[mips] MFC0, MTC0 changes, COP0 register class definition.

[sdardis]

Summary

Defined a new register class for coprocessor 0's registers.

The instruction definitions for DMTC0, DMFC0, MFC0 and MTC0 have been changed to reflect this.

[dsanders]

The change looks correct to me but the patch lacks appropriate test cases. Could you add them?

lib/Target/Mips/MCTargetDesc/MipsOptionRecord.cpp

82–83

Tiny nit: Could you add a small comment that the FPU is COP1? This will make the ordering of the if-statements obvious.

[sdardis]

Tests for mfc0, mtc0, and double word variants in the disassembler.
Reginfo usage test for COP0.

Is there any else required?

Thanks.

[sdardis]

Apologies, last submission had a broken test.

[dsanders]

Thanks. The tests need expanding on a bit (mostly copy/paste into each ISA's test file) and the commit message needs improving (particularly the subject line) but after that it will LGTM. I'm aware you don't have commit access yet, so could you update the revision and I'll commit from there.

To elaborate on the tests that are needed: For the disassembler, the tests you've added need to be duplicated in each ISA's test (test/MC/Disassembler/Mips/$isa/valid-$isa.txt and test/MC/Disassembler/Mips/$isa/valid-$isa-el.txt for big/little endian respectively). I believe that mfc0/mtc0 also need to be included in the tests for the 64-bit ISA's since they are still valid instructions. The tests are laid out like this to make it easy to inspect the differences between the ISA's and manually check against documentation. These files should be sorted by opcode.

For the assembler, we also need to test the encoding is correct. The existing tests for this are in test/MC/Mips/*/valid.s (one for each ISA). These files are sorted alphabetically to make it easy to verify against the documentation and inspect the ISA differences using diff. Lastly, we also need to add to test/MC/Mips/$isa1/invalid-$isa2.s which tests that $isa1 rejects things that were valid for $isa2. In this case, we just need to update the existing test/MC/Mips/*/invalid-mips64.s to check that dmfc0/dmtc0 are rejected with the correct error message. If they are rejected but with the wrong error message then there are also invalid-*-xfail.txt tests that can be used.

lib/Target/Mips/MCTargetDesc/MipsOptionRecord.cpp

84

Nit: LLVM uses '//' comments.

[sdardis]

Added tests, addressed nit.

[sdardis]

Apologies for spam attached wrong revision, this is the correct one.

[dsanders]

LGTM. I'm aware you don't have commit access yet so I'll commit this shortly.

I realize I said that disassembler tests are supposed to be sorted by opcode but it looks like they're sorted by mnemonic. You've made the correct change despite my mistake. Thanks.

[dsanders]

In the commit, I've fixed a couple issues that came up when running 'ninja check'.

• Some little endian disassembler tests failed because they had the same opcode as big endian. I've byte-swapped them.
• Two disassembler tests failed because their expectation was different for the same opcode as the other ISA's.

I also marked DMFC0 as being part of MIPS3 like the other DM[FT]C0's.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

enum RegKind {
     RegKind_MSA128 = 8,   /// MSA128[BHWD] (makes no difference which)
     RegKind_MSACtrl = 16, /// MSA control registers
     RegKind_COP2 = 32,    /// COP2
     RegKind_ACC = 64,     /// HI32DSP, LO32DSP, and ACC64DSP (depending on
                           /// context).
     RegKind_CCR = 128,    /// CCR
     RegKind_HWRegs = 256, /// HWRegs
     RegKind_COP3 = 512,   /// COP3
-
+    RegKind_COP0 = 1024,  /// COP0
     /// Potentially any (e.g. $1)
     RegKind_Numeric = RegKind_GPR | RegKind_FGR | RegKind_FCC | RegKind_MSA128 |
                       RegKind_MSACtrl | RegKind_COP2 | RegKind_ACC |
-                      RegKind_CCR | RegKind_HWRegs | RegKind_COP3
+                      RegKind_CCR | RegKind_HWRegs | RegKind_COP3 | RegKind_COP0
   };
 
 private:
   enum KindTy {
     k_Immediate,     /// An immediate (possibly involving symbol references)
     k_Memory,        /// Base + Offset Memory Address
     k_PhysRegister,  /// A physical register from the Mips namespace
     k_RegisterIndex, /// A register index in one or more RegKind.
private:
   /// Coerce the register to MSACtrl and return the real register for the
   /// current target.
   unsigned getMSACtrlReg() const {
     assert(isRegIdx() && (RegIdx.Kind & RegKind_MSACtrl) && "Invalid access!");
     unsigned ClassID = Mips::MSACtrlRegClassID;
     return RegIdx.RegInfo->getRegClass(ClassID).getRegister(RegIdx.Index);
   }
 
+  /// Coerce the register to COP0 and return the real register for the
+  /// current target.
+  unsigned getCOP0Reg() const {
+    assert(isRegIdx() && (RegIdx.Kind & RegKind_COP0) && "Invalid access!");
+    unsigned ClassID = Mips::COP0RegClassID;
+    return RegIdx.RegInfo->getRegClass(ClassID).getRegister(RegIdx.Index);
+  }
+
   /// Coerce the register to COP2 and return the real register for the
   /// current target.
   unsigned getCOP2Reg() const {
     assert(isRegIdx() && (RegIdx.Kind & RegKind_COP2) && "Invalid access!");
     unsigned ClassID = Mips::COP2RegClassID;
     return RegIdx.RegInfo->getRegClass(ClassID).getRegister(RegIdx.Index);
   }
 
void addMSA128AsmRegOperands(MCInst &Inst, unsigned N) const {
     Inst.addOperand(MCOperand::createReg(getMSA128Reg()));
   }
 
   void addMSACtrlAsmRegOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     Inst.addOperand(MCOperand::createReg(getMSACtrlReg()));
   }
 
+  void addCOP0AsmRegOperands(MCInst &Inst, unsigned N) const {
+    assert(N == 1 && "Invalid number of operands!");
+    Inst.addOperand(MCOperand::createReg(getCOP0Reg()));
+  }
+
   void addCOP2AsmRegOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     Inst.addOperand(MCOperand::createReg(getCOP2Reg()));
   }
 
   void addCOP3AsmRegOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     Inst.addOperand(MCOperand::createReg(getCOP3Reg()));
if (!(isRegIdx() && RegIdx.Kind & RegKind_FCC))
       return false;
     if (!AsmParser.hasEightFccRegisters())
       return RegIdx.Index == 0;
     return RegIdx.Index <= 7;
   }
   bool isACCAsmReg() const {
     return isRegIdx() && RegIdx.Kind & RegKind_ACC && RegIdx.Index <= 3;
   }
+  bool isCOP0AsmReg() const {
+    return isRegIdx() && RegIdx.Kind & RegKind_COP0 && RegIdx.Index <= 31;
+  }
   bool isCOP2AsmReg() const {
     return isRegIdx() && RegIdx.Kind & RegKind_COP2 && RegIdx.Index <= 31;
   }
   bool isCOP3AsmReg() const {
     return isRegIdx() && RegIdx.Kind & RegKind_COP3 && RegIdx.Index <= 31;
   }
   bool isMSA128AsmReg() const {
     return isRegIdx() && RegIdx.Kind & RegKind_MSA128 && RegIdx.Index <= 31;

lib/Target/Mips/Disassembler/MipsDisassembler.cpp

static DecodeStatus DecodeMSA128DRegisterClass(MCInst &Inst,
                                                uint64_t Address,
                                                const void *Decoder);
 
 static DecodeStatus DecodeMSACtrlRegisterClass(MCInst &Inst,
                                                unsigned RegNo,
                                                uint64_t Address,
                                                const void *Decoder);
 
+static DecodeStatus DecodeCOP0RegisterClass(MCInst &Inst,
+                                            unsigned RegNo,
+                                            uint64_t Address,
+                                            const void *Decoder);
+
 static DecodeStatus DecodeCOP2RegisterClass(MCInst &Inst,
                                             unsigned RegNo,
                                             uint64_t Address,
                                             const void *Decoder);
 
 static DecodeStatus DecodeBranchTarget(MCInst &Inst,
                                        unsigned Offset,
                                        uint64_t Address,
static DecodeStatus DecodeMSACtrlRegisterClass(MCInst &Inst,
   if (RegNo > 7)
     return MCDisassembler::Fail;
 
   unsigned Reg = getReg(Decoder, Mips::MSACtrlRegClassID, RegNo);
   Inst.addOperand(MCOperand::createReg(Reg));
   return MCDisassembler::Success;
 }
 
+static DecodeStatus DecodeCOP0RegisterClass(MCInst &Inst,
+                                            unsigned RegNo,
+                                            uint64_t Address,
+                                            const void *Decoder) {
+  if (RegNo > 31)
+    return MCDisassembler::Fail;
+
+  unsigned Reg = getReg(Decoder, Mips::COP0RegClassID, RegNo);
+  Inst.addOperand(MCOperand::createReg(Reg));
+  return MCDisassembler::Success;
+}
+
 static DecodeStatus DecodeCOP2RegisterClass(MCInst &Inst,
                                             unsigned RegNo,
                                             uint64_t Address,
                                             const void *Decoder) {
   if (RegNo > 31)
     return MCDisassembler::Fail;
 
   unsigned Reg = getReg(Decoder, Mips::COP2RegClassID, RegNo);

lib/Target/Mips/MCTargetDesc/MipsOptionRecord.cpp

for (MCSubRegIterator SubRegIt(Reg, MCRegInfo, true); SubRegIt.isValid();
     unsigned CurrentSubReg = *SubRegIt;
 
     unsigned EncVal = MCRegInfo->getEncodingValue(CurrentSubReg);
     Value |= 1 << EncVal;
 
     if (GPR32RegClass->contains(CurrentSubReg) ||
         GPR64RegClass->contains(CurrentSubReg))
       ri_gprmask |= Value;
+    else if (COP0RegClass->contains(CurrentSubReg))
+      ri_cprmask[0] |= Value;
+    /* MIPS COP1 is the FPU. */
     else if (FGR32RegClass->contains(CurrentSubReg) ||
              FGR64RegClass->contains(CurrentSubReg) ||
              AFGR64RegClass->contains(CurrentSubReg) ||
              MSA128BRegClass->contains(CurrentSubReg))
       ri_cprmask[1] |= Value;
     else if (COP2RegClass->contains(CurrentSubReg))
       ri_cprmask[2] |= Value;
     else if (COP3RegClass->contains(CurrentSubReg))
       ri_cprmask[3] |= Value;
   }
 }

lib/Target/Mips/Mips64InstrInfo.td

 def DMFC2_OCTEON : MFC2OP<"dmfc2", GPR64Opnd>, MFC2OP_FM<0x12, 1>;
 def DMTC2_OCTEON : MFC2OP<"dmtc2", GPR64Opnd>, MFC2OP_FM<0x12, 5>;
 }
 
 }
 
 /// Move between CPU and coprocessor registers
 let DecoderNamespace = "Mips64", Predicates = [HasMips64] in {
-def DMFC0 : MFC3OP<"dmfc0", GPR64Opnd>, MFC3OP_FM<0x10, 1>;
-def DMTC0 : MFC3OP<"dmtc0", GPR64Opnd>, MFC3OP_FM<0x10, 5>, ISA_MIPS3;
-def DMFC2 : MFC3OP<"dmfc2", GPR64Opnd>, MFC3OP_FM<0x12, 1>, ISA_MIPS3;
-def DMTC2 : MFC3OP<"dmtc2", GPR64Opnd>, MFC3OP_FM<0x12, 5>, ISA_MIPS3;
+def DMFC0 : MFC3OP<"dmfc0", GPR64Opnd, COP0Opnd>, MFC3OP_FM<0x10, 1>;
+def DMTC0 : MTC3OP<"dmtc0", COP0Opnd, GPR64Opnd>, MFC3OP_FM<0x10, 5>, ISA_MIPS3;
+def DMFC2 : MFC3OP<"dmfc2", GPR64Opnd, COP2Opnd>, MFC3OP_FM<0x12, 1>, ISA_MIPS3;
+def DMTC2 : MTC3OP<"dmtc2", COP2Opnd, GPR64Opnd>, MFC3OP_FM<0x12, 5>, ISA_MIPS3;
 }
 
 //===----------------------------------------------------------------------===//
 //  Arbitrary patterns that map to one or more instructions
 //===----------------------------------------------------------------------===//
 
 // extended loads
 def : MipsPat<(i64 (extloadi1  addr:$src)), (LB64 addr:$src)>;

 def : MipsInstAlias<"dsra $rd, $rt, $rs",
                     (DSRAV GPR64Opnd:$rd, GPR64Opnd:$rt, GPR32Opnd:$rs), 0>,
                     ISA_MIPS3;
 def : MipsInstAlias<"dsrl $rd, $rt, $rs",
                     (DSRLV GPR64Opnd:$rd, GPR64Opnd:$rt, GPR32Opnd:$rs), 0>,
                     ISA_MIPS3;
 
 // Two operand (implicit 0 selector) versions:
-def : MipsInstAlias<"dmfc0 $rt, $rd", (DMFC0 GPR64Opnd:$rt, GPR64Opnd:$rd, 0), 0>;
-def : MipsInstAlias<"dmtc0 $rt, $rd", (DMTC0 GPR64Opnd:$rt, GPR64Opnd:$rd, 0), 0>;
-def : MipsInstAlias<"dmfc2 $rt, $rd", (DMFC2 GPR64Opnd:$rt, GPR64Opnd:$rd, 0), 0>;
-def : MipsInstAlias<"dmtc2 $rt, $rd", (DMTC2 GPR64Opnd:$rt, GPR64Opnd:$rd, 0), 0>;
+def : MipsInstAlias<"dmfc0 $rt, $rd", (DMFC0 GPR64Opnd:$rt, COP0Opnd:$rd, 0), 0>;
+def : MipsInstAlias<"dmtc0 $rt, $rd", (DMTC0 COP0Opnd:$rd, GPR64Opnd:$rt, 0), 0>;
+def : MipsInstAlias<"dmfc2 $rt, $rd", (DMFC2 GPR64Opnd:$rt, COP2Opnd:$rd, 0), 0>;
+def : MipsInstAlias<"dmtc2 $rt, $rd", (DMTC2 COP2Opnd:$rd, GPR64Opnd:$rt, 0), 0>;
 
 let Predicates = [HasMips64, HasCnMips] in {
 def : MipsInstAlias<"synciobdma", (SYNC 0x2), 0>;
 def : MipsInstAlias<"syncs",      (SYNC 0x6), 0>;
 def : MipsInstAlias<"syncw",      (SYNC 0x4), 0>;
 def : MipsInstAlias<"syncws",     (SYNC 0x5), 0>;
 }
 
 //===----------------------------------------------------------------------===//
 // Assembler Pseudo Instructions
 //===----------------------------------------------------------------------===//
 
 class LoadImmediate64<string instr_asm, Operand Od, RegisterOperand RO> :
   MipsAsmPseudoInst<(outs RO:$rt), (ins Od:$imm64),
                      !strconcat(instr_asm, "\t$rt, $imm64")> ;
 def LoadImm64 : LoadImmediate64<"dli", imm64, GPR64Opnd>;

lib/Target/Mips/MipsInstrInfo.td

 class SCBase<string opstr, RegisterOperand RO> :
   InstSE<(outs RO:$dst), (ins RO:$rt, mem:$addr),
          !strconcat(opstr, "\t$rt, $addr"), [], NoItinerary, FrmI> {
   let DecoderMethod = "DecodeMem";
   let mayStore = 1;
   let Constraints = "$rt = $dst";
 }
 
-class MFC3OP<string asmstr, RegisterOperand RO> :
-  InstSE<(outs RO:$rt, RO:$rd, uimm16:$sel), (ins),
+class MFC3OP<string asmstr, RegisterOperand RO, RegisterOperand RD> :
+  InstSE<(outs RO:$rt), (ins RD:$rd, uimm16:$sel),
+         !strconcat(asmstr, "\t$rt, $rd, $sel"), [], NoItinerary, FrmFR>;
+
+class MTC3OP<string asmstr, RegisterOperand RO, RegisterOperand RD> :
+  InstSE<(outs RO:$rd), (ins RD:$rt, uimm16:$sel),
          !strconcat(asmstr, "\t$rt, $rd, $sel"), [], NoItinerary, FrmFR>;
 
 class TrapBase<Instruction RealInst>
   : PseudoSE<(outs), (ins), [(trap)], NoItinerary>,
     PseudoInstExpansion<(RealInst 0, 0)> {
   let isBarrier = 1;
   let isTerminator = 1;
   let isCodeGenOnly = 1;
def PseudoUDIV : MultDivPseudo<UDIV, ACC64, GPR32Opnd, MipsDivRemU, II_DIVU,
                                0, 1, 1>, ISA_MIPS1_NOT_32R6_64R6;
 
 def RDHWR : MMRel, ReadHardware<GPR32Opnd, HWRegsOpnd>, RDHWR_FM;
 
 def EXT : MMRel, ExtBase<"ext", GPR32Opnd, uimm5, MipsExt>, EXT_FM<0>;
 def INS : MMRel, InsBase<"ins", GPR32Opnd, uimm5, MipsIns>, EXT_FM<4>;
 
 /// Move Control Registers From/To CPU Registers
-def MFC0 : MFC3OP<"mfc0", GPR32Opnd>, MFC3OP_FM<0x10, 0>, ISA_MIPS32;
-def MTC0 : MFC3OP<"mtc0", GPR32Opnd>, MFC3OP_FM<0x10, 4>, ISA_MIPS32;
-def MFC2 : MFC3OP<"mfc2", GPR32Opnd>, MFC3OP_FM<0x12, 0>;
-def MTC2 : MFC3OP<"mtc2", GPR32Opnd>, MFC3OP_FM<0x12, 4>;
+def MFC0 : MFC3OP<"mfc0", GPR32Opnd, COP0Opnd>, MFC3OP_FM<0x10, 0>, ISA_MIPS32;
+def MTC0 : MTC3OP<"mtc0", COP0Opnd, GPR32Opnd>, MFC3OP_FM<0x10, 4>, ISA_MIPS32;
+def MFC2 : MFC3OP<"mfc2", GPR32Opnd, COP2Opnd>, MFC3OP_FM<0x12, 0>;
+def MTC2 : MTC3OP<"mtc2", COP2Opnd, GPR32Opnd>, MFC3OP_FM<0x12, 4>;
 
 class Barrier<string asmstr> : InstSE<(outs), (ins), asmstr, [], NoItinerary,
                                       FrmOther, asmstr>;
 def SSNOP : MMRel, Barrier<"ssnop">, BARRIER_FM<1>;
 def EHB : MMRel, Barrier<"ehb">, BARRIER_FM<3>;
 def PAUSE : MMRel, Barrier<"pause">, BARRIER_FM<5>, ISA_MIPS32R2;
 
 // JR_HB and JALR_HB are defined here using the new style naming
def : MipsInstAlias<"xor $rs, $rt, $imm",
                     (XORi GPR32Opnd:$rs, GPR32Opnd:$rt, uimm16:$imm), 0>;
 def : MipsInstAlias<"xor $rs, $imm",
                     (XORi GPR32Opnd:$rs, GPR32Opnd:$rs, uimm16:$imm), 0>;
 def : MipsInstAlias<"or $rs, $rt, $imm",
                     (ORi GPR32Opnd:$rs, GPR32Opnd:$rt, uimm16:$imm), 0>;
 def : MipsInstAlias<"or $rs, $imm",
                     (ORi GPR32Opnd:$rs, GPR32Opnd:$rs, uimm16:$imm), 0>;
 def : MipsInstAlias<"nop", (SLL ZERO, ZERO, 0), 1>;
-def : MipsInstAlias<"mfc0 $rt, $rd", (MFC0 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
-def : MipsInstAlias<"mtc0 $rt, $rd", (MTC0 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
-def : MipsInstAlias<"mfc2 $rt, $rd", (MFC2 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
-def : MipsInstAlias<"mtc2 $rt, $rd", (MTC2 GPR32Opnd:$rt, GPR32Opnd:$rd, 0), 0>;
+def : MipsInstAlias<"mfc0 $rt, $rd", (MFC0 GPR32Opnd:$rt, COP0Opnd:$rd, 0), 0>;
+def : MipsInstAlias<"mtc0 $rt, $rd", (MTC0 COP0Opnd:$rd, GPR32Opnd:$rt, 0), 0>;
+def : MipsInstAlias<"mfc2 $rt, $rd", (MFC2 GPR32Opnd:$rt, COP2Opnd:$rd, 0), 0>;
+def : MipsInstAlias<"mtc2 $rt, $rd", (MTC2 COP2Opnd:$rd, GPR32Opnd:$rt, 0), 0>;
 let AdditionalPredicates = [NotInMicroMips] in {
 def : MipsInstAlias<"b $offset", (BEQ ZERO, ZERO, brtarget:$offset), 0>;
 }
 def : MipsInstAlias<"bnez $rs,$offset",
                     (BNE GPR32Opnd:$rs, ZERO, brtarget:$offset), 0>;
 def : MipsInstAlias<"bnezl $rs,$offset",
                     (BNEL GPR32Opnd:$rs, ZERO, brtarget:$offset), 0>;
 def : MipsInstAlias<"beqz $rs,$offset",

lib/Target/Mips/MipsOptionRecord.h

MipsRegInfoRecord(MipsELFStreamer *S, MCContext &Context)
 
     const MCRegisterInfo *TRI = Context.getRegisterInfo();
     GPR32RegClass = &(TRI->getRegClass(Mips::GPR32RegClassID));
     GPR64RegClass = &(TRI->getRegClass(Mips::GPR64RegClassID));
     FGR32RegClass = &(TRI->getRegClass(Mips::FGR32RegClassID));
     FGR64RegClass = &(TRI->getRegClass(Mips::FGR64RegClassID));
     AFGR64RegClass = &(TRI->getRegClass(Mips::AFGR64RegClassID));
     MSA128BRegClass = &(TRI->getRegClass(Mips::MSA128BRegClassID));
+    COP0RegClass = &(TRI->getRegClass(Mips::COP0RegClassID));
     COP2RegClass = &(TRI->getRegClass(Mips::COP2RegClassID));
     COP3RegClass = &(TRI->getRegClass(Mips::COP3RegClassID));
   }
   ~MipsRegInfoRecord() override {}
 
   void EmitMipsOptionRecord() override;
   void SetPhysRegUsed(unsigned Reg, const MCRegisterInfo *MCRegInfo);
 
 private:
   MipsELFStreamer *Streamer;
   MCContext &Context;
   const MCRegisterClass *GPR32RegClass;
   const MCRegisterClass *GPR64RegClass;
   const MCRegisterClass *FGR32RegClass;
   const MCRegisterClass *FGR64RegClass;
   const MCRegisterClass *AFGR64RegClass;
   const MCRegisterClass *MSA128BRegClass;
+  const MCRegisterClass *COP0RegClass;
   const MCRegisterClass *COP2RegClass;
   const MCRegisterClass *COP3RegClass;
   uint32_t ri_gprmask;
   uint32_t ri_cprmask[4];
   int64_t ri_gp_value;
 };
 } // namespace llvm
 #endif

lib/Target/Mips/MipsRegisterInfo.td

let Namespace = "Mips" in {
   // FP control registers.
   foreach I = 0-31 in
   def FCR#I : MipsReg<#I, ""#I>;
 
   // FP condition code registers.
   foreach I = 0-7 in
   def FCC#I : MipsReg<#I, "fcc"#I>;
 
+  // COP0 registers.
+  foreach I = 0-31 in
+  def COP0#I : MipsReg<#I, ""#I>;
+
   // COP2 registers.
   foreach I = 0-31 in
   def COP2#I : MipsReg<#I, ""#I>;
 
   // COP3 registers.
   foreach I = 0-31 in
   def COP3#I : MipsReg<#I, ""#I>;
 

 }
 
 def ACC64DSP : RegisterClass<"Mips", [untyped], 64, (sequence "AC%u", 0, 3)> {
   let Size = 64;
 }
 
 def DSPCC : RegisterClass<"Mips", [v4i8, v2i16], 32, (add DSPCCond)>;
 
+// Coprocessor 0 registers.
+def COP0 : RegisterClass<"Mips", [i32], 32, (sequence "COP0%u", 0, 31)>,
+           Unallocatable;
+
 // Coprocessor 2 registers.
 def COP2 : RegisterClass<"Mips", [i32], 32, (sequence "COP2%u", 0, 31)>,
            Unallocatable;
 
 // Coprocessor 3 registers.
 def COP3 : RegisterClass<"Mips", [i32], 32, (sequence "COP3%u", 0, 31)>,
            Unallocatable;
 

 def CCROpnd : RegisterOperand<CCR> {
   let ParserMatchClass = CCRAsmOperand;
 }
 
 def HWRegsAsmOperand : MipsAsmRegOperand {
   let Name = "HWRegsAsmReg";
 }
 
+def COP0AsmOperand : MipsAsmRegOperand {
+  let Name = "COP0AsmReg";
+}
+
 def COP2AsmOperand : MipsAsmRegOperand {
   let Name = "COP2AsmReg";
 }
 
 def COP3AsmOperand : MipsAsmRegOperand {
   let Name = "COP3AsmReg";
 }
 

 def HI32DSPOpnd : RegisterOperand<HI32DSP> {
   let ParserMatchClass = HI32DSPAsmOperand;
 }
 
 def ACC64DSPOpnd : RegisterOperand<ACC64DSP> {
   let ParserMatchClass = ACC64DSPAsmOperand;
 }
 
+def COP0Opnd : RegisterOperand<COP0> {
+  let ParserMatchClass = COP0AsmOperand;
+}
+
 def COP2Opnd : RegisterOperand<COP2> {
   let ParserMatchClass = COP2AsmOperand;
 }
 
 def COP3Opnd : RegisterOperand<COP3> {
   let ParserMatchClass = COP3AsmOperand;
 }
 

test/MC/Disassembler/Mips/mips32.txt

 # CHECK: pref 3, 4($2)
 0xcc 0x43 0x00 0x04
 
 # CHECK: swc2  $9, 9158($7)
 0xe8 0xe9 0x23 0xc6
 
 # CHECK: lwc2  $8, 9162($6)
 0xc8 0xc8 0x23 0xca
+
+# CHECK: mfc0 $8, $16, 4
+0x40 0x08 0x80 0x04
+
+# CHECK: mtc0 $9, $15, 1
+0x40 0x89 0x78 0x01

test/MC/Disassembler/Mips/mips64.txt

 # CHECK: sdxc1 $f8, $4($25)
 0x4f 0x24 0x40 0x09
 
 # CHECK: sdc2  $9, 9158($7)
 0xf8 0xe9 0x23 0xc6
 
 # CHECK: ldc2  $3, 9162($8)
 0xd9 0x03 0x23 0xca
+
+# CHECK: dmfc0 $24, $10, 0
+0x40 0x38 0x50 0x00
+
+# CHECK: dmtc0 $4, $10, 0
+0x40 0xa4 0x50 0x00
+

test/MC/Mips/mips-cop0-reginfo.s

+# RUN: llvm-mc -arch=mips -mcpu=mips32r2 -filetype=obj %s -o - | \
+# RUN:   llvm-readobj -sections -section-data - | \
+# RUN:     FileCheck %s -check-prefix=CHECK
+  mfc0  $16, $15, 1
+  mfc0  $16, $16, 1
+
+
+# Checking for the coprocessor 0's register usage was recorded
+# and emitted.
+# CHECK:  Section {
+# CHECK:     Index: 5
+# CHECK:     Name: .reginfo (27)
+# CHECK:     Type: SHT_MIPS_REGINFO (0x70000006)
+# CHECK:     Flags [ (0x2)
+# CHECK:       SHF_ALLOC (0x2)
+# CHECK:     ]
+# CHECK:     Address: 0x0
+# CHECK:     Offset: 0x50
+# CHECK:     Size: 24
+# CHECK:     Link: 0
+# CHECK:     Info: 0
+# CHECK:     AddressAlignment: 4
+# CHECK:     EntrySize: 24
+# CHECK:     SectionData (
+# CHECK:       0000: 00010000 00018000 00000000 00000000  |................|
+# CHECK:       0010: 00000000 00000000                    |........|
+# CHECK:     )
+# CHECK:   }