#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
#include "llvm/ADT/VectorExtras.h"
using namespace llvm;
TargetLowering(tm), Subtarget(*tm.getSubtargetImpl()), TM(tm) {
// Set up the register classes.
- addRegisterClass(MVT::i16, MSP430::MSP430RegsRegisterClass);
+ addRegisterClass(MVT::i8, MSP430::GR8RegisterClass);
+ addRegisterClass(MVT::i16, MSP430::GR16RegisterClass);
// Compute derived properties from the register classes
computeRegisterProperties();
- setOperationAction(ISD::RET, MVT::Other, Custom);
+ // Provide all sorts of operation actions
+
+ // Division is expensive
+ setIntDivIsCheap(false);
+
+ // Even if we have only 1 bit shift here, we can perform
+ // shifts of the whole bitwidth 1 bit per step.
+ setShiftAmountType(MVT::i8);
+
+ setStackPointerRegisterToSaveRestore(MSP430::SPW);
+ setBooleanContents(ZeroOrOneBooleanContent);
+ setSchedulingPreference(SchedulingForLatency);
+
+ setLoadExtAction(ISD::EXTLOAD, MVT::i1, Promote);
+ setLoadExtAction(ISD::SEXTLOAD, MVT::i1, Promote);
+ setLoadExtAction(ISD::ZEXTLOAD, MVT::i1, Promote);
+ setLoadExtAction(ISD::SEXTLOAD, MVT::i8, Expand);
+ setLoadExtAction(ISD::SEXTLOAD, MVT::i16, Expand);
+
+ // We don't have any truncstores
+ setTruncStoreAction(MVT::i16, MVT::i8, Expand);
+
+ setOperationAction(ISD::SRA, MVT::i8, Custom);
+ setOperationAction(ISD::SHL, MVT::i8, Custom);
+ setOperationAction(ISD::SRL, MVT::i8, Custom);
+ setOperationAction(ISD::SRA, MVT::i16, Custom);
+ setOperationAction(ISD::SHL, MVT::i16, Custom);
+ setOperationAction(ISD::SRL, MVT::i16, Custom);
+ setOperationAction(ISD::ROTL, MVT::i8, Expand);
+ setOperationAction(ISD::ROTR, MVT::i8, Expand);
+ setOperationAction(ISD::ROTL, MVT::i16, Expand);
+ setOperationAction(ISD::ROTR, MVT::i16, Expand);
+ setOperationAction(ISD::RET, MVT::Other, Custom);
+ setOperationAction(ISD::GlobalAddress, MVT::i16, Custom);
+ setOperationAction(ISD::ExternalSymbol, MVT::i16, Custom);
+ setOperationAction(ISD::BR_JT, MVT::Other, Expand);
+ setOperationAction(ISD::BRIND, MVT::Other, Expand);
+ setOperationAction(ISD::BR_CC, MVT::i8, Custom);
+ setOperationAction(ISD::BR_CC, MVT::i16, Custom);
+ setOperationAction(ISD::BRCOND, MVT::Other, Expand);
+ setOperationAction(ISD::SETCC, MVT::i8, Expand);
+ setOperationAction(ISD::SETCC, MVT::i16, Expand);
+ setOperationAction(ISD::SELECT, MVT::i8, Expand);
+ setOperationAction(ISD::SELECT, MVT::i16, Expand);
+ setOperationAction(ISD::SELECT_CC, MVT::i8, Custom);
+ setOperationAction(ISD::SELECT_CC, MVT::i16, Custom);
+ setOperationAction(ISD::SIGN_EXTEND, MVT::i16, Custom);
+
+ // FIXME: Implement efficiently multiplication by a constant
+ setOperationAction(ISD::MUL, MVT::i16, Expand);
+ setOperationAction(ISD::MULHS, MVT::i16, Expand);
+ setOperationAction(ISD::MULHU, MVT::i16, Expand);
+ setOperationAction(ISD::SMUL_LOHI, MVT::i16, Expand);
+ setOperationAction(ISD::UMUL_LOHI, MVT::i16, Expand);
+
+ setOperationAction(ISD::UDIV, MVT::i16, Expand);
+ setOperationAction(ISD::UDIVREM, MVT::i16, Expand);
+ setOperationAction(ISD::UREM, MVT::i16, Expand);
+ setOperationAction(ISD::SDIV, MVT::i16, Expand);
+ setOperationAction(ISD::SDIVREM, MVT::i16, Expand);
+ setOperationAction(ISD::SREM, MVT::i16, Expand);
}
-SDValue MSP430TargetLowering::
-LowerOperation(SDValue Op, SelectionDAG &DAG) {
+SDValue MSP430TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) {
switch (Op.getOpcode()) {
case ISD::FORMAL_ARGUMENTS: return LowerFORMAL_ARGUMENTS(Op, DAG);
- case ISD::RET: return LowerRET(Op, DAG);
+ case ISD::SHL: // FALLTHROUGH
+ case ISD::SRL:
+ case ISD::SRA: return LowerShifts(Op, DAG);
+ case ISD::RET: return LowerRET(Op, DAG);
+ case ISD::CALL: return LowerCALL(Op, DAG);
+ case ISD::GlobalAddress: return LowerGlobalAddress(Op, DAG);
+ case ISD::ExternalSymbol: return LowerExternalSymbol(Op, DAG);
+ case ISD::BR_CC: return LowerBR_CC(Op, DAG);
+ case ISD::SELECT_CC: return LowerSELECT_CC(Op, DAG);
+ case ISD::SIGN_EXTEND: return LowerSIGN_EXTEND(Op, DAG);
default:
- assert(0 && "unimplemented operand");
+ llvm_unreachable("unimplemented operand");
return SDValue();
}
}
+/// getFunctionAlignment - Return the Log2 alignment of this function.
+unsigned MSP430TargetLowering::getFunctionAlignment(const Function *F) const {
+ return F->hasFnAttr(Attribute::OptimizeForSize) ? 1 : 4;
+}
+
//===----------------------------------------------------------------------===//
// Calling Convention Implementation
//===----------------------------------------------------------------------===//
unsigned CC = cast<ConstantSDNode>(Op.getOperand(1))->getZExtValue();
switch (CC) {
default:
- assert(0 && "Unsupported calling convention");
+ llvm_unreachable("Unsupported calling convention");
case CallingConv::C:
case CallingConv::Fast:
return LowerCCCArguments(Op, DAG);
}
}
+SDValue MSP430TargetLowering::LowerCALL(SDValue Op, SelectionDAG &DAG) {
+ CallSDNode *TheCall = cast<CallSDNode>(Op.getNode());
+ unsigned CallingConv = TheCall->getCallingConv();
+ switch (CallingConv) {
+ default:
+ llvm_unreachable("Unsupported calling convention");
+ case CallingConv::Fast:
+ case CallingConv::C:
+ return LowerCCCCallTo(Op, DAG, CallingConv);
+ }
+}
+
/// LowerCCCArguments - transform physical registers into virtual registers and
/// generate load operations for arguments places on the stack.
// FIXME: struct return stuff
// Assign locations to all of the incoming arguments.
SmallVector<CCValAssign, 16> ArgLocs;
- CCState CCInfo(CC, isVarArg, getTargetMachine(), ArgLocs);
+ CCState CCInfo(CC, isVarArg, getTargetMachine(), ArgLocs, DAG.getContext());
CCInfo.AnalyzeFormalArguments(Op.getNode(), CC_MSP430);
assert(!isVarArg && "Varargs not supported yet");
// Arguments passed in registers
MVT RegVT = VA.getLocVT();
switch (RegVT.getSimpleVT()) {
- default:
- cerr << "LowerFORMAL_ARGUMENTS Unhandled argument type: "
- << RegVT.getSimpleVT()
- << "\n";
- abort();
+ default:
+ {
+#ifndef NDEBUG
+ cerr << "LowerFORMAL_ARGUMENTS Unhandled argument type: "
+ << RegVT.getSimpleVT() << "\n";
+#endif
+ llvm_unreachable(0);
+ }
case MVT::i16:
unsigned VReg =
- RegInfo.createVirtualRegister(MSP430::MSP430RegsRegisterClass);
+ RegInfo.createVirtualRegister(MSP430::GR16RegisterClass);
RegInfo.addLiveIn(VA.getLocReg(), VReg);
SDValue ArgValue = DAG.getCopyFromReg(Root, dl, VReg, RegVT);
DebugLoc dl = Op.getDebugLoc();
// CCState - Info about the registers and stack slot.
- CCState CCInfo(CC, isVarArg, getTargetMachine(), RVLocs);
+ CCState CCInfo(CC, isVarArg, getTargetMachine(), RVLocs, DAG.getContext());
// Analize return values of ISD::RET
CCInfo.AnalyzeReturn(Op.getNode(), RetCC_MSP430);
return DAG.getNode(MSP430ISD::RET_FLAG, dl, MVT::Other, Chain);
}
+/// LowerCCCCallTo - functions arguments are copied from virtual regs to
+/// (physical regs)/(stack frame), CALLSEQ_START and CALLSEQ_END are emitted.
+/// TODO: sret.
+SDValue MSP430TargetLowering::LowerCCCCallTo(SDValue Op, SelectionDAG &DAG,
+ unsigned CC) {
+ CallSDNode *TheCall = cast<CallSDNode>(Op.getNode());
+ SDValue Chain = TheCall->getChain();
+ SDValue Callee = TheCall->getCallee();
+ bool isVarArg = TheCall->isVarArg();
+ DebugLoc dl = Op.getDebugLoc();
+
+ // Analyze operands of the call, assigning locations to each operand.
+ SmallVector<CCValAssign, 16> ArgLocs;
+ CCState CCInfo(CC, isVarArg, getTargetMachine(), ArgLocs, DAG.getContext());
+
+ CCInfo.AnalyzeCallOperands(TheCall, CC_MSP430);
+
+ // Get a count of how many bytes are to be pushed on the stack.
+ unsigned NumBytes = CCInfo.getNextStackOffset();
+
+ Chain = DAG.getCALLSEQ_START(Chain ,DAG.getConstant(NumBytes,
+ getPointerTy(), true));
+
+ SmallVector<std::pair<unsigned, SDValue>, 4> RegsToPass;
+ SmallVector<SDValue, 12> MemOpChains;
+ SDValue StackPtr;
+
+ // Walk the register/memloc assignments, inserting copies/loads.
+ for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
+ CCValAssign &VA = ArgLocs[i];
+
+ // Arguments start after the 5 first operands of ISD::CALL
+ SDValue Arg = TheCall->getArg(i);
+
+ // Promote the value if needed.
+ switch (VA.getLocInfo()) {
+ default: llvm_unreachable("Unknown loc info!");
+ case CCValAssign::Full: break;
+ case CCValAssign::SExt:
+ Arg = DAG.getNode(ISD::SIGN_EXTEND, dl, VA.getLocVT(), Arg);
+ break;
+ case CCValAssign::ZExt:
+ Arg = DAG.getNode(ISD::ZERO_EXTEND, dl, VA.getLocVT(), Arg);
+ break;
+ case CCValAssign::AExt:
+ Arg = DAG.getNode(ISD::ANY_EXTEND, dl, VA.getLocVT(), Arg);
+ break;
+ }
+
+ // Arguments that can be passed on register must be kept at RegsToPass
+ // vector
+ if (VA.isRegLoc()) {
+ RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
+ } else {
+ assert(VA.isMemLoc());
+
+ if (StackPtr.getNode() == 0)
+ StackPtr = DAG.getCopyFromReg(Chain, dl, MSP430::SPW, getPointerTy());
+
+ SDValue PtrOff = DAG.getNode(ISD::ADD, dl, getPointerTy(),
+ StackPtr,
+ DAG.getIntPtrConstant(VA.getLocMemOffset()));
+
+
+ MemOpChains.push_back(DAG.getStore(Chain, dl, Arg, PtrOff,
+ PseudoSourceValue::getStack(),
+ VA.getLocMemOffset()));
+ }
+ }
+
+ // Transform all store nodes into one single node because all store nodes are
+ // independent of each other.
+ if (!MemOpChains.empty())
+ Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
+ &MemOpChains[0], MemOpChains.size());
+
+ // Build a sequence of copy-to-reg nodes chained together with token chain and
+ // flag operands which copy the outgoing args into registers. The InFlag in
+ // necessary since all emited instructions must be stuck together.
+ SDValue InFlag;
+ for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
+ Chain = DAG.getCopyToReg(Chain, dl, RegsToPass[i].first,
+ RegsToPass[i].second, InFlag);
+ InFlag = Chain.getValue(1);
+ }
+
+ // If the callee is a GlobalAddress node (quite common, every direct call is)
+ // turn it into a TargetGlobalAddress node so that legalize doesn't hack it.
+ // Likewise ExternalSymbol -> TargetExternalSymbol.
+ if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
+ Callee = DAG.getTargetGlobalAddress(G->getGlobal(), MVT::i16);
+ else if (ExternalSymbolSDNode *E = dyn_cast<ExternalSymbolSDNode>(Callee))
+ Callee = DAG.getTargetExternalSymbol(E->getSymbol(), MVT::i16);
+
+ // Returns a chain & a flag for retval copy to use.
+ SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Flag);
+ SmallVector<SDValue, 8> Ops;
+ Ops.push_back(Chain);
+ Ops.push_back(Callee);
+
+ // Add argument registers to the end of the list so that they are
+ // known live into the call.
+ for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i)
+ Ops.push_back(DAG.getRegister(RegsToPass[i].first,
+ RegsToPass[i].second.getValueType()));
+
+ if (InFlag.getNode())
+ Ops.push_back(InFlag);
+
+ Chain = DAG.getNode(MSP430ISD::CALL, dl, NodeTys, &Ops[0], Ops.size());
+ InFlag = Chain.getValue(1);
+
+ // Create the CALLSEQ_END node.
+ Chain = DAG.getCALLSEQ_END(Chain,
+ DAG.getConstant(NumBytes, getPointerTy(), true),
+ DAG.getConstant(0, getPointerTy(), true),
+ InFlag);
+ InFlag = Chain.getValue(1);
+
+ // Handle result values, copying them out of physregs into vregs that we
+ // return.
+ return SDValue(LowerCallResult(Chain, InFlag, TheCall, CC, DAG),
+ Op.getResNo());
+}
+
+/// LowerCallResult - Lower the result values of an ISD::CALL into the
+/// appropriate copies out of appropriate physical registers. This assumes that
+/// Chain/InFlag are the input chain/flag to use, and that TheCall is the call
+/// being lowered. Returns a SDNode with the same number of values as the
+/// ISD::CALL.
+SDNode*
+MSP430TargetLowering::LowerCallResult(SDValue Chain, SDValue InFlag,
+ CallSDNode *TheCall,
+ unsigned CallingConv,
+ SelectionDAG &DAG) {
+ bool isVarArg = TheCall->isVarArg();
+ DebugLoc dl = TheCall->getDebugLoc();
+
+ // Assign locations to each value returned by this call.
+ SmallVector<CCValAssign, 16> RVLocs;
+ CCState CCInfo(CallingConv, isVarArg, getTargetMachine(),
+ RVLocs, DAG.getContext());
+
+ CCInfo.AnalyzeCallResult(TheCall, RetCC_MSP430);
+ SmallVector<SDValue, 8> ResultVals;
+
+ // Copy all of the result registers out of their specified physreg.
+ for (unsigned i = 0; i != RVLocs.size(); ++i) {
+ Chain = DAG.getCopyFromReg(Chain, dl, RVLocs[i].getLocReg(),
+ RVLocs[i].getValVT(), InFlag).getValue(1);
+ InFlag = Chain.getValue(2);
+ ResultVals.push_back(Chain.getValue(0));
+ }
+
+ ResultVals.push_back(Chain);
+
+ // Merge everything together with a MERGE_VALUES node.
+ return DAG.getNode(ISD::MERGE_VALUES, dl, TheCall->getVTList(),
+ &ResultVals[0], ResultVals.size()).getNode();
+}
+
+SDValue MSP430TargetLowering::LowerShifts(SDValue Op,
+ SelectionDAG &DAG) {
+ unsigned Opc = Op.getOpcode();
+ SDNode* N = Op.getNode();
+ MVT VT = Op.getValueType();
+ DebugLoc dl = N->getDebugLoc();
+
+ // We currently only lower shifts of constant argument.
+ if (!isa<ConstantSDNode>(N->getOperand(1)))
+ return SDValue();
+
+ uint64_t ShiftAmount = cast<ConstantSDNode>(N->getOperand(1))->getZExtValue();
+
+ // Expand the stuff into sequence of shifts.
+ // FIXME: for some shift amounts this might be done better!
+ // E.g.: foo >> (8 + N) => sxt(swpb(foo)) >> N
+ SDValue Victim = N->getOperand(0);
+
+ if (Opc == ISD::SRL && ShiftAmount) {
+ // Emit a special goodness here:
+ // srl A, 1 => clrc; rrc A
+ Victim = DAG.getNode(MSP430ISD::RRC, dl, VT, Victim);
+ ShiftAmount -= 1;
+ }
+
+ while (ShiftAmount--)
+ Victim = DAG.getNode((Opc == ISD::SHL ? MSP430ISD::RLA : MSP430ISD::RRA),
+ dl, VT, Victim);
+
+ return Victim;
+}
+
+SDValue MSP430TargetLowering::LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) {
+ const GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
+ int64_t Offset = cast<GlobalAddressSDNode>(Op)->getOffset();
+
+ // Create the TargetGlobalAddress node, folding in the constant offset.
+ SDValue Result = DAG.getTargetGlobalAddress(GV, getPointerTy(), Offset);
+ return DAG.getNode(MSP430ISD::Wrapper, Op.getDebugLoc(),
+ getPointerTy(), Result);
+}
+
+SDValue MSP430TargetLowering::LowerExternalSymbol(SDValue Op,
+ SelectionDAG &DAG) {
+ DebugLoc dl = Op.getDebugLoc();
+ const char *Sym = cast<ExternalSymbolSDNode>(Op)->getSymbol();
+ SDValue Result = DAG.getTargetExternalSymbol(Sym, getPointerTy());
+
+ return DAG.getNode(MSP430ISD::Wrapper, dl, getPointerTy(), Result);;
+}
+
+static SDValue EmitCMP(SDValue &LHS, SDValue &RHS, unsigned &TargetCC,
+ ISD::CondCode CC,
+ DebugLoc dl, SelectionDAG &DAG) {
+ // FIXME: Handle bittests someday
+ assert(!LHS.getValueType().isFloatingPoint() && "We don't handle FP yet");
+
+ // FIXME: Handle jump negative someday
+ TargetCC = MSP430::COND_INVALID;
+ switch (CC) {
+ default: llvm_unreachable("Invalid integer condition!");
+ case ISD::SETEQ:
+ TargetCC = MSP430::COND_E; // aka COND_Z
+ break;
+ case ISD::SETNE:
+ TargetCC = MSP430::COND_NE; // aka COND_NZ
+ break;
+ case ISD::SETULE:
+ std::swap(LHS, RHS); // FALLTHROUGH
+ case ISD::SETUGE:
+ TargetCC = MSP430::COND_HS; // aka COND_C
+ break;
+ case ISD::SETUGT:
+ std::swap(LHS, RHS); // FALLTHROUGH
+ case ISD::SETULT:
+ TargetCC = MSP430::COND_LO; // aka COND_NC
+ break;
+ case ISD::SETLE:
+ std::swap(LHS, RHS); // FALLTHROUGH
+ case ISD::SETGE:
+ TargetCC = MSP430::COND_GE;
+ break;
+ case ISD::SETGT:
+ std::swap(LHS, RHS); // FALLTHROUGH
+ case ISD::SETLT:
+ TargetCC = MSP430::COND_L;
+ break;
+ }
+
+ return DAG.getNode(MSP430ISD::CMP, dl, MVT::Flag, LHS, RHS);
+}
+
+
+SDValue MSP430TargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) {
+ SDValue Chain = Op.getOperand(0);
+ ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(1))->get();
+ SDValue LHS = Op.getOperand(2);
+ SDValue RHS = Op.getOperand(3);
+ SDValue Dest = Op.getOperand(4);
+ DebugLoc dl = Op.getDebugLoc();
+
+ unsigned TargetCC = MSP430::COND_INVALID;
+ SDValue Flag = EmitCMP(LHS, RHS, TargetCC, CC, dl, DAG);
+
+ return DAG.getNode(MSP430ISD::BR_CC, dl, Op.getValueType(),
+ Chain,
+ Dest, DAG.getConstant(TargetCC, MVT::i8),
+ Flag);
+}
+
+SDValue MSP430TargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) {
+ SDValue LHS = Op.getOperand(0);
+ SDValue RHS = Op.getOperand(1);
+ SDValue TrueV = Op.getOperand(2);
+ SDValue FalseV = Op.getOperand(3);
+ ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
+ DebugLoc dl = Op.getDebugLoc();
+
+ unsigned TargetCC = MSP430::COND_INVALID;
+ SDValue Flag = EmitCMP(LHS, RHS, TargetCC, CC, dl, DAG);
+
+ SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Flag);
+ SmallVector<SDValue, 4> Ops;
+ Ops.push_back(TrueV);
+ Ops.push_back(FalseV);
+ Ops.push_back(DAG.getConstant(TargetCC, MVT::i8));
+ Ops.push_back(Flag);
+
+ return DAG.getNode(MSP430ISD::SELECT_CC, dl, VTs, &Ops[0], Ops.size());
+}
+
+SDValue MSP430TargetLowering::LowerSIGN_EXTEND(SDValue Op,
+ SelectionDAG &DAG) {
+ SDValue Val = Op.getOperand(0);
+ MVT VT = Op.getValueType();
+ DebugLoc dl = Op.getDebugLoc();
+
+ assert(VT == MVT::i16 && "Only support i16 for now!");
+
+ return DAG.getNode(ISD::SIGN_EXTEND_INREG, dl, VT,
+ DAG.getNode(ISD::ANY_EXTEND, dl, VT, Val),
+ DAG.getValueType(Val.getValueType()));
+}
+
const char *MSP430TargetLowering::getTargetNodeName(unsigned Opcode) const {
switch (Opcode) {
default: return NULL;
case MSP430ISD::RET_FLAG: return "MSP430ISD::RET_FLAG";
+ case MSP430ISD::RRA: return "MSP430ISD::RRA";
+ case MSP430ISD::RLA: return "MSP430ISD::RLA";
+ case MSP430ISD::RRC: return "MSP430ISD::RRC";
+ case MSP430ISD::CALL: return "MSP430ISD::CALL";
+ case MSP430ISD::Wrapper: return "MSP430ISD::Wrapper";
+ case MSP430ISD::BR_CC: return "MSP430ISD::BR_CC";
+ case MSP430ISD::CMP: return "MSP430ISD::CMP";
+ case MSP430ISD::SELECT_CC: return "MSP430ISD::SELECT_CC";
}
}
+//===----------------------------------------------------------------------===//
+// Other Lowering Code
+//===----------------------------------------------------------------------===//
+
+MachineBasicBlock*
+MSP430TargetLowering::EmitInstrWithCustomInserter(MachineInstr *MI,
+ MachineBasicBlock *BB) const {
+ const TargetInstrInfo &TII = *getTargetMachine().getInstrInfo();
+ DebugLoc dl = MI->getDebugLoc();
+ assert((MI->getOpcode() == MSP430::Select16 ||
+ MI->getOpcode() == MSP430::Select8) &&
+ "Unexpected instr type to insert");
+
+ // To "insert" a SELECT instruction, we actually have to insert the diamond
+ // control-flow pattern. The incoming instruction knows the destination vreg
+ // to set, the condition code register to branch on, the true/false values to
+ // select between, and a branch opcode to use.
+ const BasicBlock *LLVM_BB = BB->getBasicBlock();
+ MachineFunction::iterator I = BB;
+ ++I;
+
+ // thisMBB:
+ // ...
+ // TrueVal = ...
+ // cmpTY ccX, r1, r2
+ // jCC copy1MBB
+ // fallthrough --> copy0MBB
+ MachineBasicBlock *thisMBB = BB;
+ MachineFunction *F = BB->getParent();
+ MachineBasicBlock *copy0MBB = F->CreateMachineBasicBlock(LLVM_BB);
+ MachineBasicBlock *copy1MBB = F->CreateMachineBasicBlock(LLVM_BB);
+ BuildMI(BB, dl, TII.get(MSP430::JCC))
+ .addMBB(copy1MBB)
+ .addImm(MI->getOperand(3).getImm());
+ F->insert(I, copy0MBB);
+ F->insert(I, copy1MBB);
+ // Update machine-CFG edges by transferring all successors of the current
+ // block to the new block which will contain the Phi node for the select.
+ copy1MBB->transferSuccessors(BB);
+ // Next, add the true and fallthrough blocks as its successors.
+ BB->addSuccessor(copy0MBB);
+ BB->addSuccessor(copy1MBB);
+
+ // copy0MBB:
+ // %FalseValue = ...
+ // # fallthrough to copy1MBB
+ BB = copy0MBB;
+
+ // Update machine-CFG edges
+ BB->addSuccessor(copy1MBB);
+
+ // copy1MBB:
+ // %Result = phi [ %FalseValue, copy0MBB ], [ %TrueValue, thisMBB ]
+ // ...
+ BB = copy1MBB;
+ BuildMI(BB, dl, TII.get(MSP430::PHI),
+ MI->getOperand(0).getReg())
+ .addReg(MI->getOperand(2).getReg()).addMBB(copy0MBB)
+ .addReg(MI->getOperand(1).getReg()).addMBB(thisMBB);
+
+ F->DeleteMachineInstr(MI); // The pseudo instruction is gone now.
+ return BB;
+}
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