1 //===- LevelRaise.cpp - Code to change LLVM to higher level -----------------=//
3 // This file implements the 'raising' part of the LevelChange API. This is
4 // useful because, in general, it makes the LLVM code terser and easier to
7 //===----------------------------------------------------------------------===//
9 #include "llvm/Transforms/LevelChange.h"
10 #include "llvm/Transforms/Utils/Local.h"
11 #include "TransformInternals.h"
12 #include "llvm/iOther.h"
13 #include "llvm/iMemory.h"
14 #include "llvm/Pass.h"
15 #include "llvm/ConstantHandling.h"
16 #include "llvm/Analysis/Expressions.h"
17 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
18 #include "Support/STLExtras.h"
19 #include "Support/StatisticReporter.h"
22 static Statistic<> NumLoadStorePeepholes("raise\t\t- Number of load/store peepholes");
23 static Statistic<> NumGEPInstFormed("raise\t\t- Number of other getelementptr's formed");
24 static Statistic<> NumExprTreesConv("raise\t\t- Number of expression trees converted");
25 static Statistic<> NumCastOfCast("raise\t\t- Number of cast-of-self removed");
26 static Statistic<> NumDCEorCP("raise\t\t- Number of insts DCE'd or constprop'd");
29 #define PRINT_PEEPHOLE(ID, NUM, I) \
30 DEBUG(std::cerr << "Inst P/H " << ID << "[" << NUM << "] " << I)
32 #define PRINT_PEEPHOLE1(ID, I1) do { PRINT_PEEPHOLE(ID, 0, I1); } while (0)
33 #define PRINT_PEEPHOLE2(ID, I1, I2) \
34 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); } while (0)
35 #define PRINT_PEEPHOLE3(ID, I1, I2, I3) \
36 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
37 PRINT_PEEPHOLE(ID, 2, I3); } while (0)
38 #define PRINT_PEEPHOLE4(ID, I1, I2, I3, I4) \
39 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
40 PRINT_PEEPHOLE(ID, 2, I3); PRINT_PEEPHOLE(ID, 3, I4); } while (0)
43 // isReinterpretingCast - Return true if the cast instruction specified will
44 // cause the operand to be "reinterpreted". A value is reinterpreted if the
45 // cast instruction would cause the underlying bits to change.
47 static inline bool isReinterpretingCast(const CastInst *CI) {
48 return!CI->getOperand(0)->getType()->isLosslesslyConvertableTo(CI->getType());
52 // Peephole optimize the following instructions:
53 // %t1 = cast ? to x *
54 // %t2 = add x * %SP, %t1 ;; Constant must be 2nd operand
56 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
57 // %t2 = cast <eltype> * %t3 to {<...>}*
59 static bool HandleCastToPointer(BasicBlock::iterator BI,
60 const PointerType *DestPTy) {
61 CastInst *CI = cast<CastInst>(*BI);
62 if (CI->use_empty()) return false;
64 // Scan all of the uses, looking for any uses that are not add
65 // instructions. If we have non-adds, do not make this transformation.
67 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
69 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
70 if (BO->getOpcode() != Instruction::Add)
77 std::vector<Value*> Indices;
78 Value *Src = CI->getOperand(0);
79 const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
80 if (Result == 0) return false; // Not convertable...
82 PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);
84 // If we have a getelementptr capability... transform all of the
85 // add instruction uses into getelementptr's.
86 while (!CI->use_empty()) {
87 BinaryOperator *I = cast<BinaryOperator>(*CI->use_begin());
88 assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
89 "Use is not a valid add instruction!");
91 // Get the value added to the cast result pointer...
92 Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);
94 Instruction *GEP = new GetElementPtrInst(OtherPtr, Indices, I->getName());
95 PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
97 if (GEP->getType() == I->getType()) {
98 // Replace the old add instruction with the shiny new GEP inst
99 ReplaceInstWithInst(I, GEP);
101 // If the type produced by the gep instruction differs from the original
102 // add instruction type, insert a cast now.
105 // Insert the GEP instruction before the old add instruction... and get an
106 // iterator to point at the add instruction...
107 BasicBlock::iterator GEPI = InsertInstBeforeInst(GEP, I)+1;
109 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
110 CastInst *CI = new CastInst(GEP, I->getType());
113 // Replace the old add instruction with the shiny new GEP inst
114 ReplaceInstWithInst(I->getParent()->getInstList(), GEPI, GEP);
117 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
122 // Peephole optimize the following instructions:
123 // %t1 = cast ulong <const int> to {<...>} *
124 // %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
127 // %t1 = cast {<...>}* %SP to int*
128 // %t5 = cast ulong <const int> to int*
129 // %t2 = add int* %t1, %t5 ;; int is same size as field
131 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
132 // %t2 = cast <eltype> * %t3 to {<...>}*
134 static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
135 Value *AddOp1, CastInst *AddOp2) {
136 const CompositeType *CompTy;
137 Value *OffsetVal = AddOp2->getOperand(0);
138 Value *SrcPtr; // Of type pointer to struct...
140 if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
141 SrcPtr = AddOp1; // Handle the first case...
142 } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
143 SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
144 CompTy = getPointedToComposite(SrcPtr->getType());
147 // Only proceed if we have detected all of our conditions successfully...
148 if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
151 std::vector<Value*> Indices;
152 if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
153 return false; // Not convertable... perhaps next time
155 if (getPointedToComposite(AddOp1->getType())) { // case 1
156 PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
158 PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
161 GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
163 BI = BB->getInstList().insert(BI, GEP)+1;
165 Instruction *NCI = new CastInst(GEP, AddOp1->getType());
166 ReplaceInstWithInst(BB->getInstList(), BI, NCI);
167 PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
171 static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
172 Instruction *I = *BI;
174 if (CastInst *CI = dyn_cast<CastInst>(I)) {
175 Value *Src = CI->getOperand(0);
176 Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
177 const Type *DestTy = CI->getType();
179 // Peephole optimize the following instruction:
180 // %V2 = cast <ty> %V to <ty>
184 if (DestTy == Src->getType()) { // Check for a cast to same type as src!!
185 PRINT_PEEPHOLE1("cast-of-self-ty", CI);
186 CI->replaceAllUsesWith(Src);
187 if (!Src->hasName() && CI->hasName()) {
188 std::string Name = CI->getName();
190 Src->setName(Name, BB->getParent()->getSymbolTable());
193 // DCE the instruction now, to avoid having the iterative version of DCE
194 // have to worry about it.
196 delete BB->getInstList().remove(BI);
202 // Check to see if it's a cast of an instruction that does not depend on the
203 // specific type of the operands to do it's job.
204 if (!isReinterpretingCast(CI)) {
205 ValueTypeCache ConvertedTypes;
207 // Check to see if we can convert the source of the cast to match the
208 // destination type of the cast...
210 ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
211 if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
212 PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", Src, CI, BB->getParent());
214 DEBUG(cerr << "\nCONVERTING SRC EXPR TYPE:\n");
215 ValueMapCache ValueMap;
216 Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
217 if (Constant *CPV = dyn_cast<Constant>(E))
218 CI->replaceAllUsesWith(CPV);
220 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
221 PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", E);
222 DEBUG(cerr << "DONE CONVERTING SRC EXPR TYPE: \n" << BB->getParent());
227 // Check to see if we can convert the users of the cast value to match the
228 // source type of the cast...
230 ConvertedTypes.clear();
231 if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
232 PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", Src, CI, BB->getParent());
234 DEBUG(cerr << "\nCONVERTING EXPR TYPE:\n");
235 ValueMapCache ValueMap;
236 ConvertValueToNewType(CI, Src, ValueMap); // This will delete CI!
238 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
239 PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
240 DEBUG(cerr << "DONE CONVERTING EXPR TYPE: \n\n" << BB->getParent());
246 // Otherwise find out it this cast is a cast to a pointer type, which is
247 // then added to some other pointer, then loaded or stored through. If
248 // so, convert the add into a getelementptr instruction...
250 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
251 if (HandleCastToPointer(BI, DestPTy)) {
252 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
258 // Check to see if we are casting from a structure pointer to a pointer to
259 // the first element of the structure... to avoid munching other peepholes,
260 // we only let this happen if there are no add uses of the cast.
262 // Peephole optimize the following instructions:
263 // %t1 = cast {<...>} * %StructPtr to <ty> *
265 // Into: %t2 = getelementptr {<...>} * %StructPtr, <0, 0, 0, ...>
266 // %t1 = cast <eltype> * %t1 to <ty> *
268 if (const CompositeType *CTy = getPointedToComposite(Src->getType()))
269 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
271 // Loop over uses of the cast, checking for add instructions. If an add
272 // exists, this is probably a part of a more complex GEP, so we don't
273 // want to mess around with the cast.
275 bool HasAddUse = false;
276 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
278 if (isa<Instruction>(*I) &&
279 cast<Instruction>(*I)->getOpcode() == Instruction::Add) {
280 HasAddUse = true; break;
283 // If it doesn't have an add use, check to see if the dest type is
284 // losslessly convertable to one of the types in the start of the struct
288 const Type *DestPointedTy = DestPTy->getElementType();
290 const CompositeType *CurCTy = CTy;
291 const Type *ElTy = 0;
293 // Build the index vector, full of all zeros
294 std::vector<Value*> Indices;
295 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
296 while (CurCTy && !isa<PointerType>(CurCTy)) {
297 if (const StructType *CurSTy = dyn_cast<StructType>(CurCTy)) {
298 // Check for a zero element struct type... if we have one, bail.
299 if (CurSTy->getElementTypes().size() == 0) break;
301 // Grab the first element of the struct type, which must lie at
302 // offset zero in the struct.
304 ElTy = CurSTy->getElementTypes()[0];
306 ElTy = cast<ArrayType>(CurCTy)->getElementType();
309 // Insert a zero to index through this type...
310 Indices.push_back(ConstantUInt::get(CurCTy->getIndexType(), 0));
312 // Did we find what we're looking for?
313 if (ElTy->isLosslesslyConvertableTo(DestPointedTy)) break;
315 // Nope, go a level deeper.
317 CurCTy = dyn_cast<CompositeType>(ElTy);
321 // Did we find what we were looking for? If so, do the transformation
323 PRINT_PEEPHOLE1("cast-for-first:in", CI);
325 // Insert the new T cast instruction... stealing old T's name
326 GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
329 BI = BB->getInstList().insert(BI, GEP)+1;
331 // Make the old cast instruction reference the new GEP instead of
332 // the old src value.
334 CI->setOperand(0, GEP);
336 PRINT_PEEPHOLE2("cast-for-first:out", GEP, CI);
343 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
344 Value *Val = SI->getOperand(0);
345 Value *Pointer = SI->getPointerOperand();
347 // Peephole optimize the following instructions:
348 // %t = cast <T1>* %P to <T2> * ;; If T1 is losslessly convertable to T2
349 // store <T2> %V, <T2>* %t
352 // %t = cast <T2> %V to <T1>
353 // store <T1> %t2, <T1>* %P
355 // Note: This is not taken care of by expr conversion because there might
356 // not be a cast available for the store to convert the incoming value of.
357 // This code is basically here to make sure that pointers don't have casts
360 if (CastInst *CI = dyn_cast<CastInst>(Pointer))
361 if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
362 if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
363 // convertable types?
364 if (Val->getType()->isLosslesslyConvertableTo(CSPT->getElementType()) &&
365 !SI->hasIndices()) { // No subscripts yet!
366 PRINT_PEEPHOLE3("st-src-cast:in ", Pointer, Val, SI);
368 // Insert the new T cast instruction... stealing old T's name
369 CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
372 BI = BB->getInstList().insert(BI, NCI)+1;
374 // Replace the old store with a new one!
375 ReplaceInstWithInst(BB->getInstList(), BI,
376 SI = new StoreInst(NCI, CastSrc));
377 PRINT_PEEPHOLE3("st-src-cast:out", NCI, CastSrc, SI);
378 ++NumLoadStorePeepholes;
382 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
383 Value *Pointer = LI->getOperand(0);
384 const Type *PtrElType =
385 cast<PointerType>(Pointer->getType())->getElementType();
387 // Peephole optimize the following instructions:
388 // %Val = cast <T1>* to <T2>* ;; If T1 is losslessly convertable to T2
389 // %t = load <T2>* %P
392 // %t = load <T1>* %P
393 // %Val = cast <T1> to <T2>
395 // Note: This is not taken care of by expr conversion because there might
396 // not be a cast available for the store to convert the incoming value of.
397 // This code is basically here to make sure that pointers don't have casts
400 if (CastInst *CI = dyn_cast<CastInst>(Pointer))
401 if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
402 if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
403 // convertable types?
404 if (PtrElType->isLosslesslyConvertableTo(CSPT->getElementType()) &&
405 !LI->hasIndices()) { // No subscripts yet!
406 PRINT_PEEPHOLE2("load-src-cast:in ", Pointer, LI);
408 // Create the new load instruction... loading the pre-casted value
409 LoadInst *NewLI = new LoadInst(CastSrc, LI->getName());
411 // Insert the new T cast instruction... stealing old T's name
412 CastInst *NCI = new CastInst(NewLI, LI->getType(), CI->getName());
413 BI = BB->getInstList().insert(BI, NewLI)+1;
415 // Replace the old store with a new one!
416 ReplaceInstWithInst(BB->getInstList(), BI, NCI);
417 PRINT_PEEPHOLE3("load-src-cast:out", NCI, CastSrc, NewLI);
418 ++NumLoadStorePeepholes;
422 } else if (I->getOpcode() == Instruction::Add &&
423 isa<CastInst>(I->getOperand(1))) {
425 if (PeepholeOptimizeAddCast(BB, BI, I->getOperand(0),
426 cast<CastInst>(I->getOperand(1)))) {
438 static bool DoRaisePass(Function *F) {
439 bool Changed = false;
440 for (Function::iterator MI = F->begin(), ME = F->end(); MI != ME; ++MI) {
441 BasicBlock *BB = *MI;
442 BasicBlock::InstListType &BIL = BB->getInstList();
444 for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
445 DEBUG(cerr << "Processing: " << *BI);
446 if (dceInstruction(BIL, BI) || doConstantPropogation(BB, BI)) {
449 DEBUG(cerr << "***\t\t^^-- DeadCode Elinated!\n");
450 } else if (PeepholeOptimize(BB, BI))
460 // RaisePointerReferences::doit - Raise a function representation to a higher
463 static bool doRPR(Function *F) {
464 DEBUG(cerr << "\n\n\nStarting to work on Function '" << F->getName()<< "'\n");
466 // Insert casts for all incoming pointer pointer values that are treated as
469 bool Changed = false, LocalChange;
472 DEBUG(cerr << "Looping: \n" << F);
474 // Iterate over the function, refining it, until it converges on a stable
477 while (DoRaisePass(F)) LocalChange = true;
478 Changed |= LocalChange;
480 } while (LocalChange);
486 struct RaisePointerReferences : public FunctionPass {
487 const char *getPassName() const { return "Raise Pointer References"; }
489 virtual bool runOnFunction(Function *F) { return doRPR(F); }
491 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
497 Pass *createRaisePointerReferencesPass() {
498 return new RaisePointerReferences();