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llvm-6502/lib/Target/MSP430/MSP430ISelLowering.cpp
Chandler Carruth 63974b2144 Initial CodeGen support for CTTZ/CTLZ where a zero input produces an 
undefined result. This adds new ISD nodes for the new semantics,
selecting them when the LLVM intrinsic indicates that the undef behavior
is desired. The new nodes expand trivially to the old nodes, so targets
don't actually need to do anything to support these new nodes besides
indicating that they should be expanded. I've done this for all the
operand types that I could figure out for all the targets. Owners of
various targets, please review and let me know if any of these are
incorrect.

Note that the expand behavior is *conservatively correct*, and exactly
matches LLVM's current behavior with these operations. Ideally this
patch will not change behavior in any way. For example the regtest suite
finds the exact same instruction sequences coming out of the code
generator. That's why there are no new tests here -- all of this is
being exercised by the existing test suite.

Thanks to Duncan Sands for reviewing the various bits of this patch and
helping me get the wrinkles ironed out with expanding for each target.
Also thanks to Chris for clarifying through all the discussions that
this is indeed the approach he was looking for. That said, there are
likely still rough spots. Further review much appreciated.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146466 91177308-0d34-0410-b5e6-96231b3b80d8
2011-12-13 01:56:10 +00:00

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//===-- MSP430ISelLowering.cpp - MSP430 DAG Lowering Implementation ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the MSP430TargetLowering class.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "msp430-lower"
#include "MSP430ISelLowering.h"
#include "MSP430.h"
#include "MSP430MachineFunctionInfo.h"
#include "MSP430TargetMachine.h"
#include "MSP430Subtarget.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Intrinsics.h"
#include "llvm/CallingConv.h"
#include "llvm/GlobalVariable.h"
#include "llvm/GlobalAlias.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/VectorExtras.h"
using namespace llvm;
typedef enum {
NoHWMult,
HWMultIntr,
HWMultNoIntr
} HWMultUseMode;
static cl::opt<HWMultUseMode>
HWMultMode("msp430-hwmult-mode",
cl::desc("Hardware multiplier use mode"),
cl::init(HWMultNoIntr),
cl::values(
clEnumValN(NoHWMult, "no",
"Do not use hardware multiplier"),
clEnumValN(HWMultIntr, "interrupts",
"Assume hardware multiplier can be used inside interrupts"),
clEnumValN(HWMultNoIntr, "use",
"Assume hardware multiplier cannot be used inside interrupts"),
clEnumValEnd));
MSP430TargetLowering::MSP430TargetLowering(MSP430TargetMachine &tm) :
TargetLowering(tm, new TargetLoweringObjectFileELF()),
Subtarget(*tm.getSubtargetImpl()), TM(tm) {
TD = getTargetData();
// Set up the register classes.
addRegisterClass(MVT::i8, MSP430::GR8RegisterClass);
addRegisterClass(MVT::i16, MSP430::GR16RegisterClass);
// Compute derived properties from the register classes
computeRegisterProperties();
// Provide all sorts of operation actions
// Division is expensive
setIntDivIsCheap(false);
setStackPointerRegisterToSaveRestore(MSP430::SPW);
setBooleanContents(ZeroOrOneBooleanContent);
setBooleanVectorContents(ZeroOrOneBooleanContent); // FIXME: Is this correct?
// We have post-incremented loads / stores.
setIndexedLoadAction(ISD::POST_INC, MVT::i8, Legal);
setIndexedLoadAction(ISD::POST_INC, MVT::i16, Legal);
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::GlobalAddress, MVT::i16, Custom);
setOperationAction(ISD::ExternalSymbol, MVT::i16, Custom);
setOperationAction(ISD::BlockAddress, MVT::i16, Custom);
setOperationAction(ISD::BR_JT, 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, Custom);
setOperationAction(ISD::SETCC, MVT::i16, Custom);
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);
setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i8, Expand);
setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i16, Expand);
setOperationAction(ISD::CTTZ, MVT::i8, Expand);
setOperationAction(ISD::CTTZ, MVT::i16, Expand);
setOperationAction(ISD::CTTZ_ZERO_UNDEF, MVT::i8, Expand);
setOperationAction(ISD::CTTZ_ZERO_UNDEF, MVT::i16, Expand);
setOperationAction(ISD::CTLZ, MVT::i8, Expand);
setOperationAction(ISD::CTLZ, MVT::i16, Expand);
setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i8, Expand);
setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i16, Expand);
setOperationAction(ISD::CTPOP, MVT::i8, Expand);
setOperationAction(ISD::CTPOP, MVT::i16, Expand);
setOperationAction(ISD::SHL_PARTS, MVT::i8, Expand);
setOperationAction(ISD::SHL_PARTS, MVT::i16, Expand);
setOperationAction(ISD::SRL_PARTS, MVT::i8, Expand);
setOperationAction(ISD::SRL_PARTS, MVT::i16, Expand);
setOperationAction(ISD::SRA_PARTS, MVT::i8, Expand);
setOperationAction(ISD::SRA_PARTS, MVT::i16, Expand);
setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);
// FIXME: Implement efficiently multiplication by a constant
setOperationAction(ISD::MUL, MVT::i8, Expand);
setOperationAction(ISD::MULHS, MVT::i8, Expand);
setOperationAction(ISD::MULHU, MVT::i8, Expand);
setOperationAction(ISD::SMUL_LOHI, MVT::i8, Expand);
setOperationAction(ISD::UMUL_LOHI, MVT::i8, Expand);
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::i8, Expand);
setOperationAction(ISD::UDIVREM, MVT::i8, Expand);
setOperationAction(ISD::UREM, MVT::i8, Expand);
setOperationAction(ISD::SDIV, MVT::i8, Expand);
setOperationAction(ISD::SDIVREM, MVT::i8, Expand);
setOperationAction(ISD::SREM, MVT::i8, 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);
// Libcalls names.
if (HWMultMode == HWMultIntr) {
setLibcallName(RTLIB::MUL_I8, "__mulqi3hw");
setLibcallName(RTLIB::MUL_I16, "__mulhi3hw");
} else if (HWMultMode == HWMultNoIntr) {
setLibcallName(RTLIB::MUL_I8, "__mulqi3hw_noint");
setLibcallName(RTLIB::MUL_I16, "__mulhi3hw_noint");
}
setMinFunctionAlignment(1);
setPrefFunctionAlignment(2);
}
SDValue MSP430TargetLowering::LowerOperation(SDValue Op,
SelectionDAG &DAG) const {
switch (Op.getOpcode()) {
case ISD::SHL: // FALLTHROUGH
case ISD::SRL:
case ISD::SRA: return LowerShifts(Op, DAG);
case ISD::GlobalAddress: return LowerGlobalAddress(Op, DAG);
case ISD::BlockAddress: return LowerBlockAddress(Op, DAG);
case ISD::ExternalSymbol: return LowerExternalSymbol(Op, DAG);
case ISD::SETCC: return LowerSETCC(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);
case ISD::RETURNADDR: return LowerRETURNADDR(Op, DAG);
case ISD::FRAMEADDR: return LowerFRAMEADDR(Op, DAG);
default:
llvm_unreachable("unimplemented operand");
return SDValue();
}
}
//===----------------------------------------------------------------------===//
// MSP430 Inline Assembly Support
//===----------------------------------------------------------------------===//
/// getConstraintType - Given a constraint letter, return the type of
/// constraint it is for this target.
TargetLowering::ConstraintType
MSP430TargetLowering::getConstraintType(const std::string &Constraint) const {
if (Constraint.size() == 1) {
switch (Constraint[0]) {
case 'r':
return C_RegisterClass;
default:
break;
}
}
return TargetLowering::getConstraintType(Constraint);
}
std::pair<unsigned, const TargetRegisterClass*>
MSP430TargetLowering::
getRegForInlineAsmConstraint(const std::string &Constraint,
EVT VT) const {
if (Constraint.size() == 1) {
// GCC Constraint Letters
switch (Constraint[0]) {
default: break;
case 'r': // GENERAL_REGS
if (VT == MVT::i8)
return std::make_pair(0U, MSP430::GR8RegisterClass);
return std::make_pair(0U, MSP430::GR16RegisterClass);
}
}
return TargetLowering::getRegForInlineAsmConstraint(Constraint, VT);
}
//===----------------------------------------------------------------------===//
// Calling Convention Implementation
//===----------------------------------------------------------------------===//
#include "MSP430GenCallingConv.inc"
SDValue
MSP430TargetLowering::LowerFormalArguments(SDValue Chain,
CallingConv::ID CallConv,
bool isVarArg,
const SmallVectorImpl<ISD::InputArg>
&Ins,
DebugLoc dl,
SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals)
const {
switch (CallConv) {
default:
llvm_unreachable("Unsupported calling convention");
case CallingConv::C:
case CallingConv::Fast:
return LowerCCCArguments(Chain, CallConv, isVarArg, Ins, dl, DAG, InVals);
case CallingConv::MSP430_INTR:
if (Ins.empty())
return Chain;
else {
report_fatal_error("ISRs cannot have arguments");
return SDValue();
}
}
}
SDValue
MSP430TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
CallingConv::ID CallConv, bool isVarArg,
bool &isTailCall,
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<SDValue> &OutVals,
const SmallVectorImpl<ISD::InputArg> &Ins,
DebugLoc dl, SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals) const {
// MSP430 target does not yet support tail call optimization.
isTailCall = false;
switch (CallConv) {
default:
llvm_unreachable("Unsupported calling convention");
case CallingConv::Fast:
case CallingConv::C:
return LowerCCCCallTo(Chain, Callee, CallConv, isVarArg, isTailCall,
Outs, OutVals, Ins, dl, DAG, InVals);
case CallingConv::MSP430_INTR:
report_fatal_error("ISRs cannot be called directly");
return SDValue();
}
}
/// LowerCCCArguments - transform physical registers into virtual registers and
/// generate load operations for arguments places on the stack.
// FIXME: struct return stuff
// FIXME: varargs
SDValue
MSP430TargetLowering::LowerCCCArguments(SDValue Chain,
CallingConv::ID CallConv,
bool isVarArg,
const SmallVectorImpl<ISD::InputArg>
&Ins,
DebugLoc dl,
SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals)
const {
MachineFunction &MF = DAG.getMachineFunction();
MachineFrameInfo *MFI = MF.getFrameInfo();
MachineRegisterInfo &RegInfo = MF.getRegInfo();
// Assign locations to all of the incoming arguments.
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(),
getTargetMachine(), ArgLocs, *DAG.getContext());
CCInfo.AnalyzeFormalArguments(Ins, CC_MSP430);
assert(!isVarArg && "Varargs not supported yet");
for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
CCValAssign &VA = ArgLocs[i];
if (VA.isRegLoc()) {
// Arguments passed in registers
EVT RegVT = VA.getLocVT();
switch (RegVT.getSimpleVT().SimpleTy) {
default:
{
#ifndef NDEBUG
errs() << "LowerFormalArguments Unhandled argument type: "
<< RegVT.getSimpleVT().SimpleTy << "\n";
#endif
llvm_unreachable(0);
}
case MVT::i16:
unsigned VReg =
RegInfo.createVirtualRegister(MSP430::GR16RegisterClass);
RegInfo.addLiveIn(VA.getLocReg(), VReg);
SDValue ArgValue = DAG.getCopyFromReg(Chain, dl, VReg, RegVT);
// If this is an 8-bit value, it is really passed promoted to 16
// bits. Insert an assert[sz]ext to capture this, then truncate to the
// right size.
if (VA.getLocInfo() == CCValAssign::SExt)
ArgValue = DAG.getNode(ISD::AssertSext, dl, RegVT, ArgValue,
DAG.getValueType(VA.getValVT()));
else if (VA.getLocInfo() == CCValAssign::ZExt)
ArgValue = DAG.getNode(ISD::AssertZext, dl, RegVT, ArgValue,
DAG.getValueType(VA.getValVT()));
if (VA.getLocInfo() != CCValAssign::Full)
ArgValue = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), ArgValue);
InVals.push_back(ArgValue);
}
} else {
// Sanity check
assert(VA.isMemLoc());
// Load the argument to a virtual register
unsigned ObjSize = VA.getLocVT().getSizeInBits()/8;
if (ObjSize > 2) {
errs() << "LowerFormalArguments Unhandled argument type: "
<< EVT(VA.getLocVT()).getEVTString()
<< "\n";
}
// Create the frame index object for this incoming parameter...
int FI = MFI->CreateFixedObject(ObjSize, VA.getLocMemOffset(), true);
// Create the SelectionDAG nodes corresponding to a load
//from this parameter
SDValue FIN = DAG.getFrameIndex(FI, MVT::i16);
InVals.push_back(DAG.getLoad(VA.getLocVT(), dl, Chain, FIN,
MachinePointerInfo::getFixedStack(FI),
false, false, false, 0));
}
}
return Chain;
}
SDValue
MSP430TargetLowering::LowerReturn(SDValue Chain,
CallingConv::ID CallConv, bool isVarArg,
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<SDValue> &OutVals,
DebugLoc dl, SelectionDAG &DAG) const {
// CCValAssign - represent the assignment of the return value to a location
SmallVector<CCValAssign, 16> RVLocs;
// ISRs cannot return any value.
if (CallConv == CallingConv::MSP430_INTR && !Outs.empty()) {
report_fatal_error("ISRs cannot return any value");
return SDValue();
}
// CCState - Info about the registers and stack slot.
CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(),
getTargetMachine(), RVLocs, *DAG.getContext());
// Analize return values.
CCInfo.AnalyzeReturn(Outs, RetCC_MSP430);
// If this is the first return lowered for this function, add the regs to the
// liveout set for the function.
if (DAG.getMachineFunction().getRegInfo().liveout_empty()) {
for (unsigned i = 0; i != RVLocs.size(); ++i)
if (RVLocs[i].isRegLoc())
DAG.getMachineFunction().getRegInfo().addLiveOut(RVLocs[i].getLocReg());
}
SDValue Flag;
// Copy the result values into the output registers.
for (unsigned i = 0; i != RVLocs.size(); ++i) {
CCValAssign &VA = RVLocs[i];
assert(VA.isRegLoc() && "Can only return in registers!");
Chain = DAG.getCopyToReg(Chain, dl, VA.getLocReg(),
OutVals[i], Flag);
// Guarantee that all emitted copies are stuck together,
// avoiding something bad.
Flag = Chain.getValue(1);
}
unsigned Opc = (CallConv == CallingConv::MSP430_INTR ?
MSP430ISD::RETI_FLAG : MSP430ISD::RET_FLAG);
if (Flag.getNode())
return DAG.getNode(Opc, dl, MVT::Other, Chain, Flag);
// Return Void
return DAG.getNode(Opc, 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 Chain, SDValue Callee,
CallingConv::ID CallConv, bool isVarArg,
bool isTailCall,
const SmallVectorImpl<ISD::OutputArg>
&Outs,
const SmallVectorImpl<SDValue> &OutVals,
const SmallVectorImpl<ISD::InputArg> &Ins,
DebugLoc dl, SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals) const {
// Analyze operands of the call, assigning locations to each operand.
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(),
getTargetMachine(), ArgLocs, *DAG.getContext());
CCInfo.AnalyzeCallOperands(Outs, 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];
SDValue Arg = OutVals[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,
MachinePointerInfo(),false, false, 0));
}
}
// 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 emitted 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(), dl, 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::Glue);
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 LowerCallResult(Chain, InFlag, CallConv, isVarArg, Ins, dl,
DAG, InVals);
}
/// LowerCallResult - Lower the result values of a call into the
/// appropriate copies out of appropriate physical registers.
///
SDValue
MSP430TargetLowering::LowerCallResult(SDValue Chain, SDValue InFlag,
CallingConv::ID CallConv, bool isVarArg,
const SmallVectorImpl<ISD::InputArg> &Ins,
DebugLoc dl, SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals) const {
// Assign locations to each value returned by this call.
SmallVector<CCValAssign, 16> RVLocs;
CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(),
getTargetMachine(), RVLocs, *DAG.getContext());
CCInfo.AnalyzeCallResult(Ins, RetCC_MSP430);
// 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);
InVals.push_back(Chain.getValue(0));
}
return Chain;
}
SDValue MSP430TargetLowering::LowerShifts(SDValue Op,
SelectionDAG &DAG) const {
unsigned Opc = Op.getOpcode();
SDNode* N = Op.getNode();
EVT VT = Op.getValueType();
DebugLoc dl = N->getDebugLoc();
// Expand non-constant shifts to loops:
if (!isa<ConstantSDNode>(N->getOperand(1)))
switch (Opc) {
default:
assert(0 && "Invalid shift opcode!");
case ISD::SHL:
return DAG.getNode(MSP430ISD::SHL, dl,
VT, N->getOperand(0), N->getOperand(1));
case ISD::SRA:
return DAG.getNode(MSP430ISD::SRA, dl,
VT, N->getOperand(0), N->getOperand(1));
case ISD::SRL:
return DAG.getNode(MSP430ISD::SRL, dl,
VT, N->getOperand(0), N->getOperand(1));
}
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 {
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, Op.getDebugLoc(),
getPointerTy(), Offset);
return DAG.getNode(MSP430ISD::Wrapper, Op.getDebugLoc(),
getPointerTy(), Result);
}
SDValue MSP430TargetLowering::LowerExternalSymbol(SDValue Op,
SelectionDAG &DAG) const {
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);;
}
SDValue MSP430TargetLowering::LowerBlockAddress(SDValue Op,
SelectionDAG &DAG) const {
DebugLoc dl = Op.getDebugLoc();
const BlockAddress *BA = cast<BlockAddressSDNode>(Op)->getBlockAddress();
SDValue Result = DAG.getBlockAddress(BA, getPointerTy(), /*isTarget=*/true);
return DAG.getNode(MSP430ISD::Wrapper, dl, getPointerTy(), Result);;
}
static SDValue EmitCMP(SDValue &LHS, SDValue &RHS, SDValue &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
MSP430CC::CondCodes TCC = MSP430CC::COND_INVALID;
switch (CC) {
default: llvm_unreachable("Invalid integer condition!");
case ISD::SETEQ:
TCC = MSP430CC::COND_E; // aka COND_Z
// Minor optimization: if LHS is a constant, swap operands, then the
// constant can be folded into comparison.
if (LHS.getOpcode() == ISD::Constant)
std::swap(LHS, RHS);
break;
case ISD::SETNE:
TCC = MSP430CC::COND_NE; // aka COND_NZ
// Minor optimization: if LHS is a constant, swap operands, then the
// constant can be folded into comparison.
if (LHS.getOpcode() == ISD::Constant)
std::swap(LHS, RHS);
break;
case ISD::SETULE:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETUGE:
// Turn lhs u>= rhs with lhs constant into rhs u< lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_LO;
break;
}
TCC = MSP430CC::COND_HS; // aka COND_C
break;
case ISD::SETUGT:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETULT:
// Turn lhs u< rhs with lhs constant into rhs u>= lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_HS;
break;
}
TCC = MSP430CC::COND_LO; // aka COND_NC
break;
case ISD::SETLE:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETGE:
// Turn lhs >= rhs with lhs constant into rhs < lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_L;
break;
}
TCC = MSP430CC::COND_GE;
break;
case ISD::SETGT:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETLT:
// Turn lhs < rhs with lhs constant into rhs >= lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_GE;
break;
}
TCC = MSP430CC::COND_L;
break;
}
TargetCC = DAG.getConstant(TCC, MVT::i8);
return DAG.getNode(MSP430ISD::CMP, dl, MVT::Glue, LHS, RHS);
}
SDValue MSP430TargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
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();
SDValue TargetCC;
SDValue Flag = EmitCMP(LHS, RHS, TargetCC, CC, dl, DAG);
return DAG.getNode(MSP430ISD::BR_CC, dl, Op.getValueType(),
Chain, Dest, TargetCC, Flag);
}
SDValue MSP430TargetLowering::LowerSETCC(SDValue Op, SelectionDAG &DAG) const {
SDValue LHS = Op.getOperand(0);
SDValue RHS = Op.getOperand(1);
DebugLoc dl = Op.getDebugLoc();
// If we are doing an AND and testing against zero, then the CMP
// will not be generated. The AND (or BIT) will generate the condition codes,
// but they are different from CMP.
// FIXME: since we're doing a post-processing, use a pseudoinstr here, so
// lowering & isel wouldn't diverge.
bool andCC = false;
if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(RHS)) {
if (RHSC->isNullValue() && LHS.hasOneUse() &&
(LHS.getOpcode() == ISD::AND ||
(LHS.getOpcode() == ISD::TRUNCATE &&
LHS.getOperand(0).getOpcode() == ISD::AND))) {
andCC = true;
}
}
ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(2))->get();
SDValue TargetCC;
SDValue Flag = EmitCMP(LHS, RHS, TargetCC, CC, dl, DAG);
// Get the condition codes directly from the status register, if its easy.
// Otherwise a branch will be generated. Note that the AND and BIT
// instructions generate different flags than CMP, the carry bit can be used
// for NE/EQ.
bool Invert = false;
bool Shift = false;
bool Convert = true;
switch (cast<ConstantSDNode>(TargetCC)->getZExtValue()) {
default:
Convert = false;
break;
case MSP430CC::COND_HS:
// Res = SRW & 1, no processing is required
break;
case MSP430CC::COND_LO:
// Res = ~(SRW & 1)
Invert = true;
break;
case MSP430CC::COND_NE:
if (andCC) {
// C = ~Z, thus Res = SRW & 1, no processing is required
} else {
// Res = ~((SRW >> 1) & 1)
Shift = true;
Invert = true;
}
break;
case MSP430CC::COND_E:
Shift = true;
// C = ~Z for AND instruction, thus we can put Res = ~(SRW & 1), however,
// Res = (SRW >> 1) & 1 is 1 word shorter.
break;
}
EVT VT = Op.getValueType();
SDValue One = DAG.getConstant(1, VT);
if (Convert) {
SDValue SR = DAG.getCopyFromReg(DAG.getEntryNode(), dl, MSP430::SRW,
MVT::i16, Flag);
if (Shift)
// FIXME: somewhere this is turned into a SRL, lower it MSP specific?
SR = DAG.getNode(ISD::SRA, dl, MVT::i16, SR, One);
SR = DAG.getNode(ISD::AND, dl, MVT::i16, SR, One);
if (Invert)
SR = DAG.getNode(ISD::XOR, dl, MVT::i16, SR, One);
return SR;
} else {
SDValue Zero = DAG.getConstant(0, VT);
SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Glue);
SmallVector<SDValue, 4> Ops;
Ops.push_back(One);
Ops.push_back(Zero);
Ops.push_back(TargetCC);
Ops.push_back(Flag);
return DAG.getNode(MSP430ISD::SELECT_CC, dl, VTs, &Ops[0], Ops.size());
}
}
SDValue MSP430TargetLowering::LowerSELECT_CC(SDValue Op,
SelectionDAG &DAG) const {
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();
SDValue TargetCC;
SDValue Flag = EmitCMP(LHS, RHS, TargetCC, CC, dl, DAG);
SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Glue);
SmallVector<SDValue, 4> Ops;
Ops.push_back(TrueV);
Ops.push_back(FalseV);
Ops.push_back(TargetCC);
Ops.push_back(Flag);
return DAG.getNode(MSP430ISD::SELECT_CC, dl, VTs, &Ops[0], Ops.size());
}
SDValue MSP430TargetLowering::LowerSIGN_EXTEND(SDValue Op,
SelectionDAG &DAG) const {
SDValue Val = Op.getOperand(0);
EVT 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()));
}
SDValue
MSP430TargetLowering::getReturnAddressFrameIndex(SelectionDAG &DAG) const {
MachineFunction &MF = DAG.getMachineFunction();
MSP430MachineFunctionInfo *FuncInfo = MF.getInfo<MSP430MachineFunctionInfo>();
int ReturnAddrIndex = FuncInfo->getRAIndex();
if (ReturnAddrIndex == 0) {
// Set up a frame object for the return address.
uint64_t SlotSize = TD->getPointerSize();
ReturnAddrIndex = MF.getFrameInfo()->CreateFixedObject(SlotSize, -SlotSize,
true);
FuncInfo->setRAIndex(ReturnAddrIndex);
}
return DAG.getFrameIndex(ReturnAddrIndex, getPointerTy());
}
SDValue MSP430TargetLowering::LowerRETURNADDR(SDValue Op,
SelectionDAG &DAG) const {
MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
MFI->setReturnAddressIsTaken(true);
unsigned Depth = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
DebugLoc dl = Op.getDebugLoc();
if (Depth > 0) {
SDValue FrameAddr = LowerFRAMEADDR(Op, DAG);
SDValue Offset =
DAG.getConstant(TD->getPointerSize(), MVT::i16);
return DAG.getLoad(getPointerTy(), dl, DAG.getEntryNode(),
DAG.getNode(ISD::ADD, dl, getPointerTy(),
FrameAddr, Offset),
MachinePointerInfo(), false, false, false, 0);
}
// Just load the return address.
SDValue RetAddrFI = getReturnAddressFrameIndex(DAG);
return DAG.getLoad(getPointerTy(), dl, DAG.getEntryNode(),
RetAddrFI, MachinePointerInfo(), false, false, false, 0);
}
SDValue MSP430TargetLowering::LowerFRAMEADDR(SDValue Op,
SelectionDAG &DAG) const {
MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
MFI->setFrameAddressIsTaken(true);
EVT VT = Op.getValueType();
DebugLoc dl = Op.getDebugLoc(); // FIXME probably not meaningful
unsigned Depth = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
SDValue FrameAddr = DAG.getCopyFromReg(DAG.getEntryNode(), dl,
MSP430::FPW, VT);
while (Depth--)
FrameAddr = DAG.getLoad(VT, dl, DAG.getEntryNode(), FrameAddr,
MachinePointerInfo(),
false, false, false, 0);
return FrameAddr;
}
/// getPostIndexedAddressParts - returns true by value, base pointer and
/// offset pointer and addressing mode by reference if this node can be
/// combined with a load / store to form a post-indexed load / store.
bool MSP430TargetLowering::getPostIndexedAddressParts(SDNode *N, SDNode *Op,
SDValue &Base,
SDValue &Offset,
ISD::MemIndexedMode &AM,
SelectionDAG &DAG) const {
LoadSDNode *LD = cast<LoadSDNode>(N);
if (LD->getExtensionType() != ISD::NON_EXTLOAD)
return false;
EVT VT = LD->getMemoryVT();
if (VT != MVT::i8 && VT != MVT::i16)
return false;
if (Op->getOpcode() != ISD::ADD)
return false;
if (ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(Op->getOperand(1))) {
uint64_t RHSC = RHS->getZExtValue();
if ((VT == MVT::i16 && RHSC != 2) ||
(VT == MVT::i8 && RHSC != 1))
return false;
Base = Op->getOperand(0);
Offset = DAG.getConstant(RHSC, VT);
AM = ISD::POST_INC;
return true;
}
return false;
}
const char *MSP430TargetLowering::getTargetNodeName(unsigned Opcode) const {
switch (Opcode) {
default: return NULL;
case MSP430ISD::RET_FLAG: return "MSP430ISD::RET_FLAG";
case MSP430ISD::RETI_FLAG: return "MSP430ISD::RETI_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";
case MSP430ISD::SHL: return "MSP430ISD::SHL";
case MSP430ISD::SRA: return "MSP430ISD::SRA";
}
}
bool MSP430TargetLowering::isTruncateFree(Type *Ty1,
Type *Ty2) const {
if (!Ty1->isIntegerTy() || !Ty2->isIntegerTy())
return false;
return (Ty1->getPrimitiveSizeInBits() > Ty2->getPrimitiveSizeInBits());
}
bool MSP430TargetLowering::isTruncateFree(EVT VT1, EVT VT2) const {
if (!VT1.isInteger() || !VT2.isInteger())
return false;
return (VT1.getSizeInBits() > VT2.getSizeInBits());
}
bool MSP430TargetLowering::isZExtFree(Type *Ty1, Type *Ty2) const {
// MSP430 implicitly zero-extends 8-bit results in 16-bit registers.
return 0 && Ty1->isIntegerTy(8) && Ty2->isIntegerTy(16);
}
bool MSP430TargetLowering::isZExtFree(EVT VT1, EVT VT2) const {
// MSP430 implicitly zero-extends 8-bit results in 16-bit registers.
return 0 && VT1 == MVT::i8 && VT2 == MVT::i16;
}
//===----------------------------------------------------------------------===//
// Other Lowering Code
//===----------------------------------------------------------------------===//
MachineBasicBlock*
MSP430TargetLowering::EmitShiftInstr(MachineInstr *MI,
MachineBasicBlock *BB) const {
MachineFunction *F = BB->getParent();
MachineRegisterInfo &RI = F->getRegInfo();
DebugLoc dl = MI->getDebugLoc();
const TargetInstrInfo &TII = *getTargetMachine().getInstrInfo();
unsigned Opc;
const TargetRegisterClass * RC;
switch (MI->getOpcode()) {
default:
assert(0 && "Invalid shift opcode!");
case MSP430::Shl8:
Opc = MSP430::SHL8r1;
RC = MSP430::GR8RegisterClass;
break;
case MSP430::Shl16:
Opc = MSP430::SHL16r1;
RC = MSP430::GR16RegisterClass;
break;
case MSP430::Sra8:
Opc = MSP430::SAR8r1;
RC = MSP430::GR8RegisterClass;
break;
case MSP430::Sra16:
Opc = MSP430::SAR16r1;
RC = MSP430::GR16RegisterClass;
break;
case MSP430::Srl8:
Opc = MSP430::SAR8r1c;
RC = MSP430::GR8RegisterClass;
break;
case MSP430::Srl16:
Opc = MSP430::SAR16r1c;
RC = MSP430::GR16RegisterClass;
break;
}
const BasicBlock *LLVM_BB = BB->getBasicBlock();
MachineFunction::iterator I = BB;
++I;
// Create loop block
MachineBasicBlock *LoopBB = F->CreateMachineBasicBlock(LLVM_BB);
MachineBasicBlock *RemBB = F->CreateMachineBasicBlock(LLVM_BB);
F->insert(I, LoopBB);
F->insert(I, RemBB);
// Update machine-CFG edges by transferring all successors of the current
// block to the block containing instructions after shift.
RemBB->splice(RemBB->begin(), BB,
llvm::next(MachineBasicBlock::iterator(MI)),
BB->end());
RemBB->transferSuccessorsAndUpdatePHIs(BB);
// Add adges BB => LoopBB => RemBB, BB => RemBB, LoopBB => LoopBB
BB->addSuccessor(LoopBB);
BB->addSuccessor(RemBB);
LoopBB->addSuccessor(RemBB);
LoopBB->addSuccessor(LoopBB);
unsigned ShiftAmtReg = RI.createVirtualRegister(MSP430::GR8RegisterClass);
unsigned ShiftAmtReg2 = RI.createVirtualRegister(MSP430::GR8RegisterClass);
unsigned ShiftReg = RI.createVirtualRegister(RC);
unsigned ShiftReg2 = RI.createVirtualRegister(RC);
unsigned ShiftAmtSrcReg = MI->getOperand(2).getReg();
unsigned SrcReg = MI->getOperand(1).getReg();
unsigned DstReg = MI->getOperand(0).getReg();
// BB:
// cmp 0, N
// je RemBB
BuildMI(BB, dl, TII.get(MSP430::CMP8ri))
.addReg(ShiftAmtSrcReg).addImm(0);
BuildMI(BB, dl, TII.get(MSP430::JCC))
.addMBB(RemBB)
.addImm(MSP430CC::COND_E);
// LoopBB:
// ShiftReg = phi [%SrcReg, BB], [%ShiftReg2, LoopBB]
// ShiftAmt = phi [%N, BB], [%ShiftAmt2, LoopBB]
// ShiftReg2 = shift ShiftReg
// ShiftAmt2 = ShiftAmt - 1;
BuildMI(LoopBB, dl, TII.get(MSP430::PHI), ShiftReg)
.addReg(SrcReg).addMBB(BB)
.addReg(ShiftReg2).addMBB(LoopBB);
BuildMI(LoopBB, dl, TII.get(MSP430::PHI), ShiftAmtReg)
.addReg(ShiftAmtSrcReg).addMBB(BB)
.addReg(ShiftAmtReg2).addMBB(LoopBB);
BuildMI(LoopBB, dl, TII.get(Opc), ShiftReg2)
.addReg(ShiftReg);
BuildMI(LoopBB, dl, TII.get(MSP430::SUB8ri), ShiftAmtReg2)
.addReg(ShiftAmtReg).addImm(1);
BuildMI(LoopBB, dl, TII.get(MSP430::JCC))
.addMBB(LoopBB)
.addImm(MSP430CC::COND_NE);
// RemBB:
// DestReg = phi [%SrcReg, BB], [%ShiftReg, LoopBB]
BuildMI(*RemBB, RemBB->begin(), dl, TII.get(MSP430::PHI), DstReg)
.addReg(SrcReg).addMBB(BB)
.addReg(ShiftReg2).addMBB(LoopBB);
MI->eraseFromParent(); // The pseudo instruction is gone now.
return RemBB;
}
MachineBasicBlock*
MSP430TargetLowering::EmitInstrWithCustomInserter(MachineInstr *MI,
MachineBasicBlock *BB) const {
unsigned Opc = MI->getOpcode();
if (Opc == MSP430::Shl8 || Opc == MSP430::Shl16 ||
Opc == MSP430::Sra8 || Opc == MSP430::Sra16 ||
Opc == MSP430::Srl8 || Opc == MSP430::Srl16)
return EmitShiftInstr(MI, BB);
const TargetInstrInfo &TII = *getTargetMachine().getInstrInfo();
DebugLoc dl = MI->getDebugLoc();
assert((Opc == MSP430::Select16 || Opc == 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);
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->splice(copy1MBB->begin(), BB,
llvm::next(MachineBasicBlock::iterator(MI)),
BB->end());
copy1MBB->transferSuccessorsAndUpdatePHIs(BB);
// Next, add the true and fallthrough blocks as its successors.
BB->addSuccessor(copy0MBB);
BB->addSuccessor(copy1MBB);
BuildMI(BB, dl, TII.get(MSP430::JCC))
.addMBB(copy1MBB)
.addImm(MI->getOperand(3).getImm());
// 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, BB->begin(), dl, TII.get(MSP430::PHI),
MI->getOperand(0).getReg())
.addReg(MI->getOperand(2).getReg()).addMBB(copy0MBB)
.addReg(MI->getOperand(1).getReg()).addMBB(thisMBB);
MI->eraseFromParent(); // The pseudo instruction is gone now.
return BB;
}
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