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260 lines
10 KiB
C++
260 lines
10 KiB
C++
//===-- InstrSelectionSupport.cpp -----------------------------------------===//
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//
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// Target-independent instruction selection code. See SparcInstrSelection.cpp
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// for usage.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/InstrSelectionSupport.h"
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#include "llvm/CodeGen/InstrSelection.h"
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#include "llvm/CodeGen/MachineInstrAnnot.h"
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#include "llvm/CodeGen/MachineCodeForInstruction.h"
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#include "llvm/CodeGen/InstrForest.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Constants.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/DerivedTypes.h"
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#include "../../Target/Sparc/SparcInstrSelectionSupport.h" // FIXME!
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// Generate code to load the constant into a TmpInstruction (virtual reg) and
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// returns the virtual register.
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//
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static TmpInstruction*
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InsertCodeToLoadConstant(Function *F,
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Value* opValue,
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Instruction* vmInstr,
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std::vector<MachineInstr*>& loadConstVec,
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TargetMachine& target)
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{
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// Create a tmp virtual register to hold the constant.
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MachineCodeForInstruction &mcfi = MachineCodeForInstruction::get(vmInstr);
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TmpInstruction* tmpReg = new TmpInstruction(mcfi, opValue);
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target.getInstrInfo().CreateCodeToLoadConst(target, F, opValue, tmpReg,
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loadConstVec, mcfi);
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// Record the mapping from the tmp VM instruction to machine instruction.
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// Do this for all machine instructions that were not mapped to any
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// other temp values created by
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// tmpReg->addMachineInstruction(loadConstVec.back());
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return tmpReg;
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}
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MachineOperand::MachineOperandType
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ChooseRegOrImmed(int64_t intValue,
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bool isSigned,
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MachineOpCode opCode,
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const TargetMachine& target,
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bool canUseImmed,
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unsigned int& getMachineRegNum,
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int64_t& getImmedValue)
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{
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MachineOperand::MachineOperandType opType=MachineOperand::MO_VirtualRegister;
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getMachineRegNum = 0;
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getImmedValue = 0;
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if (canUseImmed &&
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target.getInstrInfo().constantFitsInImmedField(opCode, intValue))
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{
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opType = isSigned? MachineOperand::MO_SignExtendedImmed
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: MachineOperand::MO_UnextendedImmed;
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getImmedValue = intValue;
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}
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else if (intValue == 0 && target.getRegInfo().getZeroRegNum() >= 0)
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{
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opType = MachineOperand::MO_MachineRegister;
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getMachineRegNum = target.getRegInfo().getZeroRegNum();
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}
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return opType;
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}
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MachineOperand::MachineOperandType
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ChooseRegOrImmed(Value* val,
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MachineOpCode opCode,
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const TargetMachine& target,
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bool canUseImmed,
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unsigned int& getMachineRegNum,
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int64_t& getImmedValue)
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{
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getMachineRegNum = 0;
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getImmedValue = 0;
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// To use reg or immed, constant needs to be integer, bool, or a NULL pointer
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// TargetInstrInfo::ConvertConstantToIntType() does the right conversions:
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bool isValidConstant;
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uint64_t valueToUse =
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target.getInstrInfo().ConvertConstantToIntType(target, val, val->getType(),
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isValidConstant);
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if (! isValidConstant)
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return MachineOperand::MO_VirtualRegister;
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// Now check if the constant value fits in the IMMED field.
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//
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return ChooseRegOrImmed((int64_t) valueToUse, val->getType()->isSigned(),
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opCode, target, canUseImmed,
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getMachineRegNum, getImmedValue);
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}
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//---------------------------------------------------------------------------
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// Function: FixConstantOperandsForInstr
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//
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// Purpose:
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// Special handling for constant operands of a machine instruction
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// -- if the constant is 0, use the hardwired 0 register, if any;
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// -- if the constant fits in the IMMEDIATE field, use that field;
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// -- else create instructions to put the constant into a register, either
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// directly or by loading explicitly from the constant pool.
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//
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// In the first 2 cases, the operand of `minstr' is modified in place.
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// Returns a vector of machine instructions generated for operands that
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// fall under case 3; these must be inserted before `minstr'.
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//---------------------------------------------------------------------------
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std::vector<MachineInstr*>
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FixConstantOperandsForInstr(Instruction* vmInstr,
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MachineInstr* minstr,
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TargetMachine& target)
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{
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std::vector<MachineInstr*> MVec;
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MachineOpCode opCode = minstr->getOpCode();
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const TargetInstrInfo& instrInfo = target.getInstrInfo();
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int resultPos = instrInfo.getResultPos(opCode);
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int immedPos = instrInfo.getImmedConstantPos(opCode);
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Function *F = vmInstr->getParent()->getParent();
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for (unsigned op=0; op < minstr->getNumOperands(); op++)
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{
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const MachineOperand& mop = minstr->getOperand(op);
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// Skip the result position, preallocated machine registers, or operands
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// that cannot be constants (CC regs or PC-relative displacements)
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if (resultPos == (int)op ||
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mop.getType() == MachineOperand::MO_MachineRegister ||
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mop.getType() == MachineOperand::MO_CCRegister ||
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mop.getType() == MachineOperand::MO_PCRelativeDisp)
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continue;
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bool constantThatMustBeLoaded = false;
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unsigned int machineRegNum = 0;
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int64_t immedValue = 0;
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Value* opValue = NULL;
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MachineOperand::MachineOperandType opType =
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MachineOperand::MO_VirtualRegister;
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// Operand may be a virtual register or a compile-time constant
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if (mop.getType() == MachineOperand::MO_VirtualRegister)
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{
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assert(mop.getVRegValue() != NULL);
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opValue = mop.getVRegValue();
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if (Constant *opConst = dyn_cast<Constant>(opValue)) {
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opType = ChooseRegOrImmed(opConst, opCode, target,
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(immedPos == (int)op), machineRegNum,
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immedValue);
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if (opType == MachineOperand::MO_VirtualRegister)
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constantThatMustBeLoaded = true;
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}
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}
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else
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{
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assert(mop.isImmediate());
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bool isSigned = mop.getType() == MachineOperand::MO_SignExtendedImmed;
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// Bit-selection flags indicate an instruction that is extracting
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// bits from its operand so ignore this even if it is a big constant.
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if (mop.opHiBits32() || mop.opLoBits32() ||
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mop.opHiBits64() || mop.opLoBits64())
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continue;
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opType = ChooseRegOrImmed(mop.getImmedValue(), isSigned,
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opCode, target, (immedPos == (int)op),
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machineRegNum, immedValue);
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if (opType == MachineOperand::MO_SignExtendedImmed ||
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opType == MachineOperand::MO_UnextendedImmed) {
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// The optype is an immediate value
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// This means we need to change the opcode, e.g. ADDr -> ADDi
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unsigned newOpcode = convertOpcodeFromRegToImm(opCode);
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minstr->setOpcode(newOpcode);
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}
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if (opType == mop.getType())
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continue; // no change: this is the most common case
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if (opType == MachineOperand::MO_VirtualRegister)
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{
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constantThatMustBeLoaded = true;
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opValue = isSigned
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? (Value*)ConstantSInt::get(Type::LongTy, immedValue)
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: (Value*)ConstantUInt::get(Type::ULongTy,(uint64_t)immedValue);
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}
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}
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if (opType == MachineOperand::MO_MachineRegister)
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minstr->SetMachineOperandReg(op, machineRegNum);
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else if (opType == MachineOperand::MO_SignExtendedImmed ||
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opType == MachineOperand::MO_UnextendedImmed) {
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minstr->SetMachineOperandConst(op, opType, immedValue);
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// The optype is or has become an immediate
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// This means we need to change the opcode, e.g. ADDr -> ADDi
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unsigned newOpcode = convertOpcodeFromRegToImm(opCode);
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minstr->setOpcode(newOpcode);
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} else if (constantThatMustBeLoaded ||
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(opValue && isa<GlobalValue>(opValue)))
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{ // opValue is a constant that must be explicitly loaded into a reg
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assert(opValue);
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TmpInstruction* tmpReg = InsertCodeToLoadConstant(F, opValue, vmInstr,
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MVec, target);
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minstr->SetMachineOperandVal(op, MachineOperand::MO_VirtualRegister,
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tmpReg);
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}
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}
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// Also, check for implicit operands used by the machine instruction
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// (no need to check those defined since they cannot be constants).
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// These include:
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// -- arguments to a Call
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// -- return value of a Return
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// Any such operand that is a constant value needs to be fixed also.
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// The current instructions with implicit refs (viz., Call and Return)
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// have no immediate fields, so the constant always needs to be loaded
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// into a register.
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//
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bool isCall = instrInfo.isCall(opCode);
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unsigned lastCallArgNum = 0; // unused if not a call
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CallArgsDescriptor* argDesc = NULL; // unused if not a call
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if (isCall)
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argDesc = CallArgsDescriptor::get(minstr);
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for (unsigned i=0, N=minstr->getNumImplicitRefs(); i < N; ++i)
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if (isa<Constant>(minstr->getImplicitRef(i)) ||
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isa<GlobalValue>(minstr->getImplicitRef(i)))
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{
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Value* oldVal = minstr->getImplicitRef(i);
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TmpInstruction* tmpReg =
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InsertCodeToLoadConstant(F, oldVal, vmInstr, MVec, target);
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minstr->setImplicitRef(i, tmpReg);
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if (isCall)
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{ // find and replace the argument in the CallArgsDescriptor
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unsigned i=lastCallArgNum;
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while (argDesc->getArgInfo(i).getArgVal() != oldVal)
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++i;
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assert(i < argDesc->getNumArgs() &&
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"Constant operands to a call *must* be in the arg list");
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lastCallArgNum = i;
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argDesc->getArgInfo(i).replaceArgVal(tmpReg);
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}
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}
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return MVec;
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}
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