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 "TransformInternals.h"
11 #include "llvm/Function.h"
12 #include "llvm/iOther.h"
13 #include "llvm/iMemory.h"
14 #include "llvm/Constants.h"
15 #include "llvm/Pass.h"
16 #include "llvm/ConstantHandling.h"
17 #include "llvm/Transforms/Scalar/DCE.h"
18 #include "llvm/Transforms/Scalar/ConstantProp.h"
19 #include "llvm/Analysis/Expressions.h"
20 #include "Support/STLExtras.h"
23 //#define DEBUG_PEEPHOLE_INSTS 1
25 #ifdef DEBUG_PEEPHOLE_INSTS
26 #define PRINT_PEEPHOLE(ID, NUM, I) \
27 std::cerr << "Inst P/H " << ID << "[" << NUM << "] " << I;
29 #define PRINT_PEEPHOLE(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());
53 // Peephole optimize the following instructions:
54 // %t1 = cast ? to x *
55 // %t2 = add x * %SP, %t1 ;; Constant must be 2nd operand
57 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
58 // %t2 = cast <eltype> * %t3 to {<...>}*
60 static bool HandleCastToPointer(BasicBlock::iterator BI,
61 const PointerType *DestPTy) {
62 CastInst *CI = cast<CastInst>(*BI);
63 if (CI->use_empty()) return false;
65 // Scan all of the uses, looking for any uses that are not add
66 // instructions. If we have non-adds, do not make this transformation.
68 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
70 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
71 if (BO->getOpcode() != Instruction::Add)
78 std::vector<Value*> Indices;
79 Value *Src = CI->getOperand(0);
80 const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
81 if (Result == 0) return false; // Not convertable...
83 PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);
85 // If we have a getelementptr capability... transform all of the
86 // add instruction uses into getelementptr's.
87 while (!CI->use_empty()) {
88 BinaryOperator *I = cast<BinaryOperator>(*CI->use_begin());
89 assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
90 "Use is not a valid add instruction!");
92 // Get the value added to the cast result pointer...
93 Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);
95 Instruction *GEP = new GetElementPtrInst(OtherPtr, Indices, I->getName());
96 PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
98 if (GEP->getType() == I->getType()) {
99 // Replace the old add instruction with the shiny new GEP inst
100 ReplaceInstWithInst(I, GEP);
102 // If the type produced by the gep instruction differs from the original
103 // add instruction type, insert a cast now.
106 // Insert the GEP instruction before the old add instruction... and get an
107 // iterator to point at the add instruction...
108 BasicBlock::iterator GEPI = InsertInstBeforeInst(GEP, I)+1;
110 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
111 CastInst *CI = new CastInst(GEP, I->getType());
114 // Replace the old add instruction with the shiny new GEP inst
115 ReplaceInstWithInst(I->getParent()->getInstList(), GEPI, GEP);
118 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
123 // Peephole optimize the following instructions:
124 // %t1 = cast ulong <const int> to {<...>} *
125 // %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
128 // %t1 = cast {<...>}* %SP to int*
129 // %t5 = cast ulong <const int> to int*
130 // %t2 = add int* %t1, %t5 ;; int is same size as field
132 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
133 // %t2 = cast <eltype> * %t3 to {<...>}*
135 static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
136 Value *AddOp1, CastInst *AddOp2) {
137 const CompositeType *CompTy;
138 Value *OffsetVal = AddOp2->getOperand(0);
139 Value *SrcPtr; // Of type pointer to struct...
141 if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
142 SrcPtr = AddOp1; // Handle the first case...
143 } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
144 SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
145 CompTy = getPointedToComposite(SrcPtr->getType());
148 // Only proceed if we have detected all of our conditions successfully...
149 if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
152 std::vector<Value*> Indices;
153 if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
154 return false; // Not convertable... perhaps next time
156 if (getPointedToComposite(AddOp1->getType())) { // case 1
157 PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
159 PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
162 GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
164 BI = BB->getInstList().insert(BI, GEP)+1;
166 Instruction *NCI = new CastInst(GEP, AddOp1->getType());
167 ReplaceInstWithInst(BB->getInstList(), BI, NCI);
168 PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
172 static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
173 Instruction *I = *BI;
175 if (CastInst *CI = dyn_cast<CastInst>(I)) {
176 Value *Src = CI->getOperand(0);
177 Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
178 const Type *DestTy = CI->getType();
180 // Peephole optimize the following instruction:
181 // %V2 = cast <ty> %V to <ty>
185 if (DestTy == Src->getType()) { // Check for a cast to same type as src!!
186 PRINT_PEEPHOLE1("cast-of-self-ty", CI);
187 CI->replaceAllUsesWith(Src);
188 if (!Src->hasName() && CI->hasName()) {
189 std::string Name = CI->getName();
191 Src->setName(Name, BB->getParent()->getSymbolTable());
196 // Peephole optimize the following instructions:
197 // %tmp = cast <ty> %V to <ty2>
198 // %V = cast <ty2> %tmp to <ty3> ; Where ty & ty2 are same size
200 // Into: cast <ty> %V to <ty3>
203 if (CastInst *CSrc = dyn_cast<CastInst>(SrcI))
204 if (isReinterpretingCast(CI) + isReinterpretingCast(CSrc) < 2) {
205 // We can only do c-c elimination if, at most, one cast does a
206 // reinterpretation of the input data.
208 // If legal, make this cast refer the the original casts argument!
210 PRINT_PEEPHOLE2("cast-cast:in ", CI, CSrc);
211 CI->setOperand(0, CSrc->getOperand(0));
212 PRINT_PEEPHOLE1("cast-cast:out", CI);
216 // Check to see if it's a cast of an instruction that does not depend on the
217 // specific type of the operands to do it's job.
218 if (!isReinterpretingCast(CI)) {
219 ValueTypeCache ConvertedTypes;
221 // Check to see if we can convert the users of the cast value to match the
222 // source type of the cast...
224 ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
225 if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
226 PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", Src, CI, BB->getParent());
228 #ifdef DEBUG_PEEPHOLE_INSTS
229 cerr << "\nCONVERTING SRC EXPR TYPE:\n";
231 ValueMapCache ValueMap;
232 Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
233 if (Constant *CPV = dyn_cast<Constant>(E))
234 CI->replaceAllUsesWith(CPV);
236 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
237 PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", E);
238 #ifdef DEBUG_PEEPHOLE_INSTS
239 cerr << "DONE CONVERTING SRC EXPR TYPE: \n" << BB->getParent();
244 // Check to see if we can convert the source of the cast to match the
245 // destination type of the cast...
247 ConvertedTypes.clear();
248 if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
249 PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", Src, CI, BB->getParent());
251 #ifdef DEBUG_PEEPHOLE_INSTS
252 cerr << "\nCONVERTING EXPR TYPE:\n";
254 ValueMapCache ValueMap;
255 ConvertValueToNewType(CI, Src, ValueMap); // This will delete CI!
257 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
258 PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
259 #ifdef DEBUG_PEEPHOLE_INSTS
260 cerr << "DONE CONVERTING EXPR TYPE: \n\n" << BB->getParent();
266 // Otherwise find out it this cast is a cast to a pointer type, which is
267 // then added to some other pointer, then loaded or stored through. If
268 // so, convert the add into a getelementptr instruction...
270 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
271 if (HandleCastToPointer(BI, DestPTy)) {
272 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
277 // Check to see if we are casting from a structure pointer to a pointer to
278 // the first element of the structure... to avoid munching other peepholes,
279 // we only let this happen if there are no add uses of the cast.
281 // Peephole optimize the following instructions:
282 // %t1 = cast {<...>} * %StructPtr to <ty> *
284 // Into: %t2 = getelementptr {<...>} * %StructPtr, <0, 0, 0, ...>
285 // %t1 = cast <eltype> * %t1 to <ty> *
288 if (const CompositeType *CTy = getPointedToComposite(Src->getType()))
289 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
291 // Loop over uses of the cast, checking for add instructions. If an add
292 // exists, this is probably a part of a more complex GEP, so we don't
293 // want to mess around with the cast.
295 bool HasAddUse = false;
296 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
298 if (isa<Instruction>(*I) &&
299 cast<Instruction>(*I)->getOpcode() == Instruction::Add) {
300 HasAddUse = true; break;
303 // If it doesn't have an add use, check to see if the dest type is
304 // losslessly convertable to one of the types in the start of the struct
308 const Type *DestPointedTy = DestPTy->getElementType();
310 const CompositeType *CurCTy = CTy;
311 const Type *ElTy = 0;
313 // Build the index vector, full of all zeros
314 std::vector<Value*> Indices;
315 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
316 while (CurCTy && !isa<PointerType>(CurCTy)) {
317 if (const StructType *CurSTy = dyn_cast<StructType>(CurCTy)) {
318 // Check for a zero element struct type... if we have one, bail.
319 if (CurSTy->getElementTypes().size() == 0) break;
321 // Grab the first element of the struct type, which must lie at
322 // offset zero in the struct.
324 ElTy = CurSTy->getElementTypes()[0];
326 ElTy = cast<ArrayType>(CurCTy)->getElementType();
329 // Insert a zero to index through this type...
330 Indices.push_back(ConstantUInt::get(CurCTy->getIndexType(), 0));
332 // Did we find what we're looking for?
333 if (ElTy->isLosslesslyConvertableTo(DestPointedTy)) break;
335 // Nope, go a level deeper.
337 CurCTy = dyn_cast<CompositeType>(ElTy);
341 // Did we find what we were looking for? If so, do the transformation
343 PRINT_PEEPHOLE1("cast-for-first:in", CI);
345 // Insert the new T cast instruction... stealing old T's name
346 GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
349 BI = BB->getInstList().insert(BI, GEP)+1;
351 // Make the old cast instruction reference the new GEP instead of
352 // the old src value.
354 CI->setOperand(0, GEP);
356 PRINT_PEEPHOLE2("cast-for-first:out", GEP, CI);
364 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
365 Value *Val = SI->getOperand(0);
366 Value *Pointer = SI->getPointerOperand();
368 // Peephole optimize the following instructions:
369 // %t = cast <T1>* %P to <T2> * ;; If T1 is losslessly convertable to T2
370 // store <T2> %V, <T2>* %t
373 // %t = cast <T2> %V to <T1>
374 // store <T1> %t2, <T1>* %P
376 // Note: This is not taken care of by expr conversion because there might
377 // not be a cast available for the store to convert the incoming value of.
378 // This code is basically here to make sure that pointers don't have casts
381 if (CastInst *CI = dyn_cast<CastInst>(Pointer))
382 if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
383 if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
384 // convertable types?
385 if (Val->getType()->isLosslesslyConvertableTo(CSPT->getElementType()) &&
386 !SI->hasIndices()) { // No subscripts yet!
387 PRINT_PEEPHOLE3("st-src-cast:in ", Pointer, Val, SI);
389 // Insert the new T cast instruction... stealing old T's name
390 CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
393 BI = BB->getInstList().insert(BI, NCI)+1;
395 // Replace the old store with a new one!
396 ReplaceInstWithInst(BB->getInstList(), BI,
397 SI = new StoreInst(NCI, CastSrc));
398 PRINT_PEEPHOLE3("st-src-cast:out", NCI, CastSrc, SI);
402 } else if (I->getOpcode() == Instruction::Add &&
403 isa<CastInst>(I->getOperand(1))) {
405 if (PeepholeOptimizeAddCast(BB, BI, I->getOperand(0),
406 cast<CastInst>(I->getOperand(1))))
418 static bool DoRaisePass(Function *F) {
419 bool Changed = false;
420 for (Function::iterator MI = F->begin(), ME = F->end(); MI != ME; ++MI) {
421 BasicBlock *BB = *MI;
422 BasicBlock::InstListType &BIL = BB->getInstList();
424 for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
425 #if DEBUG_PEEPHOLE_INSTS
426 cerr << "Processing: " << *BI;
428 if (dceInstruction(BIL, BI) || doConstantPropogation(BB, BI)) {
430 #ifdef DEBUG_PEEPHOLE_INSTS
431 cerr << "***\t\t^^-- DeadCode Elinated!\n";
433 } else if (PeepholeOptimize(BB, BI))
443 // RaisePointerReferences::doit - Raise a function representation to a higher
446 static bool doRPR(Function *F) {
447 #ifdef DEBUG_PEEPHOLE_INSTS
448 cerr << "\n\n\nStarting to work on Function '" << F->getName() << "'\n";
451 // Insert casts for all incoming pointer pointer values that are treated as
454 bool Changed = false, LocalChange;
457 #ifdef DEBUG_PEEPHOLE_INSTS
458 cerr << "Looping: \n" << F;
461 // Iterate over the function, refining it, until it converges on a stable
464 while (DoRaisePass(F)) LocalChange = true;
465 Changed |= LocalChange;
467 } while (LocalChange);
473 struct RaisePointerReferences : public FunctionPass {
474 virtual bool runOnFunction(Function *F) { return doRPR(F); }
478 Pass *createRaisePointerReferencesPass() {
479 return new RaisePointerReferences();