1 //===- PHITransAddr.cpp - PHI Translation for Addresses -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the PHITransAddr class.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Analysis/PHITransAddr.h"
15 #include "llvm/Analysis/Dominators.h"
16 #include "llvm/Analysis/InstructionSimplify.h"
17 #include "llvm/Support/Debug.h"
18 #include "llvm/Support/raw_ostream.h"
21 static bool CanPHITrans(Instruction *Inst) {
22 if (isa<PHINode>(Inst) ||
23 isa<BitCastInst>(Inst) ||
24 isa<GetElementPtrInst>(Inst))
27 if (Inst->getOpcode() == Instruction::Add &&
28 isa<ConstantInt>(Inst->getOperand(1)))
31 // cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
32 // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
33 // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
37 void PHITransAddr::dump() const {
39 dbgs() << "PHITransAddr: null\n";
42 dbgs() << "PHITransAddr: " << *Addr << "\n";
43 for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
44 dbgs() << " Input #" << i << " is " << *InstInputs[i] << "\n";
48 static bool VerifySubExpr(Value *Expr,
49 SmallVectorImpl<Instruction*> &InstInputs) {
50 // If this is a non-instruction value, there is nothing to do.
51 Instruction *I = dyn_cast<Instruction>(Expr);
52 if (I == 0) return true;
54 // If it's an instruction, it is either in Tmp or its operands recursively
56 SmallVectorImpl<Instruction*>::iterator Entry =
57 std::find(InstInputs.begin(), InstInputs.end(), I);
58 if (Entry != InstInputs.end()) {
59 InstInputs.erase(Entry);
63 // If it isn't in the InstInputs list it is a subexpr incorporated into the
64 // address. Sanity check that it is phi translatable.
65 if (!CanPHITrans(I)) {
66 errs() << "Non phi translatable instruction found in PHITransAddr, either "
67 "something is missing from InstInputs or CanPHITrans is wrong:\n";
72 // Validate the operands of the instruction.
73 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
74 if (!VerifySubExpr(I->getOperand(i), InstInputs))
80 /// Verify - Check internal consistency of this data structure. If the
81 /// structure is valid, it returns true. If invalid, it prints errors and
83 bool PHITransAddr::Verify() const {
84 if (Addr == 0) return true;
86 SmallVector<Instruction*, 8> Tmp(InstInputs.begin(), InstInputs.end());
88 if (!VerifySubExpr(Addr, Tmp))
92 errs() << "PHITransAddr inconsistent, contains extra instructions:\n";
93 for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
94 errs() << " InstInput #" << i << " is " << *InstInputs[i] << "\n";
103 /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
104 /// if we have some hope of doing it. This should be used as a filter to
105 /// avoid calling PHITranslateValue in hopeless situations.
106 bool PHITransAddr::IsPotentiallyPHITranslatable() const {
107 // If the input value is not an instruction, or if it is not defined in CurBB,
108 // then we don't need to phi translate it.
109 Instruction *Inst = dyn_cast<Instruction>(Addr);
110 return Inst == 0 || CanPHITrans(Inst);
114 static void RemoveInstInputs(Value *V,
115 SmallVectorImpl<Instruction*> &InstInputs) {
116 Instruction *I = dyn_cast<Instruction>(V);
119 // If the instruction is in the InstInputs list, remove it.
120 SmallVectorImpl<Instruction*>::iterator Entry =
121 std::find(InstInputs.begin(), InstInputs.end(), I);
122 if (Entry != InstInputs.end()) {
123 InstInputs.erase(Entry);
127 assert(!isa<PHINode>(I) && "Error, removing something that isn't an input");
129 // Otherwise, it must have instruction inputs itself. Zap them recursively.
130 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
131 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
132 RemoveInstInputs(Op, InstInputs);
136 Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
137 BasicBlock *PredBB) {
138 // If this is a non-instruction value, it can't require PHI translation.
139 Instruction *Inst = dyn_cast<Instruction>(V);
140 if (Inst == 0) return V;
142 // Determine whether 'Inst' is an input to our PHI translatable expression.
143 bool isInput = std::count(InstInputs.begin(), InstInputs.end(), Inst);
145 // Handle inputs instructions if needed.
147 if (Inst->getParent() != CurBB) {
148 // If it is an input defined in a different block, then it remains an
153 // If 'Inst' is defined in this block and is an input that needs to be phi
154 // translated, we need to incorporate the value into the expression or fail.
156 // In either case, the instruction itself isn't an input any longer.
157 InstInputs.erase(std::find(InstInputs.begin(), InstInputs.end(), Inst));
159 // If this is a PHI, go ahead and translate it.
160 if (PHINode *PN = dyn_cast<PHINode>(Inst))
161 return AddAsInput(PN->getIncomingValueForBlock(PredBB));
163 // If this is a non-phi value, and it is analyzable, we can incorporate it
164 // into the expression by making all instruction operands be inputs.
165 if (!CanPHITrans(Inst))
168 // All instruction operands are now inputs (and of course, they may also be
169 // defined in this block, so they may need to be phi translated themselves.
170 for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
171 if (Instruction *Op = dyn_cast<Instruction>(Inst->getOperand(i)))
172 InstInputs.push_back(Op);
175 // Ok, it must be an intermediate result (either because it started that way
176 // or because we just incorporated it into the expression). See if its
177 // operands need to be phi translated, and if so, reconstruct it.
179 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
180 Value *PHIIn = PHITranslateSubExpr(BC->getOperand(0), CurBB, PredBB);
181 if (PHIIn == 0) return 0;
182 if (PHIIn == BC->getOperand(0))
185 // Find an available version of this cast.
187 // Constants are trivial to find.
188 if (Constant *C = dyn_cast<Constant>(PHIIn))
189 return AddAsInput(ConstantExpr::getBitCast(C, BC->getType()));
191 // Otherwise we have to see if a bitcasted version of the incoming pointer
192 // is available. If so, we can use it, otherwise we have to fail.
193 for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end();
195 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI))
196 if (BCI->getType() == BC->getType())
202 // Handle getelementptr with at least one PHI translatable operand.
203 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
204 SmallVector<Value*, 8> GEPOps;
205 bool AnyChanged = false;
206 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
207 Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB);
208 if (GEPOp == 0) return 0;
210 AnyChanged |= GEPOp != GEP->getOperand(i);
211 GEPOps.push_back(GEPOp);
217 // Simplify the GEP to handle 'gep x, 0' -> x etc.
218 if (Value *V = SimplifyGEPInst(&GEPOps[0], GEPOps.size(), TD)) {
219 for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
220 RemoveInstInputs(GEPOps[i], InstInputs);
222 return AddAsInput(V);
225 // Scan to see if we have this GEP available.
226 Value *APHIOp = GEPOps[0];
227 for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end();
229 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI))
230 if (GEPI->getType() == GEP->getType() &&
231 GEPI->getNumOperands() == GEPOps.size() &&
232 GEPI->getParent()->getParent() == CurBB->getParent()) {
233 bool Mismatch = false;
234 for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
235 if (GEPI->getOperand(i) != GEPOps[i]) {
246 // Handle add with a constant RHS.
247 if (Inst->getOpcode() == Instruction::Add &&
248 isa<ConstantInt>(Inst->getOperand(1))) {
249 // PHI translate the LHS.
250 Constant *RHS = cast<ConstantInt>(Inst->getOperand(1));
251 bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap();
252 bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap();
254 Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB);
255 if (LHS == 0) return 0;
257 // If the PHI translated LHS is an add of a constant, fold the immediates.
258 if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS))
259 if (BOp->getOpcode() == Instruction::Add)
260 if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
261 LHS = BOp->getOperand(0);
262 RHS = ConstantExpr::getAdd(RHS, CI);
263 isNSW = isNUW = false;
265 // If the old 'LHS' was an input, add the new 'LHS' as an input.
266 if (std::count(InstInputs.begin(), InstInputs.end(), BOp)) {
267 RemoveInstInputs(BOp, InstInputs);
272 // See if the add simplifies away.
273 if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, TD)) {
274 // If we simplified the operands, the LHS is no longer an input, but Res
276 RemoveInstInputs(LHS, InstInputs);
277 return AddAsInput(Res);
280 // If we didn't modify the add, just return it.
281 if (LHS == Inst->getOperand(0) && RHS == Inst->getOperand(1))
284 // Otherwise, see if we have this add available somewhere.
285 for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end();
287 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*UI))
288 if (BO->getOpcode() == Instruction::Add &&
289 BO->getOperand(0) == LHS && BO->getOperand(1) == RHS &&
290 BO->getParent()->getParent() == CurBB->getParent())
297 // Otherwise, we failed.
302 /// PHITranslateValue - PHI translate the current address up the CFG from
303 /// CurBB to Pred, updating our state the reflect any needed changes. This
304 /// returns true on failure and sets Addr to null.
305 bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB) {
306 assert(Verify() && "Invalid PHITransAddr!");
307 Addr = PHITranslateSubExpr(Addr, CurBB, PredBB);
308 assert(Verify() && "Invalid PHITransAddr!");
312 /// GetAvailablePHITranslatedSubExpr - Return the value computed by
313 /// PHITranslateSubExpr if it dominates PredBB, otherwise return null.
314 Value *PHITransAddr::
315 GetAvailablePHITranslatedSubExpr(Value *V, BasicBlock *CurBB,BasicBlock *PredBB,
316 const DominatorTree &DT) const {
317 PHITransAddr Tmp(V, TD);
318 Tmp.PHITranslateValue(CurBB, PredBB);
320 // See if PHI translation succeeds.
323 // Make sure the value is live in the predecessor.
324 if (Instruction *Inst = dyn_cast_or_null<Instruction>(V))
325 if (!DT.dominates(Inst->getParent(), PredBB))
331 /// PHITranslateWithInsertion - PHI translate this value into the specified
332 /// predecessor block, inserting a computation of the value if it is
335 /// All newly created instructions are added to the NewInsts list. This
336 /// returns null on failure.
338 Value *PHITransAddr::
339 PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
340 const DominatorTree &DT,
341 SmallVectorImpl<Instruction*> &NewInsts) {
342 unsigned NISize = NewInsts.size();
344 // Attempt to PHI translate with insertion.
345 Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts);
347 // If successful, return the new value.
348 if (Addr) return Addr;
350 // If not, destroy any intermediate instructions inserted.
351 while (NewInsts.size() != NISize)
352 NewInsts.pop_back_val()->eraseFromParent();
357 /// InsertPHITranslatedPointer - Insert a computation of the PHI translated
358 /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
359 /// block. All newly created instructions are added to the NewInsts list.
360 /// This returns null on failure.
362 Value *PHITransAddr::
363 InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
364 BasicBlock *PredBB, const DominatorTree &DT,
365 SmallVectorImpl<Instruction*> &NewInsts) {
366 // See if we have a version of this value already available and dominating
367 // PredBB. If so, there is no need to insert a new instance of it.
368 if (Value *Res = GetAvailablePHITranslatedSubExpr(InVal, CurBB, PredBB, DT))
371 // If we don't have an available version of this value, it must be an
373 Instruction *Inst = cast<Instruction>(InVal);
375 // Handle bitcast of PHI translatable value.
376 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
377 Value *OpVal = InsertPHITranslatedSubExpr(BC->getOperand(0),
378 CurBB, PredBB, DT, NewInsts);
379 if (OpVal == 0) return 0;
381 // Otherwise insert a bitcast at the end of PredBB.
382 BitCastInst *New = new BitCastInst(OpVal, InVal->getType(),
383 InVal->getName()+".phi.trans.insert",
384 PredBB->getTerminator());
385 NewInsts.push_back(New);
389 // Handle getelementptr with at least one PHI operand.
390 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
391 SmallVector<Value*, 8> GEPOps;
392 BasicBlock *CurBB = GEP->getParent();
393 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
394 Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i),
395 CurBB, PredBB, DT, NewInsts);
396 if (OpVal == 0) return 0;
397 GEPOps.push_back(OpVal);
400 GetElementPtrInst *Result =
401 GetElementPtrInst::Create(GEPOps[0], GEPOps.begin()+1, GEPOps.end(),
402 InVal->getName()+".phi.trans.insert",
403 PredBB->getTerminator());
404 Result->setIsInBounds(GEP->isInBounds());
405 NewInsts.push_back(Result);
410 // FIXME: This code works, but it is unclear that we actually want to insert
411 // a big chain of computation in order to make a value available in a block.
412 // This needs to be evaluated carefully to consider its cost trade offs.
414 // Handle add with a constant RHS.
415 if (Inst->getOpcode() == Instruction::Add &&
416 isa<ConstantInt>(Inst->getOperand(1))) {
417 // PHI translate the LHS.
418 Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0),
419 CurBB, PredBB, DT, NewInsts);
420 if (OpVal == 0) return 0;
422 BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1),
423 InVal->getName()+".phi.trans.insert",
424 PredBB->getTerminator());
425 Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap());
426 Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap());
427 NewInsts.push_back(Res);