> {
   dag OutOperandList = (outs GPROpnd:$rd);
   dag InOperandList = (ins GPROpnd:$rs, GPROpnd:$rt);
@@ -165,7 +175,7 @@
 def BGEZC;
 def BGTZALC;
 def BGTZC;
-def BITSWAP; // Known as BITREV in DSP ASE
+def BITSWAP : BITSWAP_ENC, BITSWAP_DESC, ISA_MIPS32R6;
 def BLEZALC;
 def BLEZC;
 def BLTC; // Also aliased to bgtc with operands swapped
Index: lib/Target/Mips/Mips64r6InstrInfo.td
===================================================================
--- lib/Target/Mips/Mips64r6InstrInfo.td
+++ lib/Target/Mips/Mips64r6InstrInfo.td
@@ -29,6 +29,7 @@
 class DAUI_ENC    : DAUI_FM;
 class DAHI_ENC    : REGIMM_FM<OPCODE5_DAHI>;
 class DATI_ENC    : REGIMM_FM<OPCODE5_DATI>;
+class DBITSWAP_ENC : SPECIAL3_2R_FM<OPCODE6_DBITSWAP>;
 class DDIV_ENC    : SPECIAL_3R_FM<0b00010, 0b011110>;
 class DDIVU_ENC   : SPECIAL_3R_FM<0b00010, 0b011111>;
 class DMOD_ENC    : SPECIAL_3R_FM<0b00011, 0b011110>;
@@ -48,6 +49,7 @@
 class DAHI_DESC    : AUI_DESC_BASE<"dahi", GPR64Opnd>;
 class DATI_DESC    : AUI_DESC_BASE<"dati", GPR64Opnd>;
 class DAUI_DESC    : AUI_DESC_BASE<"daui", GPR64Opnd>;
+class DBITSWAP_DESC : BITSWAP_DESC_BASE<"dbitswap", GPR64Opnd>;
 class DDIV_DESC    : DIVMOD_DESC_BASE<"ddiv", GPR64Opnd>;
 class DDIVU_DESC   : DIVMOD_DESC_BASE<"ddivu", GPR64Opnd>;
 class DMOD_DESC    : DIVMOD_DESC_BASE<"dmod", GPR64Opnd>;
@@ -67,7 +69,7 @@
 def DALIGN : DALIGN_ENC, DALIGN_DESC, ISA_MIPS64R6;
 def DATI : DATI_ENC, DATI_DESC, ISA_MIPS64R6;
 def DAUI : DAUI_ENC, DAUI_DESC, ISA_MIPS64R6;
-def DBITSWAP;
+def DBITSWAP : DBITSWAP_ENC, DBITSWAP_DESC, ISA_MIPS64R6;
 def DDIV : DDIV_ENC, DDIV_DESC, ISA_MIPS64R6;
 def DDIVU : DDIVU_ENC, DDIVU_DESC, ISA_MIPS64R6;
 // def DLSA; // See MSA
Index: test/MC/Mips/mips32r6/valid.s
===================================================================
--- test/MC/Mips/mips32r6/valid.s
+++ test/MC/Mips/mips32r6/valid.s
@@ -9,6 +9,7 @@
         aluipc  $3, 56           # CHECK: aluipc $3, 56       # encoding: [0xec,0x7f,0x00,0x38]
         aui     $3,$2,-23        # CHECK: aui $3, $2, -23     # encoding: [0x3c,0x62,0xff,0xe9]
         auipc   $3, -1           # CHECK: auipc $3, -1        # encoding: [0xec,0x7e,0xff,0xff]
+        bitswap $4, $2           # CHECK: bitswap $4, $2      # encoding: [0x7c,0x02,0x20,0x20]
         div     $2,$3,$4         # CHECK: div $2, $3, $4   # encoding: [0x00,0x64,0x10,0x9a]
         divu    $2,$3,$4         # CHECK: divu $2, $3, $4  # encoding: [0x00,0x64,0x10,0x9b]
         mod     $2,$3,$4         # CHECK: mod $2, $3, $4   # encoding: [0x00,0x64,0x10,0xda]
Index: test/MC/Mips/mips64r6/valid.s
===================================================================
--- test/MC/Mips/mips64r6/valid.s
+++ test/MC/Mips/mips64r6/valid.s
@@ -9,10 +9,12 @@
         aluipc  $3, 56           # CHECK: aluipc $3, 56       # encoding: [0xec,0x7f,0x00,0x38]
         aui     $3,$2,-23        # CHECK: aui $3, $2, -23     # encoding: [0x3c,0x62,0xff,0xe9]
         auipc   $3, -1           # CHECK: auipc $3, -1        # encoding: [0xec,0x7e,0xff,0xff]
+        bitswap $4, $2           # CHECK: bitswap $4, $2      # encoding: [0x7c,0x02,0x20,0x20]
         dalign  $4,$2,$3,5       # CHECK: dalign $4, $2, $3, 5 # encoding: [0x7c,0x43,0x23,0x64]
         daui    $3,$2,0x1234     # CHECK: daui $3, $2, 4660  # encoding: [0x74,0x62,0x12,0x34]
         dahi    $3,$3,0x5678     # CHECK: dahi $3, $3, 22136 # encoding: [0x04,0x66,0x56,0x78]
         dati    $3,$3,0xabcd     # CHECK: dati $3, $3, 43981 # encoding: [0x04,0x7e,0xab,0xcd]
+        dbitswap $4, $2           # CHECK: bitswap $4, $2      # encoding: [0x7c,0x02,0x20,0x24]
         div     $2,$3,$4         # CHECK: div $2, $3, $4   # encoding: [0x00,0x64,0x10,0x9a]
         divu    $2,$3,$4         # CHECK: divu $2, $3, $4  # encoding: [0x00,0x64,0x10,0x9b]
         mod     $2,$3,$4         # CHECK: mod $2, $3, $4   # encoding: [0x00,0x64,0x10,0xda]