1 //===-- InstrSelectionSupport.cpp -----------------------------------------===//
3 // Target-independent instruction selection code. See SparcInstrSelection.cpp
6 //===----------------------------------------------------------------------===//
8 #include "llvm/CodeGen/InstrSelectionSupport.h"
9 #include "llvm/CodeGen/InstrSelection.h"
10 #include "llvm/CodeGen/MachineInstr.h"
11 #include "llvm/CodeGen/MachineInstrAnnot.h"
12 #include "llvm/CodeGen/MachineCodeForInstruction.h"
13 #include "llvm/CodeGen/MachineCodeForMethod.h"
14 #include "llvm/CodeGen/InstrForest.h"
15 #include "llvm/Target/TargetMachine.h"
16 #include "llvm/Target/MachineRegInfo.h"
17 #include "llvm/Constants.h"
18 #include "llvm/Function.h"
19 #include "llvm/Type.h"
20 #include "llvm/iMemory.h"
23 //*************************** Local Functions ******************************/
26 // Generate code to load the constant into a TmpInstruction (virtual reg) and
27 // returns the virtual register.
29 static TmpInstruction*
30 InsertCodeToLoadConstant(Function *F,
33 vector<MachineInstr*>& loadConstVec,
34 TargetMachine& target)
36 // Create a tmp virtual register to hold the constant.
37 TmpInstruction* tmpReg = new TmpInstruction(opValue);
38 MachineCodeForInstruction &mcfi = MachineCodeForInstruction::get(vmInstr);
41 target.getInstrInfo().CreateCodeToLoadConst(target, F, opValue, tmpReg,
44 // Record the mapping from the tmp VM instruction to machine instruction.
45 // Do this for all machine instructions that were not mapped to any
46 // other temp values created by
47 // tmpReg->addMachineInstruction(loadConstVec.back());
53 //---------------------------------------------------------------------------
54 // Function GetConstantValueAsUnsignedInt
55 // Function GetConstantValueAsSignedInt
57 // Convenience functions to get the value of an integral constant, for an
58 // appropriate integer or non-integer type that can be held in a signed
59 // or unsigned integer respectively. The type of the argument must be
61 // Signed or unsigned integer
65 // isValidConstant is set to true if a valid constant was found.
66 //---------------------------------------------------------------------------
69 GetConstantValueAsUnsignedInt(const Value *V,
70 bool &isValidConstant)
72 isValidConstant = true;
75 if (const ConstantBool *CB = dyn_cast<ConstantBool>(V))
76 return (int64_t)CB->getValue();
77 else if (const ConstantSInt *CS = dyn_cast<ConstantSInt>(V))
78 return (uint64_t)CS->getValue();
79 else if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(V))
80 return CU->getValue();
82 isValidConstant = false;
87 GetConstantValueAsSignedInt(const Value *V,
88 bool &isValidConstant)
90 uint64_t C = GetConstantValueAsUnsignedInt(V, isValidConstant);
91 if (isValidConstant) {
92 if (V->getType()->isSigned() || C < INT64_MAX) // safe to cast to signed
95 isValidConstant = false;
101 //---------------------------------------------------------------------------
102 // Function: FoldGetElemChain
105 // Fold a chain of GetElementPtr instructions containing only
106 // constant offsets into an equivalent (Pointer, IndexVector) pair.
107 // Returns the pointer Value, and stores the resulting IndexVector
108 // in argument chainIdxVec. This is a helper function for
109 // FoldConstantIndices that does the actual folding.
110 //---------------------------------------------------------------------------
113 FoldGetElemChain(InstrTreeNode* ptrNode, vector<Value*>& chainIdxVec)
115 InstructionNode* gepNode = dyn_cast<InstructionNode>(ptrNode);
116 GetElementPtrInst* gepInst =
117 dyn_cast_or_null<GetElementPtrInst>(gepNode ? gepNode->getInstruction() :0);
119 // ptr value is not computed in this tree or ptr value does not come from GEP
124 // Return NULL if we don't fold any instructions in.
125 Value* ptrVal = NULL;
127 // Remember if the last instruction had a leading [0] index.
128 bool hasLeadingZero = false;
130 // Now chase the chain of getElementInstr instructions, if any.
131 // Check for any non-constant indices and stop there.
133 InstructionNode* ptrChild = gepNode;
134 while (ptrChild && (ptrChild->getOpLabel() == Instruction::GetElementPtr ||
135 ptrChild->getOpLabel() == GetElemPtrIdx))
137 // Child is a GetElemPtr instruction
138 gepInst = cast<GetElementPtrInst>(ptrChild->getValue());
139 User::op_iterator OI, firstIdx = gepInst->idx_begin();
140 User::op_iterator lastIdx = gepInst->idx_end();
141 bool allConstantOffsets = true;
143 // Check that all offsets are constant for this instruction
144 for (OI = firstIdx; allConstantOffsets && OI != lastIdx; ++OI)
145 allConstantOffsets = isa<ConstantInt>(*OI);
147 if (allConstantOffsets)
148 { // Get pointer value out of ptrChild.
149 ptrVal = gepInst->getPointerOperand();
151 // Check for a leading [0] index, if any. It will be discarded later.
152 hasLeadingZero = (*firstIdx ==
153 Constant::getNullValue((*firstIdx)->getType()));
155 // Insert its index vector at the start, skipping any leading [0]
156 chainIdxVec.insert(chainIdxVec.begin(),
157 firstIdx + hasLeadingZero, lastIdx);
159 // Mark the folded node so no code is generated for it.
160 ((InstructionNode*) ptrChild)->markFoldedIntoParent();
162 else // cannot fold this getElementPtr instr. or any further ones
165 ptrChild = dyn_cast<InstructionNode>(ptrChild->leftChild());
168 // If the first getElementPtr instruction had a leading [0], add it back.
169 // Note that this instruction is the *last* one successfully folded above.
170 if (ptrVal && hasLeadingZero)
171 chainIdxVec.insert(chainIdxVec.begin(), ConstantSInt::get(Type::LongTy,0));
177 //---------------------------------------------------------------------------
178 // Function: GetMemInstArgs
181 // Get the pointer value and the index vector for a memory operation
182 // (GetElementPtr, Load, or Store). If all indices of the given memory
183 // operation are constant, fold in constant indices in a chain of
184 // preceding GetElementPtr instructions (if any), and return the
185 // pointer value of the first instruction in the chain.
186 // All folded instructions are marked so no code is generated for them.
189 // Returns the pointer Value to use.
190 // Returns the resulting IndexVector in idxVec.
191 // Returns true/false in allConstantIndices if all indices are/aren't const.
192 //---------------------------------------------------------------------------
195 // Check for a constant (uint) 0.
199 return (isa<ConstantInt>(idx) && cast<ConstantInt>(idx)->isNullValue());
203 GetMemInstArgs(const InstructionNode* memInstrNode,
204 vector<Value*>& idxVec,
205 bool& allConstantIndices)
207 allConstantIndices = true;
208 Instruction* memInst = memInstrNode->getInstruction();
210 // If there is a GetElemPtr instruction to fold in to this instr,
211 // it must be in the left child for Load and GetElemPtr, and in the
212 // right child for Store instructions.
213 InstrTreeNode* ptrChild = (memInst->getOpcode() == Instruction::Store
214 ? memInstrNode->rightChild()
215 : memInstrNode->leftChild());
217 // Default pointer is the one from the current instruction.
218 Value* ptrVal = ptrChild->getValue();
220 // GEP is the only indexed memory instruction. gepI is used below.
221 GetElementPtrInst* gepI = dyn_cast<GetElementPtrInst>(memInst);
223 // If memInst is a GEP, check if all indices are constant for this instruction
225 for (User::op_iterator OI=gepI->idx_begin(), OE=gepI->idx_end();
226 allConstantIndices && OI != OE; ++OI)
227 if (! isa<Constant>(*OI))
228 allConstantIndices = false; // note: this also terminates loop!
230 // If we have only constant indices, fold chains of constant indices
231 // in this and any preceding GetElemPtr instructions.
232 bool foldedGEPs = false;
233 if (allConstantIndices)
234 if (Value* newPtr = FoldGetElemChain(ptrChild, idxVec))
238 assert((!gepI || IsZero(*gepI->idx_begin())) && "1st index not 0");
241 // Append the index vector of the current instruction, if any.
242 // Skip the leading [0] index if preceding GEPs were folded into this.
244 idxVec.insert(idxVec.end(), gepI->idx_begin() +foldedGEPs, gepI->idx_end());
249 //------------------------------------------------------------------------
250 // Function Set2OperandsFromInstr
251 // Function Set3OperandsFromInstr
253 // For the common case of 2- and 3-operand arithmetic/logical instructions,
254 // set the m/c instr. operands directly from the VM instruction's operands.
255 // Check whether the first or second operand is 0 and can use a dedicated "0"
257 // Check whether the second operand should use an immediate field or register.
258 // (First and third operands are never immediates for such instructions.)
261 // canDiscardResult: Specifies that the result operand can be discarded
262 // by using the dedicated "0"
264 // op1position, op2position and resultPosition: Specify in which position
265 // in the machine instruction the 3 operands (arg1, arg2
266 // and result) should go.
268 //------------------------------------------------------------------------
271 Set2OperandsFromInstr(MachineInstr* minstr,
272 InstructionNode* vmInstrNode,
273 const TargetMachine& target,
274 bool canDiscardResult,
278 Set3OperandsFromInstr(minstr, vmInstrNode, target,
279 canDiscardResult, op1Position,
280 /*op2Position*/ -1, resultPosition);
285 Set3OperandsFromInstr(MachineInstr* minstr,
286 InstructionNode* vmInstrNode,
287 const TargetMachine& target,
288 bool canDiscardResult,
293 assert(op1Position >= 0);
294 assert(resultPosition >= 0);
297 minstr->SetMachineOperandVal(op1Position, MachineOperand::MO_VirtualRegister,
298 vmInstrNode->leftChild()->getValue());
300 // operand 2 (if any)
301 if (op2Position >= 0)
302 minstr->SetMachineOperandVal(op2Position, MachineOperand::MO_VirtualRegister,
303 vmInstrNode->rightChild()->getValue());
305 // result operand: if it can be discarded, use a dead register if one exists
306 if (canDiscardResult && target.getRegInfo().getZeroRegNum() >= 0)
307 minstr->SetMachineOperandReg(resultPosition,
308 target.getRegInfo().getZeroRegNum());
310 minstr->SetMachineOperandVal(resultPosition,
311 MachineOperand::MO_VirtualRegister, vmInstrNode->getValue());
315 MachineOperand::MachineOperandType
316 ChooseRegOrImmed(int64_t intValue,
318 MachineOpCode opCode,
319 const TargetMachine& target,
321 unsigned int& getMachineRegNum,
322 int64_t& getImmedValue)
324 MachineOperand::MachineOperandType opType=MachineOperand::MO_VirtualRegister;
325 getMachineRegNum = 0;
329 target.getInstrInfo().constantFitsInImmedField(opCode, intValue))
331 opType = isSigned? MachineOperand::MO_SignExtendedImmed
332 : MachineOperand::MO_UnextendedImmed;
333 getImmedValue = intValue;
335 else if (intValue == 0 && target.getRegInfo().getZeroRegNum() >= 0)
337 opType = MachineOperand::MO_MachineRegister;
338 getMachineRegNum = target.getRegInfo().getZeroRegNum();
345 MachineOperand::MachineOperandType
346 ChooseRegOrImmed(Value* val,
347 MachineOpCode opCode,
348 const TargetMachine& target,
350 unsigned int& getMachineRegNum,
351 int64_t& getImmedValue)
353 getMachineRegNum = 0;
356 // To use reg or immed, constant needs to be integer, bool, or a NULL pointer
357 Constant *CPV = dyn_cast<Constant>(val);
359 (! CPV->getType()->isIntegral() &&
360 ! (isa<PointerType>(CPV->getType()) && CPV->isNullValue())))
361 return MachineOperand::MO_VirtualRegister;
363 // Now get the constant value and check if it fits in the IMMED field.
364 // Take advantage of the fact that the max unsigned value will rarely
365 // fit into any IMMED field and ignore that case (i.e., cast smaller
366 // unsigned constants to signed).
369 if (isa<PointerType>(CPV->getType()))
370 intValue = 0; // We checked above that it is NULL
371 else if (ConstantBool* CB = dyn_cast<ConstantBool>(CPV))
372 intValue = (int64_t) CB->getValue();
373 else if (CPV->getType()->isSigned())
374 intValue = cast<ConstantSInt>(CPV)->getValue();
377 assert(CPV->getType()->isUnsigned() && "Not pointer, bool, or integer?");
378 uint64_t V = cast<ConstantUInt>(CPV)->getValue();
379 if (V >= INT64_MAX) return MachineOperand::MO_VirtualRegister;
380 intValue = (int64_t) V;
383 return ChooseRegOrImmed(intValue, CPV->getType()->isSigned(),
384 opCode, target, canUseImmed,
385 getMachineRegNum, getImmedValue);
389 //---------------------------------------------------------------------------
390 // Function: FixConstantOperandsForInstr
393 // Special handling for constant operands of a machine instruction
394 // -- if the constant is 0, use the hardwired 0 register, if any;
395 // -- if the constant fits in the IMMEDIATE field, use that field;
396 // -- else create instructions to put the constant into a register, either
397 // directly or by loading explicitly from the constant pool.
399 // In the first 2 cases, the operand of `minstr' is modified in place.
400 // Returns a vector of machine instructions generated for operands that
401 // fall under case 3; these must be inserted before `minstr'.
402 //---------------------------------------------------------------------------
404 vector<MachineInstr*>
405 FixConstantOperandsForInstr(Instruction* vmInstr,
406 MachineInstr* minstr,
407 TargetMachine& target)
409 vector<MachineInstr*> loadConstVec;
411 MachineOpCode opCode = minstr->getOpCode();
412 const MachineInstrInfo& instrInfo = target.getInstrInfo();
413 const MachineInstrDescriptor& instrDesc = instrInfo.getDescriptor(opCode);
414 int immedPos = instrInfo.getImmedConstantPos(opCode);
416 Function *F = vmInstr->getParent()->getParent();
418 for (unsigned op=0; op < minstr->getNumOperands(); op++)
420 const MachineOperand& mop = minstr->getOperand(op);
422 // Skip the result position, preallocated machine registers, or operands
423 // that cannot be constants (CC regs or PC-relative displacements)
424 if (instrDesc.resultPos == (int) op ||
425 mop.getOperandType() == MachineOperand::MO_MachineRegister ||
426 mop.getOperandType() == MachineOperand::MO_CCRegister ||
427 mop.getOperandType() == MachineOperand::MO_PCRelativeDisp)
430 bool constantThatMustBeLoaded = false;
431 unsigned int machineRegNum = 0;
432 int64_t immedValue = 0;
433 Value* opValue = NULL;
434 MachineOperand::MachineOperandType opType =
435 MachineOperand::MO_VirtualRegister;
437 // Operand may be a virtual register or a compile-time constant
438 if (mop.getOperandType() == MachineOperand::MO_VirtualRegister)
440 assert(mop.getVRegValue() != NULL);
441 opValue = mop.getVRegValue();
442 if (Constant *opConst = dyn_cast<Constant>(opValue))
444 opType = ChooseRegOrImmed(opConst, opCode, target,
445 (immedPos == (int)op), machineRegNum, immedValue);
446 if (opType == MachineOperand::MO_VirtualRegister)
447 constantThatMustBeLoaded = true;
452 assert(mop.getOperandType() == MachineOperand::MO_SignExtendedImmed ||
453 mop.getOperandType() == MachineOperand::MO_UnextendedImmed);
455 bool isSigned = (mop.getOperandType() ==
456 MachineOperand::MO_SignExtendedImmed);
458 // Bit-selection flags indicate an instruction that is extracting
459 // bits from its operand so ignore this even if it is a big constant.
460 if (mop.opHiBits32() || mop.opLoBits32() ||
461 mop.opHiBits64() || mop.opLoBits64())
464 opType = ChooseRegOrImmed(mop.getImmedValue(), isSigned,
465 opCode, target, (immedPos == (int)op),
466 machineRegNum, immedValue);
468 if (opType == mop.getOperandType())
469 continue; // no change: this is the most common case
471 if (opType == MachineOperand::MO_VirtualRegister)
473 constantThatMustBeLoaded = true;
475 ? ConstantSInt::get(Type::LongTy, immedValue)
476 : ConstantUInt::get(Type::ULongTy, (uint64_t) immedValue);
480 if (opType == MachineOperand::MO_MachineRegister)
481 minstr->SetMachineOperandReg(op, machineRegNum);
482 else if (opType == MachineOperand::MO_SignExtendedImmed ||
483 opType == MachineOperand::MO_UnextendedImmed)
484 minstr->SetMachineOperandConst(op, opType, immedValue);
485 else if (constantThatMustBeLoaded ||
486 (opValue && isa<GlobalValue>(opValue)))
487 { // opValue is a constant that must be explicitly loaded into a reg
489 TmpInstruction* tmpReg = InsertCodeToLoadConstant(F, opValue, vmInstr,
490 loadConstVec, target);
491 minstr->SetMachineOperandVal(op, MachineOperand::MO_VirtualRegister,
496 // Also, check for implicit operands used by the machine instruction
497 // (no need to check those defined since they cannot be constants).
499 // -- arguments to a Call
500 // -- return value of a Return
501 // Any such operand that is a constant value needs to be fixed also.
502 // The current instructions with implicit refs (viz., Call and Return)
503 // have no immediate fields, so the constant always needs to be loaded
506 bool isCall = instrInfo.isCall(opCode);
507 unsigned lastCallArgNum = 0; // unused if not a call
508 CallArgsDescriptor* argDesc = NULL; // unused if not a call
510 argDesc = CallArgsDescriptor::get(minstr);
512 for (unsigned i=0, N=minstr->getNumImplicitRefs(); i < N; ++i)
513 if (isa<Constant>(minstr->getImplicitRef(i)) ||
514 isa<GlobalValue>(minstr->getImplicitRef(i)))
516 Value* oldVal = minstr->getImplicitRef(i);
517 TmpInstruction* tmpReg =
518 InsertCodeToLoadConstant(F, oldVal, vmInstr, loadConstVec, target);
519 minstr->setImplicitRef(i, tmpReg);
522 { // find and replace the argument in the CallArgsDescriptor
523 unsigned i=lastCallArgNum;
524 while (argDesc->getArgInfo(i).getArgVal() != oldVal)
526 assert(i < argDesc->getNumArgs() &&
527 "Constant operands to a call *must* be in the arg list");
529 argDesc->getArgInfo(i).replaceArgVal(tmpReg);