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"
21 //#define DEBUG_PEEPHOLE_INSTS 1
23 #ifdef DEBUG_PEEPHOLE_INSTS
24 #define PRINT_PEEPHOLE(ID, NUM, I) \
25 std::cerr << "Inst P/H " << ID << "[" << NUM << "] " << I;
27 #define PRINT_PEEPHOLE(ID, NUM, I)
30 #define PRINT_PEEPHOLE1(ID, I1) do { PRINT_PEEPHOLE(ID, 0, I1); } while (0)
31 #define PRINT_PEEPHOLE2(ID, I1, I2) \
32 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); } while (0)
33 #define PRINT_PEEPHOLE3(ID, I1, I2, I3) \
34 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
35 PRINT_PEEPHOLE(ID, 2, I3); } while (0)
36 #define PRINT_PEEPHOLE4(ID, I1, I2, I3, I4) \
37 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
38 PRINT_PEEPHOLE(ID, 2, I3); PRINT_PEEPHOLE(ID, 3, I4); } while (0)
41 // isReinterpretingCast - Return true if the cast instruction specified will
42 // cause the operand to be "reinterpreted". A value is reinterpreted if the
43 // cast instruction would cause the underlying bits to change.
45 static inline bool isReinterpretingCast(const CastInst *CI) {
46 return!CI->getOperand(0)->getType()->isLosslesslyConvertableTo(CI->getType());
50 // Peephole optimize the following instructions:
51 // %t1 = cast ? to x *
52 // %t2 = add x * %SP, %t1 ;; Constant must be 2nd operand
54 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
55 // %t2 = cast <eltype> * %t3 to {<...>}*
57 static bool HandleCastToPointer(BasicBlock::iterator BI,
58 const PointerType *DestPTy) {
59 CastInst *CI = cast<CastInst>(*BI);
60 if (CI->use_empty()) return false;
62 // Scan all of the uses, looking for any uses that are not add
63 // instructions. If we have non-adds, do not make this transformation.
65 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
67 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
68 if (BO->getOpcode() != Instruction::Add)
75 std::vector<Value*> Indices;
76 Value *Src = CI->getOperand(0);
77 const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
78 if (Result == 0) return false; // Not convertable...
80 PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);
82 // If we have a getelementptr capability... transform all of the
83 // add instruction uses into getelementptr's.
84 while (!CI->use_empty()) {
85 BinaryOperator *I = cast<BinaryOperator>(*CI->use_begin());
86 assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
87 "Use is not a valid add instruction!");
89 // Get the value added to the cast result pointer...
90 Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);
92 Instruction *GEP = new GetElementPtrInst(OtherPtr, Indices, I->getName());
93 PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
95 if (GEP->getType() == I->getType()) {
96 // Replace the old add instruction with the shiny new GEP inst
97 ReplaceInstWithInst(I, GEP);
99 // If the type produced by the gep instruction differs from the original
100 // add instruction type, insert a cast now.
103 // Insert the GEP instruction before the old add instruction... and get an
104 // iterator to point at the add instruction...
105 BasicBlock::iterator GEPI = InsertInstBeforeInst(GEP, I)+1;
107 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
108 CastInst *CI = new CastInst(GEP, I->getType());
111 // Replace the old add instruction with the shiny new GEP inst
112 ReplaceInstWithInst(I->getParent()->getInstList(), GEPI, GEP);
115 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
120 // Peephole optimize the following instructions:
121 // %t1 = cast ulong <const int> to {<...>} *
122 // %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
125 // %t1 = cast {<...>}* %SP to int*
126 // %t5 = cast ulong <const int> to int*
127 // %t2 = add int* %t1, %t5 ;; int is same size as field
129 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
130 // %t2 = cast <eltype> * %t3 to {<...>}*
132 static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
133 Value *AddOp1, CastInst *AddOp2) {
134 const CompositeType *CompTy;
135 Value *OffsetVal = AddOp2->getOperand(0);
136 Value *SrcPtr; // Of type pointer to struct...
138 if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
139 SrcPtr = AddOp1; // Handle the first case...
140 } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
141 SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
142 CompTy = getPointedToComposite(SrcPtr->getType());
145 // Only proceed if we have detected all of our conditions successfully...
146 if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
149 std::vector<Value*> Indices;
150 if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
151 return false; // Not convertable... perhaps next time
153 if (getPointedToComposite(AddOp1->getType())) { // case 1
154 PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
156 PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
159 GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
161 BI = BB->getInstList().insert(BI, GEP)+1;
163 Instruction *NCI = new CastInst(GEP, AddOp1->getType());
164 ReplaceInstWithInst(BB->getInstList(), BI, NCI);
165 PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
169 static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
170 Instruction *I = *BI;
172 if (CastInst *CI = dyn_cast<CastInst>(I)) {
173 Value *Src = CI->getOperand(0);
174 Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
175 const Type *DestTy = CI->getType();
177 // Peephole optimize the following instruction:
178 // %V2 = cast <ty> %V to <ty>
182 if (DestTy == Src->getType()) { // Check for a cast to same type as src!!
183 PRINT_PEEPHOLE1("cast-of-self-ty", CI);
184 CI->replaceAllUsesWith(Src);
185 if (!Src->hasName() && CI->hasName()) {
186 std::string Name = CI->getName();
188 Src->setName(Name, BB->getParent()->getSymbolTable());
193 // Check to see if it's a cast of an instruction that does not depend on the
194 // specific type of the operands to do it's job.
195 if (!isReinterpretingCast(CI)) {
196 ValueTypeCache ConvertedTypes;
198 // Check to see if we can convert the users of the cast value to match the
199 // source type of the cast...
201 ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
202 if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
203 PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", Src, CI, BB->getParent());
205 #ifdef DEBUG_PEEPHOLE_INSTS
206 cerr << "\nCONVERTING SRC EXPR TYPE:\n";
208 ValueMapCache ValueMap;
209 Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
210 if (Constant *CPV = dyn_cast<Constant>(E))
211 CI->replaceAllUsesWith(CPV);
213 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
214 PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", E);
215 #ifdef DEBUG_PEEPHOLE_INSTS
216 cerr << "DONE CONVERTING SRC EXPR TYPE: \n" << BB->getParent();
221 // Check to see if we can convert the source of the cast to match the
222 // destination type of the cast...
224 ConvertedTypes.clear();
225 if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
226 PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", Src, CI, BB->getParent());
228 #ifdef DEBUG_PEEPHOLE_INSTS
229 cerr << "\nCONVERTING EXPR TYPE:\n";
231 ValueMapCache ValueMap;
232 ConvertValueToNewType(CI, Src, ValueMap); // This will delete CI!
234 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
235 PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
236 #ifdef DEBUG_PEEPHOLE_INSTS
237 cerr << "DONE CONVERTING EXPR TYPE: \n\n" << BB->getParent();
243 // Otherwise find out it this cast is a cast to a pointer type, which is
244 // then added to some other pointer, then loaded or stored through. If
245 // so, convert the add into a getelementptr instruction...
247 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
248 if (HandleCastToPointer(BI, DestPTy)) {
249 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
254 // Check to see if we are casting from a structure pointer to a pointer to
255 // the first element of the structure... to avoid munching other peepholes,
256 // we only let this happen if there are no add uses of the cast.
258 // Peephole optimize the following instructions:
259 // %t1 = cast {<...>} * %StructPtr to <ty> *
261 // Into: %t2 = getelementptr {<...>} * %StructPtr, <0, 0, 0, ...>
262 // %t1 = cast <eltype> * %t1 to <ty> *
265 if (const CompositeType *CTy = getPointedToComposite(Src->getType()))
266 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
268 // Loop over uses of the cast, checking for add instructions. If an add
269 // exists, this is probably a part of a more complex GEP, so we don't
270 // want to mess around with the cast.
272 bool HasAddUse = false;
273 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
275 if (isa<Instruction>(*I) &&
276 cast<Instruction>(*I)->getOpcode() == Instruction::Add) {
277 HasAddUse = true; break;
280 // If it doesn't have an add use, check to see if the dest type is
281 // losslessly convertable to one of the types in the start of the struct
285 const Type *DestPointedTy = DestPTy->getElementType();
287 const CompositeType *CurCTy = CTy;
288 const Type *ElTy = 0;
290 // Build the index vector, full of all zeros
291 std::vector<Value*> Indices;
292 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
293 while (CurCTy && !isa<PointerType>(CurCTy)) {
294 if (const StructType *CurSTy = dyn_cast<StructType>(CurCTy)) {
295 // Check for a zero element struct type... if we have one, bail.
296 if (CurSTy->getElementTypes().size() == 0) break;
298 // Grab the first element of the struct type, which must lie at
299 // offset zero in the struct.
301 ElTy = CurSTy->getElementTypes()[0];
303 ElTy = cast<ArrayType>(CurCTy)->getElementType();
306 // Insert a zero to index through this type...
307 Indices.push_back(ConstantUInt::get(CurCTy->getIndexType(), 0));
309 // Did we find what we're looking for?
310 if (ElTy->isLosslesslyConvertableTo(DestPointedTy)) break;
312 // Nope, go a level deeper.
314 CurCTy = dyn_cast<CompositeType>(ElTy);
318 // Did we find what we were looking for? If so, do the transformation
320 PRINT_PEEPHOLE1("cast-for-first:in", CI);
322 // Insert the new T cast instruction... stealing old T's name
323 GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
326 BI = BB->getInstList().insert(BI, GEP)+1;
328 // Make the old cast instruction reference the new GEP instead of
329 // the old src value.
331 CI->setOperand(0, GEP);
333 PRINT_PEEPHOLE2("cast-for-first:out", GEP, CI);
341 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
342 Value *Val = SI->getOperand(0);
343 Value *Pointer = SI->getPointerOperand();
345 // Peephole optimize the following instructions:
346 // %t = cast <T1>* %P to <T2> * ;; If T1 is losslessly convertable to T2
347 // store <T2> %V, <T2>* %t
350 // %t = cast <T2> %V to <T1>
351 // store <T1> %t2, <T1>* %P
353 // Note: This is not taken care of by expr conversion because there might
354 // not be a cast available for the store to convert the incoming value of.
355 // This code is basically here to make sure that pointers don't have casts
358 if (CastInst *CI = dyn_cast<CastInst>(Pointer))
359 if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
360 if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
361 // convertable types?
362 if (Val->getType()->isLosslesslyConvertableTo(CSPT->getElementType()) &&
363 !SI->hasIndices()) { // No subscripts yet!
364 PRINT_PEEPHOLE3("st-src-cast:in ", Pointer, Val, SI);
366 // Insert the new T cast instruction... stealing old T's name
367 CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
370 BI = BB->getInstList().insert(BI, NCI)+1;
372 // Replace the old store with a new one!
373 ReplaceInstWithInst(BB->getInstList(), BI,
374 SI = new StoreInst(NCI, CastSrc));
375 PRINT_PEEPHOLE3("st-src-cast:out", NCI, CastSrc, SI);
379 } else if (I->getOpcode() == Instruction::Add &&
380 isa<CastInst>(I->getOperand(1))) {
382 if (PeepholeOptimizeAddCast(BB, BI, I->getOperand(0),
383 cast<CastInst>(I->getOperand(1))))
395 static bool DoRaisePass(Function *F) {
396 bool Changed = false;
397 for (Function::iterator MI = F->begin(), ME = F->end(); MI != ME; ++MI) {
398 BasicBlock *BB = *MI;
399 BasicBlock::InstListType &BIL = BB->getInstList();
401 for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
402 #if DEBUG_PEEPHOLE_INSTS
403 cerr << "Processing: " << *BI;
405 if (dceInstruction(BIL, BI) || doConstantPropogation(BB, BI)) {
407 #ifdef DEBUG_PEEPHOLE_INSTS
408 cerr << "***\t\t^^-- DeadCode Elinated!\n";
410 } else if (PeepholeOptimize(BB, BI))
420 // RaisePointerReferences::doit - Raise a function representation to a higher
423 static bool doRPR(Function *F) {
424 #ifdef DEBUG_PEEPHOLE_INSTS
425 cerr << "\n\n\nStarting to work on Function '" << F->getName() << "'\n";
428 // Insert casts for all incoming pointer pointer values that are treated as
431 bool Changed = false, LocalChange;
434 #ifdef DEBUG_PEEPHOLE_INSTS
435 cerr << "Looping: \n" << F;
438 // Iterate over the function, refining it, until it converges on a stable
441 while (DoRaisePass(F)) LocalChange = true;
442 Changed |= LocalChange;
444 } while (LocalChange);
450 struct RaisePointerReferences : public FunctionPass {
451 const char *getPassName() const { return "Raise Pointer References"; }
453 virtual bool runOnFunction(Function *F) { return doRPR(F); }
455 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
461 Pass *createRaisePointerReferencesPass() {
462 return new RaisePointerReferences();