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Chris Lattner210e45a2009-12-04 02:10:16 +00001//===- PHITransAddr.cpp - PHI Translation for Addresses -------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the PHITransAddr class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Analysis/PHITransAddr.h"
15#include "llvm/Analysis/Dominators.h"
Chris Lattner9a864122009-12-07 18:36:53 +000016#include "llvm/Analysis/InstructionSimplify.h"
Chris Lattner210e45a2009-12-04 02:10:16 +000017using namespace llvm;
18
Chris Lattner6fcca1c2009-12-07 19:04:49 +000019static bool CanPHITrans(Instruction *Inst) {
20 if (isa<PHINode>(Inst) ||
21 isa<BitCastInst>(Inst) ||
22 isa<GetElementPtrInst>(Inst))
23 return true;
24
25 if (Inst->getOpcode() == Instruction::And &&
26 isa<ConstantInt>(Inst->getOperand(1)))
27 return true;
28
29 // cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
30 // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
31 // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
32 return false;
33}
34
Chris Lattner9a864122009-12-07 18:36:53 +000035/// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
36/// if we have some hope of doing it. This should be used as a filter to
37/// avoid calling PHITranslateValue in hopeless situations.
38bool PHITransAddr::IsPotentiallyPHITranslatable() const {
39 // If the input value is not an instruction, or if it is not defined in CurBB,
40 // then we don't need to phi translate it.
41 Instruction *Inst = dyn_cast<Instruction>(Addr);
Chris Lattner6fcca1c2009-12-07 19:04:49 +000042 return Inst == 0 || CanPHITrans(Inst);
Chris Lattner210e45a2009-12-04 02:10:16 +000043}
44
Chris Lattner9a864122009-12-07 18:36:53 +000045
46Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
47 BasicBlock *PredBB) {
48 // If this is a non-instruction value, it can't require PHI translation.
49 Instruction *Inst = dyn_cast<Instruction>(V);
50 if (Inst == 0) return V;
51
Chris Lattner6fcca1c2009-12-07 19:04:49 +000052 // If 'Inst' is defined in this block, it must be an input that needs to be
53 // phi translated or an intermediate expression that needs to be incorporated
54 // into the expression.
55 if (Inst->getParent() == CurBB) {
56 assert(std::count(InstInputs.begin(), InstInputs.end(), Inst) &&
57 "Not an input?");
58
59 // If this is a PHI, go ahead and translate it.
60 if (PHINode *PN = dyn_cast<PHINode>(Inst))
61 return PN->getIncomingValueForBlock(PredBB);
62
63
64 // If this is a non-phi value, and it is analyzable, we can incorporate it
65 // into the expression by making all instruction operands be inputs.
66 if (!CanPHITrans(Inst))
67 return 0;
68
69 // Okay, we can incorporate it, this instruction is no longer an input.
70 InstInputs.erase(std::find(InstInputs.begin(), InstInputs.end(), Inst));
71
72 // All instruction operands are now inputs (and of course, they may also be
73 // defined in this block, so they may need to be phi translated themselves.
74 for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
75 if (Instruction *Op = dyn_cast<Instruction>(Inst->getOperand(i)))
76 InstInputs.push_back(Op);
77
78 } else {
79 // Determine whether 'Inst' is an input to our PHI translatable expression.
80 bool isInput = std::count(InstInputs.begin(), InstInputs.end(), Inst);
81
82 // If it is an input defined in a different block, then it remains an input.
Chris Lattner9a864122009-12-07 18:36:53 +000083 if (isInput)
84 return Inst;
Chris Lattner9a864122009-12-07 18:36:53 +000085 }
86
Chris Lattner6fcca1c2009-12-07 19:04:49 +000087 // Ok, it must be an intermediate result (either because it started that way
88 // or because we just incorporated it into the expression). See if its
89 // operands need to be phi translated, and if so, reconstruct it.
Chris Lattner9a864122009-12-07 18:36:53 +000090
Chris Lattner6fcca1c2009-12-07 19:04:49 +000091 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
92 Value *PHIIn = PHITranslateSubExpr(BC->getOperand(0), CurBB, PredBB);
93 if (PHIIn == 0) return 0;
94 if (PHIIn == BC->getOperand(0))
95 return BC;
96
97 // Find an available version of this cast.
98
99 // Constants are trivial to find.
100 if (Constant *C = dyn_cast<Constant>(PHIIn))
101 return ConstantExpr::getBitCast(C, BC->getType());
102
103 // Otherwise we have to see if a bitcasted version of the incoming pointer
104 // is available. If so, we can use it, otherwise we have to fail.
105 for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end();
106 UI != E; ++UI) {
107 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI))
108 if (BCI->getType() == BC->getType())
109 return BCI;
110 }
111 return 0;
112 }
Chris Lattner9a864122009-12-07 18:36:53 +0000113
Chris Lattner6fcca1c2009-12-07 19:04:49 +0000114 // Handle getelementptr with at least one PHI translatable operand.
115 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
116 SmallVector<Value*, 8> GEPOps;
117 BasicBlock *CurBB = GEP->getParent();
118 bool AnyChanged = false;
119 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
120 Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB);
121 if (GEPOp == 0) return 0;
122
Chris Lattner60454172009-12-07 19:52:57 +0000123 AnyChanged |= GEPOp != GEP->getOperand(i);
Chris Lattner6fcca1c2009-12-07 19:04:49 +0000124 GEPOps.push_back(GEPOp);
125 }
126
127 if (!AnyChanged)
128 return GEP;
129
130 // Simplify the GEP to handle 'gep x, 0' -> x etc.
131 if (Value *V = SimplifyGEPInst(&GEPOps[0], GEPOps.size(), TD))
132 return V;
133
134 // Scan to see if we have this GEP available.
135 Value *APHIOp = GEPOps[0];
136 for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end();
137 UI != E; ++UI) {
138 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI))
139 if (GEPI->getType() == GEP->getType() &&
140 GEPI->getNumOperands() == GEPOps.size() &&
141 GEPI->getParent()->getParent() == CurBB->getParent()) {
142 bool Mismatch = false;
143 for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
144 if (GEPI->getOperand(i) != GEPOps[i]) {
145 Mismatch = true;
146 break;
147 }
148 if (!Mismatch)
149 return GEPI;
150 }
151 }
152 return 0;
153 }
154
155 // Handle add with a constant RHS.
156 if (Inst->getOpcode() == Instruction::Add &&
157 isa<ConstantInt>(Inst->getOperand(1))) {
158 // PHI translate the LHS.
159 Constant *RHS = cast<ConstantInt>(Inst->getOperand(1));
160 bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap();
161 bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap();
162
163 Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB);
164 if (LHS == 0) return 0;
165
166 // If the PHI translated LHS is an add of a constant, fold the immediates.
167 if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS))
168 if (BOp->getOpcode() == Instruction::Add)
169 if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
170 LHS = BOp->getOperand(0);
171 RHS = ConstantExpr::getAdd(RHS, CI);
172 isNSW = isNUW = false;
173 }
174
175 // See if the add simplifies away.
176 if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, TD))
177 return Res;
178
179 // Otherwise, see if we have this add available somewhere.
180 for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end();
181 UI != E; ++UI) {
182 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*UI))
183 if (BO->getOperand(0) == LHS && BO->getOperand(1) == RHS &&
184 BO->getParent()->getParent() == CurBB->getParent())
185 return BO;
186 }
187
188 return 0;
189 }
190
191 // Otherwise, we failed.
192 return 0;
Chris Lattner210e45a2009-12-04 02:10:16 +0000193}
194
Chris Lattner9a864122009-12-07 18:36:53 +0000195
196/// PHITranslateValue - PHI translate the current address up the CFG from
197/// CurBB to Pred, updating our state the reflect any needed changes. This
Chris Lattnere05a1882009-12-07 19:45:30 +0000198/// returns true on failure and sets Addr to null.
Chris Lattner9a864122009-12-07 18:36:53 +0000199bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB) {
200 Addr = PHITranslateSubExpr(Addr, CurBB, PredBB);
201 return Addr == 0;
202}
203
204/// GetAvailablePHITranslatedSubExpr - Return the value computed by
205/// PHITranslateSubExpr if it dominates PredBB, otherwise return null.
Chris Lattner210e45a2009-12-04 02:10:16 +0000206Value *PHITransAddr::
Chris Lattner9a864122009-12-07 18:36:53 +0000207GetAvailablePHITranslatedSubExpr(Value *V, BasicBlock *CurBB,BasicBlock *PredBB,
208 const DominatorTree &DT) {
Chris Lattner210e45a2009-12-04 02:10:16 +0000209 // See if PHI translation succeeds.
Chris Lattner9a864122009-12-07 18:36:53 +0000210 V = PHITranslateSubExpr(V, CurBB, PredBB);
Chris Lattner210e45a2009-12-04 02:10:16 +0000211
212 // Make sure the value is live in the predecessor.
213 if (Instruction *Inst = dyn_cast_or_null<Instruction>(V))
214 if (!DT.dominates(Inst->getParent(), PredBB))
215 return 0;
216 return V;
217}
218
Chris Lattner9a864122009-12-07 18:36:53 +0000219
220/// PHITranslateWithInsertion - PHI translate this value into the specified
221/// predecessor block, inserting a computation of the value if it is
222/// unavailable.
223///
224/// All newly created instructions are added to the NewInsts list. This
225/// returns null on failure.
226///
227Value *PHITransAddr::
228PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
229 const DominatorTree &DT,
230 SmallVectorImpl<Instruction*> &NewInsts) {
231 unsigned NISize = NewInsts.size();
232
233 // Attempt to PHI translate with insertion.
234 Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts);
235
236 // If successful, return the new value.
237 if (Addr) return Addr;
238
239 // If not, destroy any intermediate instructions inserted.
240 while (NewInsts.size() != NISize)
241 NewInsts.pop_back_val()->eraseFromParent();
242 return 0;
243}
244
245
Chris Lattner210e45a2009-12-04 02:10:16 +0000246/// InsertPHITranslatedPointer - Insert a computation of the PHI translated
247/// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
248/// block. All newly created instructions are added to the NewInsts list.
249/// This returns null on failure.
250///
251Value *PHITransAddr::
Chris Lattner9a864122009-12-07 18:36:53 +0000252InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
253 BasicBlock *PredBB, const DominatorTree &DT,
254 SmallVectorImpl<Instruction*> &NewInsts) {
Chris Lattner210e45a2009-12-04 02:10:16 +0000255 // See if we have a version of this value already available and dominating
Chris Lattner9a864122009-12-07 18:36:53 +0000256 // PredBB. If so, there is no need to insert a new instance of it.
257 if (Value *Res = GetAvailablePHITranslatedSubExpr(InVal, CurBB, PredBB, DT))
Chris Lattner210e45a2009-12-04 02:10:16 +0000258 return Res;
259
Chris Lattner9a864122009-12-07 18:36:53 +0000260 // If we don't have an available version of this value, it must be an
261 // instruction.
262 Instruction *Inst = cast<Instruction>(InVal);
263
264 // Handle bitcast of PHI translatable value.
265 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
266 Value *OpVal = InsertPHITranslatedSubExpr(BC->getOperand(0),
267 CurBB, PredBB, DT, NewInsts);
268 if (OpVal == 0) return 0;
269
270 // Otherwise insert a bitcast at the end of PredBB.
271 BitCastInst *New = new BitCastInst(OpVal, InVal->getType(),
272 InVal->getName()+".phi.trans.insert",
273 PredBB->getTerminator());
274 NewInsts.push_back(New);
275 return New;
276 }
277
278 // Handle getelementptr with at least one PHI operand.
279 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
280 SmallVector<Value*, 8> GEPOps;
281 BasicBlock *CurBB = GEP->getParent();
282 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
283 Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i),
284 CurBB, PredBB, DT, NewInsts);
285 if (OpVal == 0) return 0;
286 GEPOps.push_back(OpVal);
287 }
288
289 GetElementPtrInst *Result =
290 GetElementPtrInst::Create(GEPOps[0], GEPOps.begin()+1, GEPOps.end(),
291 InVal->getName()+".phi.trans.insert",
292 PredBB->getTerminator());
293 Result->setIsInBounds(GEP->isInBounds());
294 NewInsts.push_back(Result);
295 return Result;
296 }
297
298#if 0
299 // FIXME: This code works, but it is unclear that we actually want to insert
300 // a big chain of computation in order to make a value available in a block.
301 // This needs to be evaluated carefully to consider its cost trade offs.
302
303 // Handle add with a constant RHS.
304 if (Inst->getOpcode() == Instruction::Add &&
305 isa<ConstantInt>(Inst->getOperand(1))) {
306 // PHI translate the LHS.
307 Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0),
308 CurBB, PredBB, DT, NewInsts);
309 if (OpVal == 0) return 0;
310
311 BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1),
312 InVal->getName()+".phi.trans.insert",
313 PredBB->getTerminator());
314 Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap());
315 Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap());
316 NewInsts.push_back(Res);
317 return Res;
318 }
319#endif
320
Chris Lattner210e45a2009-12-04 02:10:16 +0000321 return 0;
322}