Re-commit of r238201 with fix for building with shared libraries.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238739 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/AArch64/AArch64ISelDAGToDAG.cpp

@@ -156,6 +156,9 @@ public:
 
   SDNode *SelectLIBM(SDNode *N);
 
+  SDNode *SelectReadRegister(SDNode *N);
+  SDNode *SelectWriteRegister(SDNode *N);
+
 // Include the pieces autogenerated from the target description.
 #include "AArch64GenDAGISel.inc"
 
@@ -2114,6 +2117,120 @@ AArch64DAGToDAGISel::SelectCVTFixedPosOperand(SDValue N, SDValue &FixedPos,
   return true;
 }
 
+// Inspects a register string of the form o0:op1:CRn:CRm:op2 gets the fields
+// of the string and obtains the integer values from them and combines these
+// into a single value to be used in the MRS/MSR instruction.
+static int getIntOperandFromRegisterString(StringRef RegString) {
+  SmallVector<StringRef, 5> Fields;
+  RegString.split(Fields, ":");
+
+  if (Fields.size() == 1)
+    return -1;
+
+  assert(Fields.size() == 5
+            && "Invalid number of fields in read register string");
+
+  SmallVector<int, 5> Ops;
+  bool AllIntFields = true;
+
+  for (StringRef Field : Fields) {
+    unsigned IntField;
+    AllIntFields &= !Field.getAsInteger(10, IntField);
+    Ops.push_back(IntField);
+  }
+
+  assert(AllIntFields &&
+          "Unexpected non-integer value in special register string.");
+
+  // Need to combine the integer fields of the string into a single value
+  // based on the bit encoding of MRS/MSR instruction.
+  return (Ops[0] << 14) | (Ops[1] << 11) | (Ops[2] << 7) |
+         (Ops[3] << 3) | (Ops[4]);
+}
+
+// Lower the read_register intrinsic to an MRS instruction node if the special
+// register string argument is either of the form detailed in the ALCE (the
+// form described in getIntOperandsFromRegsterString) or is a named register
+// known by the MRS SysReg mapper.
+SDNode *AArch64DAGToDAGISel::SelectReadRegister(SDNode *N) {
+  const MDNodeSDNode *MD = dyn_cast<MDNodeSDNode>(N->getOperand(1));
+  const MDString *RegString = dyn_cast<MDString>(MD->getMD()->getOperand(0));
+  SDLoc DL(N);
+
+  int Reg = getIntOperandFromRegisterString(RegString->getString());
+  if (Reg != -1)
+    return CurDAG->getMachineNode(AArch64::MRS, DL, N->getSimpleValueType(0),
+                                  MVT::Other,
+                                  CurDAG->getTargetConstant(Reg, DL, MVT::i32),
+                                  N->getOperand(0));
+
+  // Use the sysreg mapper to map the remaining possible strings to the
+  // value for the register to be used for the instruction operand.
+  AArch64SysReg::MRSMapper mapper;
+  bool IsValidSpecialReg;
+  Reg = mapper.fromString(RegString->getString(),
+                          Subtarget->getFeatureBits(),
+                          IsValidSpecialReg);
+  if (IsValidSpecialReg)
+    return CurDAG->getMachineNode(AArch64::MRS, DL, N->getSimpleValueType(0),
+                                  MVT::Other,
+                                  CurDAG->getTargetConstant(Reg, DL, MVT::i32),
+                                  N->getOperand(0));
+
+  return nullptr;
+}
+
+// Lower the write_register intrinsic to an MSR instruction node if the special
+// register string argument is either of the form detailed in the ALCE (the
+// form described in getIntOperandsFromRegsterString) or is a named register
+// known by the MSR SysReg mapper.
+SDNode *AArch64DAGToDAGISel::SelectWriteRegister(SDNode *N) {
+  const MDNodeSDNode *MD = dyn_cast<MDNodeSDNode>(N->getOperand(1));
+  const MDString *RegString = dyn_cast<MDString>(MD->getMD()->getOperand(0));
+  SDLoc DL(N);
+
+  int Reg = getIntOperandFromRegisterString(RegString->getString());
+  if (Reg != -1)
+    return CurDAG->getMachineNode(AArch64::MSR, DL, MVT::Other,
+                                  CurDAG->getTargetConstant(Reg, DL, MVT::i32),
+                                  N->getOperand(2), N->getOperand(0));
+
+  // Check if the register was one of those allowed as the pstatefield value in
+  // the MSR (immediate) instruction. To accept the values allowed in the
+  // pstatefield for the MSR (immediate) instruction, we also require that an
+  // immediate value has been provided as an argument, we know that this is
+  // the case as it has been ensured by semantic checking.
+  AArch64PState::PStateMapper PMapper;
+  bool IsValidSpecialReg;
+  Reg = PMapper.fromString(RegString->getString(),
+                           Subtarget->getFeatureBits(),
+                           IsValidSpecialReg);
+  if (IsValidSpecialReg) {
+    assert (isa<ConstantSDNode>(N->getOperand(2))
+              && "Expected a constant integer expression.");
+    uint64_t Immed = cast<ConstantSDNode>(N->getOperand(2))->getZExtValue();
+    return CurDAG->getMachineNode(AArch64::MSRpstate, DL, MVT::Other,
+                                  CurDAG->getTargetConstant(Reg, DL, MVT::i32),
+                                  CurDAG->getTargetConstant(Immed, DL, MVT::i16),
+                                  N->getOperand(0));
+  }
+
+  // Use the sysreg mapper to attempt to map the remaining possible strings
+  // to the value for the register to be used for the MSR (register)
+  // instruction operand.
+  AArch64SysReg::MSRMapper Mapper;
+  Reg = Mapper.fromString(RegString->getString(),
+                          Subtarget->getFeatureBits(),
+                          IsValidSpecialReg);
+
+  if (IsValidSpecialReg)
+    return CurDAG->getMachineNode(AArch64::MSR, DL, MVT::Other,
+                                  CurDAG->getTargetConstant(Reg, DL, MVT::i32),
+                                  N->getOperand(2), N->getOperand(0));
+
+  return nullptr;
+}
+
 SDNode *AArch64DAGToDAGISel::Select(SDNode *Node) {
   // Dump information about the Node being selected
   DEBUG(errs() << "Selecting: ");
@@ -2135,6 +2252,16 @@ SDNode *AArch64DAGToDAGISel::Select(SDNode *Node) {
   default:
     break;
 
+  case ISD::READ_REGISTER:
+    if (SDNode *Res = SelectReadRegister(Node))
+      return Res;
+    break;
+
+  case ISD::WRITE_REGISTER:
+    if (SDNode *Res = SelectWriteRegister(Node))
+      return Res;
+    break;
+
   case ISD::ADD:
     if (SDNode *I = SelectMLAV64LaneV128(Node))
       return I;

lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -4065,7 +4065,8 @@ unsigned AArch64TargetLowering::getRegisterByName(const char* RegName,
                        .Default(0);
   if (Reg)
     return Reg;
-  report_fatal_error("Invalid register name global variable");
+  report_fatal_error(Twine("Invalid register name \""
+                              + StringRef(RegName)  + "\"."));
 }
 
 SDValue AArch64TargetLowering::LowerRETURNADDR(SDValue Op,

lib/Target/AArch64/LLVMBuild.txt

@@ -31,5 +31,5 @@ has_jit = 1
 type = Library
 name = AArch64CodeGen
 parent = AArch64
-required_libraries = AArch64AsmPrinter AArch64Desc AArch64Info Analysis AsmPrinter CodeGen Core MC Scalar SelectionDAG Support Target
+required_libraries = AArch64AsmPrinter AArch64Desc AArch64Info AArch64Utils Analysis AsmPrinter CodeGen Core MC Scalar SelectionDAG Support Target
 add_to_library_groups = AArch64

lib/Target/ARM/ARMISelDAGToDAG.cpp

@@ -15,6 +15,7 @@
 #include "ARMBaseInstrInfo.h"
 #include "ARMTargetMachine.h"
 #include "MCTargetDesc/ARMAddressingModes.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -251,6 +252,9 @@ private:
   // Select special operations if node forms integer ABS pattern
   SDNode *SelectABSOp(SDNode *N);
 
+  SDNode *SelectReadRegister(SDNode *N);
+  SDNode *SelectWriteRegister(SDNode *N);
+
   SDNode *SelectInlineAsm(SDNode *N);
 
   SDNode *SelectConcatVector(SDNode *N);
@@ -2457,6 +2461,18 @@ SDNode *ARMDAGToDAGISel::Select(SDNode *N) {
 
   switch (N->getOpcode()) {
   default: break;
+  case ISD::WRITE_REGISTER: {
+    SDNode *ResNode = SelectWriteRegister(N);
+    if (ResNode)
+      return ResNode;
+    break;
+  }
+  case ISD::READ_REGISTER: {
+    SDNode *ResNode = SelectReadRegister(N);
+    if (ResNode)
+      return ResNode;
+    break;
+  }
   case ISD::INLINEASM: {
     SDNode *ResNode = SelectInlineAsm(N);
     if (ResNode)
@@ -3336,6 +3352,418 @@ SDNode *ARMDAGToDAGISel::Select(SDNode *N) {
   return SelectCode(N);
 }
 
+// Inspect a register string of the form
+// cp<coprocessor>:<opc1>:c<CRn>:c<CRm>:<opc2> (32bit) or
+// cp<coprocessor>:<opc1>:c<CRm> (64bit) inspect the fields of the string
+// and obtain the integer operands from them, adding these operands to the
+// provided vector.
+static void getIntOperandsFromRegisterString(StringRef RegString,
+                                             SelectionDAG *CurDAG, SDLoc DL,
+                                             std::vector<SDValue>& Ops) {
+  SmallVector<StringRef, 5> Fields;
+  RegString.split(Fields, ":");
+
+  if (Fields.size() > 1) {
+    bool AllIntFields = true;
+
+    for (StringRef Field : Fields) {
+      // Need to trim out leading 'cp' characters and get the integer field.
+      unsigned IntField;
+      AllIntFields &= !Field.trim("CPcp").getAsInteger(10, IntField);
+      Ops.push_back(CurDAG->getTargetConstant(IntField, DL, MVT::i32));
+    }
+
+    assert(AllIntFields &&
+            "Unexpected non-integer value in special register string.");
+  }
+}
+
+// Maps a Banked Register string to its mask value. The mask value returned is
+// for use in the MRSbanked / MSRbanked instruction nodes as the Banked Register
+// mask operand, which expresses which register is to be used, e.g. r8, and in
+// which mode it is to be used, e.g. usr. Returns -1 to signify that the string
+// was invalid.
+static inline int getBankedRegisterMask(StringRef RegString) {
+  return StringSwitch<int>(RegString.lower())
+          .Case("r8_usr", 0x00)
+          .Case("r9_usr", 0x01)
+          .Case("r10_usr", 0x02)
+          .Case("r11_usr", 0x03)
+          .Case("r12_usr", 0x04)
+          .Case("sp_usr", 0x05)
+          .Case("lr_usr", 0x06)
+          .Case("r8_fiq", 0x08)
+          .Case("r9_fiq", 0x09)
+          .Case("r10_fiq", 0x0a)
+          .Case("r11_fiq", 0x0b)
+          .Case("r12_fiq", 0x0c)
+          .Case("sp_fiq", 0x0d)
+          .Case("lr_fiq", 0x0e)
+          .Case("lr_irq", 0x10)
+          .Case("sp_irq", 0x11)
+          .Case("lr_svc", 0x12)
+          .Case("sp_svc", 0x13)
+          .Case("lr_abt", 0x14)
+          .Case("sp_abt", 0x15)
+          .Case("lr_und", 0x16)
+          .Case("sp_und", 0x17)
+          .Case("lr_mon", 0x1c)
+          .Case("sp_mon", 0x1d)
+          .Case("elr_hyp", 0x1e)
+          .Case("sp_hyp", 0x1f)
+          .Case("spsr_fiq", 0x2e)
+          .Case("spsr_irq", 0x30)
+          .Case("spsr_svc", 0x32)
+          .Case("spsr_abt", 0x34)
+          .Case("spsr_und", 0x36)
+          .Case("spsr_mon", 0x3c)
+          .Case("spsr_hyp", 0x3e)
+          .Default(-1);
+}
+
+// Maps a MClass special register string to its value for use in the
+// t2MRS_M / t2MSR_M instruction nodes as the SYSm value operand.
+// Returns -1 to signify that the string was invalid.
+static inline int getMClassRegisterSYSmValueMask(StringRef RegString) {
+  return StringSwitch<int>(RegString.lower())
+          .Case("apsr", 0x0)
+          .Case("iapsr", 0x1)
+          .Case("eapsr", 0x2)
+          .Case("xpsr", 0x3)
+          .Case("ipsr", 0x5)
+          .Case("epsr", 0x6)
+          .Case("iepsr", 0x7)
+          .Case("msp", 0x8)
+          .Case("psp", 0x9)
+          .Case("primask", 0x10)
+          .Case("basepri", 0x11)
+          .Case("basepri_max", 0x12)
+          .Case("faultmask", 0x13)
+          .Case("control", 0x14)
+          .Default(-1);
+}
+
+// The flags here are common to those allowed for apsr in the A class cores and
+// those allowed for the special registers in the M class cores. Returns a
+// value representing which flags were present, -1 if invalid.
+static inline int getMClassFlagsMask(StringRef Flags) {
+  if (Flags.empty())
+    return 0x3;
+
+  return StringSwitch<int>(Flags)
+          .Case("g", 0x1)
+          .Case("nzcvq", 0x2)
+          .Case("nzcvqg", 0x3)
+          .Default(-1);
+}
+
+static int getMClassRegisterMask(StringRef Reg, StringRef Flags, bool IsRead,
+                                 const ARMSubtarget *Subtarget) {
+  // Ensure that the register (without flags) was a valid M Class special
+  // register.
+  int SYSmvalue = getMClassRegisterSYSmValueMask(Reg);
+  if (SYSmvalue == -1)
+    return -1;
+
+  // basepri, basepri_max and faultmask are only valid for V7m.
+  if (!Subtarget->hasV7Ops() && SYSmvalue >= 0x11 && SYSmvalue <= 0x13)
+    return -1;
+
+  // If it was a read then we won't be expecting flags and so at this point
+  // we can return the mask.
+  if (IsRead) {
+    assert (Flags.empty() && "Unexpected flags for reading M class register.");
+    return SYSmvalue;
+  }
+
+  // We know we are now handling a write so need to get the mask for the flags.
+  int Mask = getMClassFlagsMask(Flags);
+
+  // Only apsr, iapsr, eapsr, xpsr can have flags. The other register values
+  // shouldn't have flags present.
+  if ((SYSmvalue < 0x4 && Mask == -1) || (SYSmvalue > 0x4 && !Flags.empty()))
+    return -1;
+
+  // The _g and _nzcvqg versions are only valid if the DSP extension is
+  // available.
+  if (!Subtarget->hasThumb2DSP() && (Mask & 0x2))
+    return -1;
+
+  // The register was valid so need to put the mask in the correct place
+  // (the flags need to be in bits 11-10) and combine with the SYSmvalue to
+  // construct the operand for the instruction node.
+  if (SYSmvalue < 0x4)
+    return SYSmvalue | Mask << 10;
+
+  return SYSmvalue;
+}
+
+static int getARClassRegisterMask(StringRef Reg, StringRef Flags) {
+  // The mask operand contains the special register (R Bit) in bit 4, whether
+  // the register is spsr (R bit is 1) or one of cpsr/apsr (R bit is 0), and
+  // bits 3-0 contains the fields to be accessed in the special register, set by
+  // the flags provided with the register.
+  int Mask = 0;
+  if (Reg == "apsr") {
+    // The flags permitted for apsr are the same flags that are allowed in
+    // M class registers. We get the flag value and then shift the flags into
+    // the correct place to combine with the mask.
+    Mask = getMClassFlagsMask(Flags);
+    if (Mask == -1)
+      return -1;
+    return Mask << 2;
+  }
+
+  if (Reg != "cpsr" && Reg != "spsr") {
+    return -1;
+  }
+
+  // This is the same as if the flags were "fc"
+  if (Flags.empty() || Flags == "all")
+    return Mask | 0x9;
+
+  // Inspect the supplied flags string and set the bits in the mask for
+  // the relevant and valid flags allowed for cpsr and spsr.
+  for (char Flag : Flags) {
+    int FlagVal;
+    switch (Flag) {
+      case 'c':
+        FlagVal = 0x1;
+        break;
+      case 'x':
+        FlagVal = 0x2;
+        break;
+      case 's':
+        FlagVal = 0x4;
+        break;
+      case 'f':
+        FlagVal = 0x8;
+        break;
+      default:
+        FlagVal = 0;
+    }
+
+    // This avoids allowing strings where the same flag bit appears twice.
+    if (!FlagVal || (Mask & FlagVal))
+      return -1;
+    Mask |= FlagVal;
+  }
+
+  // If the register is spsr then we need to set the R bit.
+  if (Reg == "spsr")
+    Mask |= 0x10;
+
+  return Mask;
+}
+
+// Lower the read_register intrinsic to ARM specific DAG nodes
+// using the supplied metadata string to select the instruction node to use
+// and the registers/masks to construct as operands for the node.
+SDNode *ARMDAGToDAGISel::SelectReadRegister(SDNode *N){
+  const MDNodeSDNode *MD = dyn_cast<MDNodeSDNode>(N->getOperand(1));
+  const MDString *RegString = dyn_cast<MDString>(MD->getMD()->getOperand(0));
+  bool IsThumb2 = Subtarget->isThumb2();
+  SDLoc DL(N);
+
+  std::vector<SDValue> Ops;
+  getIntOperandsFromRegisterString(RegString->getString(), CurDAG, DL, Ops);
+
+  if (!Ops.empty()) {
+    // If the special register string was constructed of fields (as defined
+    // in the ACLE) then need to lower to MRC node (32 bit) or
+    // MRRC node(64 bit), we can make the distinction based on the number of
+    // operands we have.
+    unsigned Opcode;
+    SmallVector<EVT, 3> ResTypes;
+    if (Ops.size() == 5){
+      Opcode = IsThumb2 ? ARM::t2MRC : ARM::MRC;
+      ResTypes.append({ MVT::i32, MVT::Other });
+    } else {
+      assert(Ops.size() == 3 &&
+              "Invalid number of fields in special register string.");
+      Opcode = IsThumb2 ? ARM::t2MRRC : ARM::MRRC;
+      ResTypes.append({ MVT::i32, MVT::i32, MVT::Other });
+    }
+
+    Ops.push_back(getAL(CurDAG, DL));
+    Ops.push_back(CurDAG->getRegister(0, MVT::i32));
+    Ops.push_back(N->getOperand(0));
+    return CurDAG->getMachineNode(Opcode, DL, ResTypes, Ops);
+  }
+
+  std::string SpecialReg = RegString->getString().lower();
+
+  int BankedReg = getBankedRegisterMask(SpecialReg);
+  if (BankedReg != -1) {
+    Ops = { CurDAG->getTargetConstant(BankedReg, DL, MVT::i32),
+            getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+            N->getOperand(0) };
+    return CurDAG->getMachineNode(IsThumb2 ? ARM::t2MRSbanked : ARM::MRSbanked,
+                                  DL, MVT::i32, MVT::Other, Ops);
+  }
+
+  // The VFP registers are read by creating SelectionDAG nodes with opcodes
+  // corresponding to the register that is being read from. So we switch on the
+  // string to find which opcode we need to use.
+  unsigned Opcode = StringSwitch<unsigned>(SpecialReg)
+                    .Case("fpscr", ARM::VMRS)
+                    .Case("fpexc", ARM::VMRS_FPEXC)
+                    .Case("fpsid", ARM::VMRS_FPSID)
+                    .Case("mvfr0", ARM::VMRS_MVFR0)
+                    .Case("mvfr1", ARM::VMRS_MVFR1)
+                    .Case("mvfr2", ARM::VMRS_MVFR2)
+                    .Case("fpinst", ARM::VMRS_FPINST)
+                    .Case("fpinst2", ARM::VMRS_FPINST2)
+                    .Default(0);
+
+  // If an opcode was found then we can lower the read to a VFP instruction.
+  if (Opcode) {
+    if (!Subtarget->hasVFP2())
+      return nullptr;
+    if (Opcode == ARM::VMRS_MVFR2 && !Subtarget->hasFPARMv8())
+      return nullptr;
+
+    Ops = { getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+            N->getOperand(0) };
+    return CurDAG->getMachineNode(Opcode, DL, MVT::i32, MVT::Other, Ops);
+  }
+
+  // If the target is M Class then need to validate that the register string
+  // is an acceptable value, so check that a mask can be constructed from the
+  // string.
+  if (Subtarget->isMClass()) {
+    int SYSmValue = getMClassRegisterMask(SpecialReg, "", true, Subtarget);
+    if (SYSmValue == -1)
+      return nullptr;
+
+    SDValue Ops[] = { CurDAG->getTargetConstant(SYSmValue, DL, MVT::i32),
+                      getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+                      N->getOperand(0) };
+    return CurDAG->getMachineNode(ARM::t2MRS_M, DL, MVT::i32, MVT::Other, Ops);
+  }
+
+  // Here we know the target is not M Class so we need to check if it is one
+  // of the remaining possible values which are apsr, cpsr or spsr.
+  if (SpecialReg == "apsr" || SpecialReg == "cpsr") {
+    Ops = { getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+            N->getOperand(0) };
+    return CurDAG->getMachineNode(IsThumb2 ? ARM::t2MRS_AR : ARM::MRS, DL,
+                                  MVT::i32, MVT::Other, Ops);
+  }
+
+  if (SpecialReg == "spsr") {
+    Ops = { getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+            N->getOperand(0) };
+    return CurDAG->getMachineNode(IsThumb2 ? ARM::t2MRSsys_AR : ARM::MRSsys,
+                                  DL, MVT::i32, MVT::Other, Ops);
+  }
+
+  return nullptr;
+}
+
+// Lower the write_register intrinsic to ARM specific DAG nodes
+// using the supplied metadata string to select the instruction node to use
+// and the registers/masks to use in the nodes
+SDNode *ARMDAGToDAGISel::SelectWriteRegister(SDNode *N){
+  const MDNodeSDNode *MD = dyn_cast<MDNodeSDNode>(N->getOperand(1));
+  const MDString *RegString = dyn_cast<MDString>(MD->getMD()->getOperand(0));
+  bool IsThumb2 = Subtarget->isThumb2();
+  SDLoc DL(N);
+
+  std::vector<SDValue> Ops;
+  getIntOperandsFromRegisterString(RegString->getString(), CurDAG, DL, Ops);
+
+  if (!Ops.empty()) {
+    // If the special register string was constructed of fields (as defined
+    // in the ACLE) then need to lower to MCR node (32 bit) or
+    // MCRR node(64 bit), we can make the distinction based on the number of
+    // operands we have.
+    unsigned Opcode;
+    if (Ops.size() == 5) {
+      Opcode = IsThumb2 ? ARM::t2MCR : ARM::MCR;
+      Ops.insert(Ops.begin()+2, N->getOperand(2));
+    } else {
+      assert(Ops.size() == 3 &&
+              "Invalid number of fields in special register string.");
+      Opcode = IsThumb2 ? ARM::t2MCRR : ARM::MCRR;
+      SDValue WriteValue[] = { N->getOperand(2), N->getOperand(3) };
+      Ops.insert(Ops.begin()+2, WriteValue, WriteValue+2);
+    }
+
+    Ops.push_back(getAL(CurDAG, DL));
+    Ops.push_back(CurDAG->getRegister(0, MVT::i32));
+    Ops.push_back(N->getOperand(0));
+
+    return CurDAG->getMachineNode(Opcode, DL, MVT::Other, Ops);
+  }
+
+  std::string SpecialReg = RegString->getString().lower();
+  int BankedReg = getBankedRegisterMask(SpecialReg);
+  if (BankedReg != -1) {
+    Ops = { CurDAG->getTargetConstant(BankedReg, DL, MVT::i32), N->getOperand(2),
+            getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+            N->getOperand(0) };
+    return CurDAG->getMachineNode(IsThumb2 ? ARM::t2MSRbanked : ARM::MSRbanked,
+                                  DL, MVT::Other, Ops);
+  }
+
+  // The VFP registers are written to by creating SelectionDAG nodes with
+  // opcodes corresponding to the register that is being written. So we switch
+  // on the string to find which opcode we need to use.
+  unsigned Opcode = StringSwitch<unsigned>(SpecialReg)
+                    .Case("fpscr", ARM::VMSR)
+                    .Case("fpexc", ARM::VMSR_FPEXC)
+                    .Case("fpsid", ARM::VMSR_FPSID)
+                    .Case("fpinst", ARM::VMSR_FPINST)
+                    .Case("fpinst2", ARM::VMSR_FPINST2)
+                    .Default(0);
+
+  if (Opcode) {
+    if (!Subtarget->hasVFP2())
+      return nullptr;
+    Ops = { N->getOperand(2), getAL(CurDAG, DL),
+            CurDAG->getRegister(0, MVT::i32), N->getOperand(0) };
+    return CurDAG->getMachineNode(Opcode, DL, MVT::Other, Ops);
+  }
+
+  SmallVector<StringRef, 5> Fields;
+  StringRef(SpecialReg).split(Fields, "_", 1, false);
+  std::string Reg = Fields[0].str();
+  StringRef Flags = Fields.size() == 2 ? Fields[1] : "";
+
+  // If the target was M Class then need to validate the special register value
+  // and retrieve the mask for use in the instruction node.
+  if (Subtarget->isMClass()) {
+    // basepri_max gets split so need to correct Reg and Flags.
+    if (SpecialReg == "basepri_max") {
+      Reg = SpecialReg;
+      Flags = "";
+    }
+    int SYSmValue = getMClassRegisterMask(Reg, Flags, false, Subtarget);
+    if (SYSmValue == -1)
+      return nullptr;
+
+    SDValue Ops[] = { CurDAG->getTargetConstant(SYSmValue, DL, MVT::i32),
+                      N->getOperand(2), getAL(CurDAG, DL),
+                      CurDAG->getRegister(0, MVT::i32), N->getOperand(0) };
+    return CurDAG->getMachineNode(ARM::t2MSR_M, DL, MVT::Other, Ops);
+  }
+
+  // We then check to see if a valid mask can be constructed for one of the
+  // register string values permitted for the A and R class cores. These values
+  // are apsr, spsr and cpsr; these are also valid on older cores.
+  int Mask = getARClassRegisterMask(Reg, Flags);
+  if (Mask != -1) {
+    Ops = { CurDAG->getTargetConstant(Mask, DL, MVT::i32), N->getOperand(2),
+            getAL(CurDAG, DL), CurDAG->getRegister(0, MVT::i32),
+            N->getOperand(0) };
+    return CurDAG->getMachineNode(IsThumb2 ? ARM::t2MSR_AR : ARM::MSR,
+                                  DL, MVT::Other, Ops);
+  }
+
+  return nullptr;
+}
+
 SDNode *ARMDAGToDAGISel::SelectInlineAsm(SDNode *N){
   std::vector<SDValue> AsmNodeOperands;
   unsigned Flag, Kind;

lib/Target/ARM/ARMISelLowering.cpp

@@ -426,6 +426,9 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::ConstantFP, MVT::f32, Custom);
   setOperationAction(ISD::ConstantFP, MVT::f64, Custom);
 
+  setOperationAction(ISD::READ_REGISTER, MVT::i64, Custom);
+  setOperationAction(ISD::WRITE_REGISTER, MVT::i64, Custom);
+
   if (Subtarget->hasNEON()) {
     addDRTypeForNEON(MVT::v2f32);
     addDRTypeForNEON(MVT::v8i8);
@@ -2379,6 +2382,24 @@ bool ARMTargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
   return !Subtarget->isThumb1Only();
 }
 
+// Trying to write a 64 bit value so need to split into two 32 bit values first,
+// and pass the lower and high parts through.
+static SDValue LowerWRITE_REGISTER(SDValue Op, SelectionDAG &DAG) {
+  SDLoc DL(Op);
+  SDValue WriteValue = Op->getOperand(2);
+
+  // This function is only supposed to be called for i64 type argument.
+  assert(WriteValue.getValueType() == MVT::i64
+          && "LowerWRITE_REGISTER called for non-i64 type argument.");
+
+  SDValue Lo = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i32, WriteValue,
+                           DAG.getConstant(0, DL, MVT::i32));
+  SDValue Hi = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i32, WriteValue,
+                           DAG.getConstant(1, DL, MVT::i32));
+  SDValue Ops[] = { Op->getOperand(0), Op->getOperand(1), Lo, Hi };
+  return DAG.getNode(ISD::WRITE_REGISTER, DL, MVT::Other, Ops);
+}
+
 // ConstantPool, JumpTable, GlobalAddress, and ExternalSymbol are lowered as
 // their target counterpart wrapped in the ARMISD::Wrapper node. Suppose N is
 // one of the above mentioned nodes. It has to be wrapped because otherwise
@@ -4086,7 +4107,28 @@ unsigned ARMTargetLowering::getRegisterByName(const char* RegName,
                        .Default(0);
   if (Reg)
     return Reg;
-  report_fatal_error("Invalid register name global variable");
+  report_fatal_error(Twine("Invalid register name \""
+                              + StringRef(RegName)  + "\"."));
+}
+
+// Result is 64 bit value so split into two 32 bit values and return as a
+// pair of values.
+static void ExpandREAD_REGISTER(SDNode *N, SmallVectorImpl<SDValue> &Results,
+                                SelectionDAG &DAG) {
+  SDLoc DL(N);
+
+  // This function is only supposed to be called for i64 type destination.
+  assert(N->getValueType(0) == MVT::i64
+          && "ExpandREAD_REGISTER called for non-i64 type result.");
+
+  SDValue Read = DAG.getNode(ISD::READ_REGISTER, DL,
+                             DAG.getVTList(MVT::i32, MVT::i32, MVT::Other),
+                             N->getOperand(0),
+                             N->getOperand(1));
+
+  Results.push_back(DAG.getNode(ISD::BUILD_PAIR, DL, MVT::i64, Read.getValue(0),
+                    Read.getValue(1)));
+  Results.push_back(Read.getOperand(0));
 }
 
 /// ExpandBITCAST - If the target supports VFP, this function is called to
@@ -6356,6 +6398,7 @@ static void ReplaceREADCYCLECOUNTER(SDNode *N,
 SDValue ARMTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
   default: llvm_unreachable("Don't know how to custom lower this!");
+  case ISD::WRITE_REGISTER: return LowerWRITE_REGISTER(Op, DAG);
   case ISD::ConstantPool:  return LowerConstantPool(Op, DAG);
   case ISD::BlockAddress:  return LowerBlockAddress(Op, DAG);
   case ISD::GlobalAddress:
@@ -6440,6 +6483,9 @@ void ARMTargetLowering::ReplaceNodeResults(SDNode *N,
   switch (N->getOpcode()) {
   default:
     llvm_unreachable("Don't know how to custom expand this!");
+  case ISD::READ_REGISTER:
+    ExpandREAD_REGISTER(N, Results, DAG);
+    break;
   case ISD::BITCAST:
     Res = ExpandBITCAST(N, DAG);
     break;

lib/Target/ARM/ARMInstrInfo.td

@@ -5080,10 +5080,11 @@ def : ARMV5TPat<(int_arm_mrc2 imm:$cop, imm:$opc1, imm:$CRn,
                               imm:$CRm, imm:$opc2),
                 (MRC2 imm:$cop, imm:$opc1, imm:$CRn, imm:$CRm, imm:$opc2)>;
 
-class MovRRCopro<string opc, bit direction, list<dag> pattern = []>
+class MovRRCopro<string opc, bit direction, dag oops, dag iops, list<dag>
-  : ABI<0b1100, (outs), (ins p_imm:$cop, imm0_15:$opc1,
+                 pattern = []>
-        GPRnopc:$Rt, GPRnopc:$Rt2, c_imm:$CRm),
+  : ABI<0b1100, oops, iops, NoItinerary, opc, "\t$cop, $opc1, $Rt, $Rt2, $CRm",
-        NoItinerary, opc, "\t$cop, $opc1, $Rt, $Rt2, $CRm", pattern> {
+        pattern> {
+
   let Inst{23-21} = 0b010;
   let Inst{20} = direction;
 
@@ -5101,9 +5102,13 @@ class MovRRCopro<string opc, bit direction, list<dag> pattern = []>
 }
 
 def MCRR : MovRRCopro<"mcrr", 0 /* from ARM core register to coprocessor */,
+                      (outs), (ins p_imm:$cop, imm0_15:$opc1, GPRnopc:$Rt,
+                      GPRnopc:$Rt2, c_imm:$CRm),
                       [(int_arm_mcrr imm:$cop, imm:$opc1, GPRnopc:$Rt,
                                      GPRnopc:$Rt2, imm:$CRm)]>;
-def MRRC : MovRRCopro<"mrrc", 1 /* from coprocessor to ARM core register */>;
+def MRRC : MovRRCopro<"mrrc", 1 /* from coprocessor to ARM core register */,
+                      (outs GPRnopc:$Rt, GPRnopc:$Rt2),
+                      (ins p_imm:$cop, imm0_15:$opc1, c_imm:$CRm), []>;
 
 class MovRRCopro2<string opc, bit direction, list<dag> pattern = []>
   : ABXI<0b1100, (outs), (ins p_imm:$cop, imm0_15:$opc1,

lib/Target/ARM/ARMInstrThumb2.td

@@ -4141,11 +4141,9 @@ class t2MovRCopro<bits<4> Op, string opc, bit direction, dag oops, dag iops,
   let Inst{19-16} = CRn;
 }
 
-class t2MovRRCopro<bits<4> Op, string opc, bit direction,
+class t2MovRRCopro<bits<4> Op, string opc, bit direction, dag oops, dag iops,
                    list<dag> pattern = []>
-  : T2Cop<Op, (outs),
+  : T2Cop<Op, oops, iops, opc, "\t$cop, $opc1, $Rt, $Rt2, $CRm", pattern> {
-          (ins p_imm:$cop, imm0_15:$opc1, GPR:$Rt, GPR:$Rt2, c_imm:$CRm),
-          opc, "\t$cop, $opc1, $Rt, $Rt2, $CRm", pattern> {
   let Inst{27-24} = 0b1100;
   let Inst{23-21} = 0b010;
   let Inst{20} = direction;
@@ -4210,19 +4208,25 @@ def : T2v6Pat<(int_arm_mrc2 imm:$cop, imm:$opc1, imm:$CRn, imm:$CRm, imm:$opc2),
 
 
 /* from ARM core register to coprocessor */
-def t2MCRR : t2MovRRCopro<0b1110, "mcrr", 0,
+def t2MCRR : t2MovRRCopro<0b1110, "mcrr", 0, (outs),
+                         (ins p_imm:$cop, imm0_15:$opc1, GPR:$Rt, GPR:$Rt2,
+                         c_imm:$CRm),
                         [(int_arm_mcrr imm:$cop, imm:$opc1, GPR:$Rt, GPR:$Rt2,
                                        imm:$CRm)]>;
-def t2MCRR2 : t2MovRRCopro<0b1111, "mcrr2", 0,
+def t2MCRR2 : t2MovRRCopro<0b1111, "mcrr2", 0, (outs),
-                           [(int_arm_mcrr2 imm:$cop, imm:$opc1, GPR:$Rt,
+                          (ins p_imm:$cop, imm0_15:$opc1, GPR:$Rt, GPR:$Rt2,
-                                           GPR:$Rt2, imm:$CRm)]> {
+                           c_imm:$CRm),
+                          [(int_arm_mcrr2 imm:$cop, imm:$opc1, GPR:$Rt,
+                                          GPR:$Rt2, imm:$CRm)]> {
   let Predicates = [IsThumb2, PreV8];
 }
 
 /* from coprocessor to ARM core register */
-def t2MRRC : t2MovRRCopro<0b1110, "mrrc", 1>;
+def t2MRRC : t2MovRRCopro<0b1110, "mrrc", 1, (outs GPR:$Rt, GPR:$Rt2),
+                          (ins p_imm:$cop, imm0_15:$opc1, c_imm:$CRm)>;
 
-def t2MRRC2 : t2MovRRCopro<0b1111, "mrrc2", 1> {
+def t2MRRC2 : t2MovRRCopro<0b1111, "mrrc2", 1, (outs GPR:$Rt, GPR:$Rt2),
+                           (ins p_imm:$cop, imm0_15:$opc1, c_imm:$CRm)> {
   let Predicates = [IsThumb2, PreV8];
 }
 

test/CodeGen/AArch64/arm64-named-reg-alloc.ll

@@ -4,7 +4,7 @@
 define i32 @get_stack() nounwind {
 entry:
 ; FIXME: Include an allocatable-specific error message
-; CHECK: Invalid register name global variable
+; CHECK: Invalid register name "x5".
 	%sp = call i32 @llvm.read_register.i32(metadata !0)
   ret i32 %sp
 }

test/CodeGen/AArch64/arm64-named-reg-notareg.ll

@@ -3,7 +3,7 @@
 
 define i32 @get_stack() nounwind {
 entry:
-; CHECK: Invalid register name global variable
+; CHECK: Invalid register name "notareg".
 	%sp = call i32 @llvm.read_register.i32(metadata !0)
   ret i32 %sp
 }

test/CodeGen/AArch64/special-reg.ll

@@ -0,0 +1,48 @@
+; RUN: llc < %s -mtriple=aarch64-none-eabi -mcpu=cortex-a57 2>&1 | FileCheck %s
+
+define i64 @read_encoded_register() nounwind {
+entry:
+; CHECK-LABEL: read_encoded_register:
+; CHECK: mrs x0, S1_2_C3_C4_5
+  %reg = call i64 @llvm.read_register.i64(metadata !0)
+  ret i64 %reg
+}
+
+define i64 @read_daif() nounwind {
+entry:
+; CHECK-LABEL: read_daif:
+; CHECK: mrs x0, DAIF
+  %reg = call i64 @llvm.read_register.i64(metadata !1)
+  ret i64 %reg
+}
+
+define void @write_encoded_register(i64 %x) nounwind {
+entry:
+; CHECK-LABEL: write_encoded_register:
+; CHECK: msr S1_2_C3_C4_5, x0
+  call void @llvm.write_register.i64(metadata !0, i64 %x)
+  ret void
+}
+
+define void @write_daif(i64 %x) nounwind {
+entry:
+; CHECK-LABEL: write_daif:
+; CHECK: msr DAIF, x0
+  call void @llvm.write_register.i64(metadata !1, i64 %x)
+  ret void
+}
+
+define void @write_daifset() nounwind {
+entry:
+; CHECK-LABEL: write_daifset:
+; CHECK: msr DAIFSET, #2
+  call void @llvm.write_register.i64(metadata !2, i64 2)
+  ret void
+}
+
+declare i64 @llvm.read_register.i64(metadata) nounwind
+declare void @llvm.write_register.i64(metadata, i64) nounwind
+
+!0 = !{!"1:2:3:4:5"}
+!1 = !{!"daif"}
+!2 = !{!"daifset"}

test/CodeGen/AArch64/special-reg.s.s

@@ -0,0 +1,3 @@
+	.section	__TEXT,__text,regular,pure_instructions
+
+.subsections_via_symbols

test/CodeGen/ARM/named-reg-alloc.ll

@@ -4,7 +4,7 @@
 define i32 @get_stack() nounwind {
 entry:
 ; FIXME: Include an allocatable-specific error message
-; CHECK: Invalid register name global variable
+; CHECK: Invalid register name "r5".
 	%sp = call i32 @llvm.read_register.i32(metadata !0)
   ret i32 %sp
 }

test/CodeGen/ARM/named-reg-notareg.ll

@@ -3,7 +3,7 @@
 
 define i32 @get_stack() nounwind {
 entry:
-; CHECK: Invalid register name global variable
+; CHECK: Invalid register name "notareg".
 	%sp = call i32 @llvm.read_register.i32(metadata !0)
   ret i32 %sp
 }

test/CodeGen/ARM/special-reg-acore.ll

@@ -0,0 +1,78 @@
+; RUN: llc < %s -mtriple=arm-none-eabi -mcpu=cortex-a8 2>&1 | FileCheck %s --check-prefix=ACORE
+; RUN: not llc < %s -mtriple=thumb-none-eabi -mcpu=cortex-m4 2>&1 | FileCheck %s --check-prefix=MCORE
+
+; MCORE: LLVM ERROR: Invalid register name "cpsr".
+
+define i32 @read_cpsr() nounwind {
+  ; ACORE-LABEL: read_cpsr:
+  ; ACORE: mrs r0, apsr
+  %reg = call i32 @llvm.read_register.i32(metadata !1)
+  ret i32 %reg
+}
+
+define i32 @read_aclass_registers() nounwind {
+entry:
+  ; ACORE-LABEL: read_aclass_registers:
+  ; ACORE: mrs r0, apsr
+  ; ACORE: mrs r1, spsr
+
+  %0 = call i32 @llvm.read_register.i32(metadata !0)
+  %1 = call i32 @llvm.read_register.i32(metadata !1)
+  %add1 = add i32 %1, %0
+  %2 = call i32 @llvm.read_register.i32(metadata !2)
+  %add2 = add i32 %add1, %2
+  ret i32 %add2
+}
+
+define void @write_aclass_registers(i32 %x) nounwind {
+entry:
+  ; ACORE-LABEL: write_aclass_registers:
+  ; ACORE:   msr APSR_nzcvq, r0
+  ; ACORE:   msr APSR_g, r0
+  ; ACORE:   msr APSR_nzcvqg, r0
+  ; ACORE:   msr CPSR_c, r0
+  ; ACORE:   msr CPSR_x, r0
+  ; ACORE:   msr APSR_g, r0
+  ; ACORE:   msr APSR_nzcvq, r0
+  ; ACORE:   msr CPSR_fsxc, r0
+  ; ACORE:   msr SPSR_c, r0
+  ; ACORE:   msr SPSR_x, r0
+  ; ACORE:   msr SPSR_s, r0
+  ; ACORE:   msr SPSR_f, r0
+  ; ACORE:   msr SPSR_fsxc, r0
+
+  call void @llvm.write_register.i32(metadata !3, i32 %x)
+  call void @llvm.write_register.i32(metadata !4, i32 %x)
+  call void @llvm.write_register.i32(metadata !5, i32 %x)
+  call void @llvm.write_register.i32(metadata !6, i32 %x)
+  call void @llvm.write_register.i32(metadata !7, i32 %x)
+  call void @llvm.write_register.i32(metadata !8, i32 %x)
+  call void @llvm.write_register.i32(metadata !9, i32 %x)
+  call void @llvm.write_register.i32(metadata !10, i32 %x)
+  call void @llvm.write_register.i32(metadata !11, i32 %x)
+  call void @llvm.write_register.i32(metadata !12, i32 %x)
+  call void @llvm.write_register.i32(metadata !13, i32 %x)
+  call void @llvm.write_register.i32(metadata !14, i32 %x)
+  call void @llvm.write_register.i32(metadata !15, i32 %x)
+  ret void
+}
+
+declare i32 @llvm.read_register.i32(metadata) nounwind
+declare void @llvm.write_register.i32(metadata, i32) nounwind
+
+!0 = !{!"apsr"}
+!1 = !{!"cpsr"}
+!2 = !{!"spsr"}
+!3 = !{!"apsr_nzcvq"}
+!4 = !{!"apsr_g"}
+!5 = !{!"apsr_nzcvqg"}
+!6 = !{!"cpsr_c"}
+!7 = !{!"cpsr_x"}
+!8 = !{!"cpsr_s"}
+!9 = !{!"cpsr_f"}
+!10 = !{!"cpsr_cxsf"}
+!11 = !{!"spsr_c"}
+!12 = !{!"spsr_x"}
+!13 = !{!"spsr_s"}
+!14 = !{!"spsr_f"}
+!15 = !{!"spsr_cxsf"}

test/CodeGen/ARM/special-reg-mcore.ll

@@ -0,0 +1,143 @@
+; RUN: llc < %s -mtriple=thumb-none-eabi -mcpu=cortex-m4 2>&1 | FileCheck %s --check-prefix=MCORE
+; RUN: not llc < %s -mtriple=thumb-none-eabi -mcpu=cortex-m3 2>&1 | FileCheck %s --check-prefix=M3CORE
+; RUN: not llc < %s -mtriple=arm-none-eabi -mcpu=cortex-a8 2>&1 | FileCheck %s --check-prefix=ACORE
+
+; ACORE: LLVM ERROR: Invalid register name "control".
+; M3CORE: LLVM ERROR: Invalid register name "control".
+
+define i32 @read_mclass_registers() nounwind {
+entry:
+  ; MCORE-LABEL: read_mclass_registers:
+  ; MCORE:   mrs r0, apsr
+  ; MCORE:   mrs r1, iapsr
+  ; MCORE:   mrs r1, eapsr
+  ; MCORE:   mrs r1, xpsr
+  ; MCORE:   mrs r1, ipsr
+  ; MCORE:   mrs r1, epsr
+  ; MCORE:   mrs r1, iepsr
+  ; MCORE:   mrs r1, msp
+  ; MCORE:   mrs r1, psp
+  ; MCORE:   mrs r1, primask
+  ; MCORE:   mrs r1, basepri
+  ; MCORE:   mrs r1, basepri_max
+  ; MCORE:   mrs r1, faultmask
+  ; MCORE:   mrs r1, control
+
+  %0 = call i32 @llvm.read_register.i32(metadata !0)
+  %1 = call i32 @llvm.read_register.i32(metadata !4)
+  %add1 = add i32 %1, %0
+  %2 = call i32 @llvm.read_register.i32(metadata !8)
+  %add2 = add i32 %add1, %2
+  %3 = call i32 @llvm.read_register.i32(metadata !12)
+  %add3 = add i32 %add2, %3
+  %4 = call i32 @llvm.read_register.i32(metadata !16)
+  %add4 = add i32 %add3, %4
+  %5 = call i32 @llvm.read_register.i32(metadata !17)
+  %add5 = add i32 %add4, %5
+  %6 = call i32 @llvm.read_register.i32(metadata !18)
+  %add6 = add i32 %add5, %6
+  %7 = call i32 @llvm.read_register.i32(metadata !19)
+  %add7 = add i32 %add6, %7
+  %8 = call i32 @llvm.read_register.i32(metadata !20)
+  %add8 = add i32 %add7, %8
+  %9 = call i32 @llvm.read_register.i32(metadata !21)
+  %add9 = add i32 %add8, %9
+  %10 = call i32 @llvm.read_register.i32(metadata !22)
+  %add10 = add i32 %add9, %10
+  %11 = call i32 @llvm.read_register.i32(metadata !23)
+  %add11 = add i32 %add10, %11
+  %12 = call i32 @llvm.read_register.i32(metadata !24)
+  %add12 = add i32 %add11, %12
+  %13 = call i32 @llvm.read_register.i32(metadata !25)
+  %add13 = add i32 %add12, %13
+  ret i32 %add13
+}
+
+define void @write_mclass_registers(i32 %x) nounwind {
+entry:
+  ; MCORE-LABEL: write_mclass_registers:
+  ; MCORE:   msr apsr_nzcvqg, r0
+  ; MCORE:   msr apsr_nzcvq, r0
+  ; MCORE:   msr apsr_g, r0
+  ; MCORE:   msr apsr_nzcvqg, r0
+  ; MCORE:   msr iapsr_nzcvqg, r0
+  ; MCORE:   msr iapsr_nzcvq, r0
+  ; MCORE:   msr iapsr_g, r0
+  ; MCORE:   msr iapsr_nzcvqg, r0
+  ; MCORE:   msr eapsr_nzcvqg, r0
+  ; MCORE:   msr eapsr_nzcvq, r0
+  ; MCORE:   msr eapsr_g, r0
+  ; MCORE:   msr eapsr_nzcvqg, r0
+  ; MCORE:   msr xpsr_nzcvqg, r0
+  ; MCORE:   msr xpsr_nzcvq, r0
+  ; MCORE:   msr xpsr_g, r0
+  ; MCORE:   msr xpsr_nzcvqg, r0
+  ; MCORE:   msr ipsr, r0
+  ; MCORE:   msr epsr, r0
+  ; MCORE:   msr iepsr, r0
+  ; MCORE:   msr msp, r0
+  ; MCORE:   msr psp, r0
+  ; MCORE:   msr primask, r0
+  ; MCORE:   msr basepri, r0
+  ; MCORE:   msr basepri_max, r0
+  ; MCORE:   msr faultmask, r0
+  ; MCORE:   msr control, r0
+
+  call void @llvm.write_register.i32(metadata !0, i32 %x)
+  call void @llvm.write_register.i32(metadata !1, i32 %x)
+  call void @llvm.write_register.i32(metadata !2, i32 %x)
+  call void @llvm.write_register.i32(metadata !3, i32 %x)
+  call void @llvm.write_register.i32(metadata !4, i32 %x)
+  call void @llvm.write_register.i32(metadata !5, i32 %x)
+  call void @llvm.write_register.i32(metadata !6, i32 %x)
+  call void @llvm.write_register.i32(metadata !7, i32 %x)
+  call void @llvm.write_register.i32(metadata !8, i32 %x)
+  call void @llvm.write_register.i32(metadata !9, i32 %x)
+  call void @llvm.write_register.i32(metadata !10, i32 %x)
+  call void @llvm.write_register.i32(metadata !11, i32 %x)
+  call void @llvm.write_register.i32(metadata !12, i32 %x)
+  call void @llvm.write_register.i32(metadata !13, i32 %x)
+  call void @llvm.write_register.i32(metadata !14, i32 %x)
+  call void @llvm.write_register.i32(metadata !15, i32 %x)
+  call void @llvm.write_register.i32(metadata !16, i32 %x)
+  call void @llvm.write_register.i32(metadata !17, i32 %x)
+  call void @llvm.write_register.i32(metadata !18, i32 %x)
+  call void @llvm.write_register.i32(metadata !19, i32 %x)
+  call void @llvm.write_register.i32(metadata !20, i32 %x)
+  call void @llvm.write_register.i32(metadata !21, i32 %x)
+  call void @llvm.write_register.i32(metadata !22, i32 %x)
+  call void @llvm.write_register.i32(metadata !23, i32 %x)
+  call void @llvm.write_register.i32(metadata !24, i32 %x)
+  call void @llvm.write_register.i32(metadata !25, i32 %x)
+  ret void
+}
+
+declare i32 @llvm.read_register.i32(metadata) nounwind
+declare void @llvm.write_register.i32(metadata, i32) nounwind
+
+!0 = !{!"apsr"}
+!1 = !{!"apsr_nzcvq"}
+!2 = !{!"apsr_g"}
+!3 = !{!"apsr_nzcvqg"}
+!4 = !{!"iapsr"}
+!5 = !{!"iapsr_nzcvq"}
+!6 = !{!"iapsr_g"}
+!7 = !{!"iapsr_nzcvqg"}
+!8 = !{!"eapsr"}
+!9 = !{!"eapsr_nzcvq"}
+!10 = !{!"eapsr_g"}
+!11 = !{!"eapsr_nzcvqg"}
+!12 = !{!"xpsr"}
+!13 = !{!"xpsr_nzcvq"}
+!14 = !{!"xpsr_g"}
+!15 = !{!"xpsr_nzcvqg"}
+!16 = !{!"ipsr"}
+!17 = !{!"epsr"}
+!18 = !{!"iepsr"}
+!19 = !{!"msp"}
+!20 = !{!"psp"}
+!21 = !{!"primask"}
+!22 = !{!"basepri"}
+!23 = !{!"basepri_max"}
+!24 = !{!"faultmask"}
+!25 = !{!"control"}

test/CodeGen/ARM/special-reg.ll

@@ -0,0 +1,78 @@
+; RUN: llc < %s -mtriple=arm-none-eabi -mcpu=cortex-a8 2>&1 | FileCheck %s --check-prefix=ARM --check-prefix=ACORE
+; RUN: llc < %s -mtriple=thumb-none-eabi -mcpu=cortex-m4 2>&1 | FileCheck %s --check-prefix=ARM --check-prefix=MCORE
+
+define i32 @read_i32_encoded_register() nounwind {
+entry:
+; ARM-LABEL: read_i32_encoded_register:
+; ARM: mrc p1, #2, r0, c3, c4, #5
+  %reg = call i32 @llvm.read_register.i32(metadata !0)
+  ret i32 %reg
+}
+
+define i64 @read_i64_encoded_register() nounwind {
+entry:
+; ARM-LABEL: read_i64_encoded_register:
+; ARM: mrrc p1, #2, r0, r1, c3
+  %reg = call i64 @llvm.read_register.i64(metadata !1)
+  ret i64 %reg
+}
+
+define i32 @read_apsr() nounwind {
+entry:
+; ARM-LABEL: read_apsr:
+; ARM: mrs r0, apsr
+  %reg = call i32 @llvm.read_register.i32(metadata !2)
+  ret i32 %reg
+}
+
+define i32 @read_fpscr() nounwind {
+entry:
+; ARM-LABEL: read_fpscr:
+; ARM: vmrs r0, fpscr
+  %reg = call i32 @llvm.read_register.i32(metadata !3)
+  ret i32 %reg
+}
+
+define void @write_i32_encoded_register(i32 %x) nounwind {
+entry:
+; ARM-LABEL: write_i32_encoded_register:
+; ARM: mcr p1, #2, r0, c3, c4, #5
+  call void @llvm.write_register.i32(metadata !0, i32 %x)
+  ret void
+}
+
+define void @write_i64_encoded_register(i64 %x) nounwind {
+entry:
+; ARM-LABEL: write_i64_encoded_register:
+; ARM: mcrr p1, #2, r0, r1, c3
+  call void @llvm.write_register.i64(metadata !1, i64 %x)
+  ret void
+}
+
+define void @write_apsr(i32 %x) nounwind {
+entry:
+; ARM-LABEL: write_apsr:
+; ACORE: msr APSR_nzcvq, r0
+; MCORE: msr apsr_nzcvq, r0
+  call void @llvm.write_register.i32(metadata !4, i32 %x)
+  ret void
+}
+
+define void @write_fpscr(i32 %x) nounwind {
+entry:
+; ARM-LABEL: write_fpscr:
+; ARM: vmsr fpscr, r0
+  call void @llvm.write_register.i32(metadata !3, i32 %x)
+  ret void
+}
+
+declare i32 @llvm.read_register.i32(metadata) nounwind
+declare i64 @llvm.read_register.i64(metadata) nounwind
+declare void @llvm.write_register.i32(metadata, i32) nounwind
+declare void @llvm.write_register.i64(metadata, i64) nounwind
+
+!0 = !{!"cp1:2:c3:c4:5"}
+!1 = !{!"cp1:2:c3"}
+!2 = !{!"apsr"}
+!3 = !{!"fpscr"}
+!4 = !{!"apsr_nzcvq"}