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);
117 return NULL; // ptr value is not computed in this tree
119 GetElementPtrInst* gepInst =
120 dyn_cast<GetElementPtrInst>(gepNode->getInstruction());
121 if (gepInst == NULL) // ptr value does not come from GEP instruction
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 ConstantUInt* CV = dyn_cast<ConstantUInt>((Value*) *firstIdx);
153 hasLeadingZero = bool(CV && CV->getValue() == 0);
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(), ConstantUInt::get(Type::UIntTy,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(Value* val,
317 MachineOpCode opCode,
318 const TargetMachine& target,
320 unsigned int& getMachineRegNum,
321 int64_t& getImmedValue)
323 MachineOperand::MachineOperandType opType =
324 MachineOperand::MO_VirtualRegister;
325 getMachineRegNum = 0;
328 // Check for the common case first: argument is not constant
330 Constant *CPV = dyn_cast<Constant>(val);
331 if (!CPV) return opType;
333 if (ConstantBool *CPB = dyn_cast<ConstantBool>(CPV))
335 if (!CPB->getValue() && target.getRegInfo().getZeroRegNum() >= 0)
337 getMachineRegNum = target.getRegInfo().getZeroRegNum();
338 return MachineOperand::MO_MachineRegister;
342 return MachineOperand::MO_SignExtendedImmed;
345 // Otherwise it needs to be an integer or a NULL pointer
346 if (! CPV->getType()->isInteger() &&
347 ! (isa<PointerType>(CPV->getType()) &&
351 // Now get the constant value and check if it fits in the IMMED field.
352 // Take advantage of the fact that the max unsigned value will rarely
353 // fit into any IMMED field and ignore that case (i.e., cast smaller
354 // unsigned constants to signed).
357 if (isa<PointerType>(CPV->getType()))
361 else if (CPV->getType()->isSigned())
363 intValue = cast<ConstantSInt>(CPV)->getValue();
367 uint64_t V = cast<ConstantUInt>(CPV)->getValue();
368 if (V >= INT64_MAX) return opType;
369 intValue = (int64_t)V;
372 if (intValue == 0 && target.getRegInfo().getZeroRegNum() >= 0)
374 opType = MachineOperand::MO_MachineRegister;
375 getMachineRegNum = target.getRegInfo().getZeroRegNum();
377 else if (canUseImmed &&
378 target.getInstrInfo().constantFitsInImmedField(opCode, intValue))
380 opType = CPV->getType()->isSigned()
381 ? MachineOperand::MO_SignExtendedImmed
382 : MachineOperand::MO_UnextendedImmed;
383 getImmedValue = intValue;
390 //---------------------------------------------------------------------------
391 // Function: FixConstantOperandsForInstr
394 // Special handling for constant operands of a machine instruction
395 // -- if the constant is 0, use the hardwired 0 register, if any;
396 // -- if the constant fits in the IMMEDIATE field, use that field;
397 // -- else create instructions to put the constant into a register, either
398 // directly or by loading explicitly from the constant pool.
400 // In the first 2 cases, the operand of `minstr' is modified in place.
401 // Returns a vector of machine instructions generated for operands that
402 // fall under case 3; these must be inserted before `minstr'.
403 //---------------------------------------------------------------------------
405 vector<MachineInstr*>
406 FixConstantOperandsForInstr(Instruction* vmInstr,
407 MachineInstr* minstr,
408 TargetMachine& target)
410 vector<MachineInstr*> loadConstVec;
412 const MachineInstrDescriptor& instrDesc =
413 target.getInstrInfo().getDescriptor(minstr->getOpCode());
415 Function *F = vmInstr->getParent()->getParent();
417 for (unsigned op=0; op < minstr->getNumOperands(); op++)
419 const MachineOperand& mop = minstr->getOperand(op);
421 // skip the result position (for efficiency below) and any other
422 // positions already marked as not a virtual register
423 if (instrDesc.resultPos == (int) op ||
424 mop.getOperandType() != MachineOperand::MO_VirtualRegister ||
425 mop.getVRegValue() == NULL)
430 Value* opValue = mop.getVRegValue();
431 bool constantThatMustBeLoaded = false;
433 if (Constant *opConst = dyn_cast<Constant>(opValue))
435 unsigned int machineRegNum;
437 MachineOperand::MachineOperandType opType =
438 ChooseRegOrImmed(opValue, minstr->getOpCode(), target,
439 (target.getInstrInfo().getImmedConstantPos(minstr->getOpCode()) == (int) op),
440 machineRegNum, immedValue);
442 if (opType == MachineOperand::MO_MachineRegister)
443 minstr->SetMachineOperandReg(op, machineRegNum);
444 else if (opType == MachineOperand::MO_VirtualRegister)
445 constantThatMustBeLoaded = true; // load is generated below
447 minstr->SetMachineOperandConst(op, opType, immedValue);
450 if (constantThatMustBeLoaded || isa<GlobalValue>(opValue))
451 { // opValue is a constant that must be explicitly loaded into a reg.
452 TmpInstruction* tmpReg = InsertCodeToLoadConstant(F, opValue,vmInstr,
455 minstr->SetMachineOperandVal(op, MachineOperand::MO_VirtualRegister,
461 // Also, check for implicit operands used by the machine instruction
462 // (no need to check those defined since they cannot be constants).
464 // -- arguments to a Call
465 // -- return value of a Return
466 // Any such operand that is a constant value needs to be fixed also.
467 // The current instructions with implicit refs (viz., Call and Return)
468 // have no immediate fields, so the constant always needs to be loaded
471 bool isCall = target.getInstrInfo().isCall(minstr->getOpCode());
472 unsigned lastCallArgNum = 0; // unused if not a call
473 CallArgsDescriptor* argDesc = NULL; // unused if not a call
475 argDesc = CallArgsDescriptor::get(minstr);
477 for (unsigned i=0, N=minstr->getNumImplicitRefs(); i < N; ++i)
478 if (isa<Constant>(minstr->getImplicitRef(i)) ||
479 isa<GlobalValue>(minstr->getImplicitRef(i)))
481 Value* oldVal = minstr->getImplicitRef(i);
482 TmpInstruction* tmpReg =
483 InsertCodeToLoadConstant(F, oldVal, vmInstr, loadConstVec, target);
484 minstr->setImplicitRef(i, tmpReg);
487 { // find and replace the argument in the CallArgsDescriptor
488 unsigned i=lastCallArgNum;
489 while (argDesc->getArgInfo(i).getArgVal() != oldVal)
491 assert(i < argDesc->getNumArgs() &&
492 "Constant operands to a call *must* be in the arg list");
494 argDesc->getArgInfo(i).replaceArgVal(tmpReg);