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/iOther.h"
12 #include "llvm/iMemory.h"
13 #include "llvm/Pass.h"
14 #include "llvm/ConstantHandling.h"
15 #include "llvm/Transforms/Scalar/DCE.h"
16 #include "llvm/Transforms/Scalar/ConstantProp.h"
17 #include "llvm/Analysis/Expressions.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());
51 // Peephole optimize the following instructions:
52 // %t1 = cast ? to x *
53 // %t2 = add x * %SP, %t1 ;; Constant must be 2nd operand
55 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
56 // %t2 = cast <eltype> * %t3 to {<...>}*
58 static bool HandleCastToPointer(BasicBlock::iterator BI,
59 const PointerType *DestPTy) {
60 CastInst *CI = cast<CastInst>(*BI);
61 if (CI->use_empty()) return false;
63 // Scan all of the uses, looking for any uses that are not add
64 // instructions. If we have non-adds, do not make this transformation.
66 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
68 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
69 if (BO->getOpcode() != Instruction::Add)
76 std::vector<Value*> Indices;
77 Value *Src = CI->getOperand(0);
78 const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
79 if (Result == 0) return false; // Not convertable...
81 PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);
83 // If we have a getelementptr capability... transform all of the
84 // add instruction uses into getelementptr's.
85 while (!CI->use_empty()) {
86 BinaryOperator *I = cast<BinaryOperator>(*CI->use_begin());
87 assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
88 "Use is not a valid add instruction!");
90 // Get the value added to the cast result pointer...
91 Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);
93 Instruction *GEP = new GetElementPtrInst(OtherPtr, Indices, I->getName());
94 PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
96 if (GEP->getType() == I->getType()) {
97 // Replace the old add instruction with the shiny new GEP inst
98 ReplaceInstWithInst(I, GEP);
100 // If the type produced by the gep instruction differs from the original
101 // add instruction type, insert a cast now.
104 // Insert the GEP instruction before the old add instruction... and get an
105 // iterator to point at the add instruction...
106 BasicBlock::iterator GEPI = InsertInstBeforeInst(GEP, I)+1;
108 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
109 CastInst *CI = new CastInst(GEP, I->getType());
112 // Replace the old add instruction with the shiny new GEP inst
113 ReplaceInstWithInst(I->getParent()->getInstList(), GEPI, GEP);
116 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
121 // Peephole optimize the following instructions:
122 // %t1 = cast ulong <const int> to {<...>} *
123 // %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
126 // %t1 = cast {<...>}* %SP to int*
127 // %t5 = cast ulong <const int> to int*
128 // %t2 = add int* %t1, %t5 ;; int is same size as field
130 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
131 // %t2 = cast <eltype> * %t3 to {<...>}*
133 static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
134 Value *AddOp1, CastInst *AddOp2) {
135 const CompositeType *CompTy;
136 Value *OffsetVal = AddOp2->getOperand(0);
137 Value *SrcPtr; // Of type pointer to struct...
139 if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
140 SrcPtr = AddOp1; // Handle the first case...
141 } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
142 SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
143 CompTy = getPointedToComposite(SrcPtr->getType());
146 // Only proceed if we have detected all of our conditions successfully...
147 if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
150 std::vector<Value*> Indices;
151 if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
152 return false; // Not convertable... perhaps next time
154 if (getPointedToComposite(AddOp1->getType())) { // case 1
155 PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
157 PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
160 GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
162 BI = BB->getInstList().insert(BI, GEP)+1;
164 Instruction *NCI = new CastInst(GEP, AddOp1->getType());
165 ReplaceInstWithInst(BB->getInstList(), BI, NCI);
166 PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
170 static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
171 Instruction *I = *BI;
173 if (CastInst *CI = dyn_cast<CastInst>(I)) {
174 Value *Src = CI->getOperand(0);
175 Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
176 const Type *DestTy = CI->getType();
178 // Peephole optimize the following instruction:
179 // %V2 = cast <ty> %V to <ty>
183 if (DestTy == Src->getType()) { // Check for a cast to same type as src!!
184 PRINT_PEEPHOLE1("cast-of-self-ty", CI);
185 CI->replaceAllUsesWith(Src);
186 if (!Src->hasName() && CI->hasName()) {
187 std::string Name = CI->getName();
189 Src->setName(Name, BB->getParent()->getSymbolTable());
194 // Peephole optimize the following instructions:
195 // %tmp = cast <ty> %V to <ty2>
196 // %V = cast <ty2> %tmp to <ty3> ; Where ty & ty2 are same size
198 // Into: cast <ty> %V to <ty3>
201 if (CastInst *CSrc = dyn_cast<CastInst>(SrcI))
202 if (isReinterpretingCast(CI) + isReinterpretingCast(CSrc) < 2) {
203 // We can only do c-c elimination if, at most, one cast does a
204 // reinterpretation of the input data.
206 // If legal, make this cast refer the the original casts argument!
208 PRINT_PEEPHOLE2("cast-cast:in ", CI, CSrc);
209 CI->setOperand(0, CSrc->getOperand(0));
210 PRINT_PEEPHOLE1("cast-cast:out", CI);
214 // Check to see if it's a cast of an instruction that does not depend on the
215 // specific type of the operands to do it's job.
216 if (!isReinterpretingCast(CI)) {
217 ValueTypeCache ConvertedTypes;
219 // Check to see if we can convert the users of the cast value to match the
220 // source type of the cast...
222 ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
223 if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
224 PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", Src, CI, BB->getParent());
226 #ifdef DEBUG_PEEPHOLE_INSTS
227 cerr << "\nCONVERTING SRC EXPR TYPE:\n";
229 ValueMapCache ValueMap;
230 Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
231 if (Constant *CPV = dyn_cast<Constant>(E))
232 CI->replaceAllUsesWith(CPV);
234 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
235 PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", E);
236 #ifdef DEBUG_PEEPHOLE_INSTS
237 cerr << "DONE CONVERTING SRC EXPR TYPE: \n" << BB->getParent();
242 // Check to see if we can convert the source of the cast to match the
243 // destination type of the cast...
245 ConvertedTypes.clear();
246 if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
247 PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", Src, CI, BB->getParent());
249 #ifdef DEBUG_PEEPHOLE_INSTS
250 cerr << "\nCONVERTING EXPR TYPE:\n";
252 ValueMapCache ValueMap;
253 ConvertValueToNewType(CI, Src, ValueMap); // This will delete CI!
255 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
256 PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
257 #ifdef DEBUG_PEEPHOLE_INSTS
258 cerr << "DONE CONVERTING EXPR TYPE: \n\n" << BB->getParent();
264 // Otherwise find out it this cast is a cast to a pointer type, which is
265 // then added to some other pointer, then loaded or stored through. If
266 // so, convert the add into a getelementptr instruction...
268 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
269 if (HandleCastToPointer(BI, DestPTy)) {
270 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
275 // Check to see if we are casting from a structure pointer to a pointer to
276 // the first element of the structure... to avoid munching other peepholes,
277 // we only let this happen if there are no add uses of the cast.
279 // Peephole optimize the following instructions:
280 // %t1 = cast {<...>} * %StructPtr to <ty> *
282 // Into: %t2 = getelementptr {<...>} * %StructPtr, <0, 0, 0, ...>
283 // %t1 = cast <eltype> * %t1 to <ty> *
286 if (const CompositeType *CTy = getPointedToComposite(Src->getType()))
287 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
289 // Loop over uses of the cast, checking for add instructions. If an add
290 // exists, this is probably a part of a more complex GEP, so we don't
291 // want to mess around with the cast.
293 bool HasAddUse = false;
294 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
296 if (isa<Instruction>(*I) &&
297 cast<Instruction>(*I)->getOpcode() == Instruction::Add) {
298 HasAddUse = true; break;
301 // If it doesn't have an add use, check to see if the dest type is
302 // losslessly convertable to one of the types in the start of the struct
306 const Type *DestPointedTy = DestPTy->getElementType();
308 const CompositeType *CurCTy = CTy;
309 const Type *ElTy = 0;
311 // Build the index vector, full of all zeros
312 std::vector<Value*> Indices;
313 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
314 while (CurCTy && !isa<PointerType>(CurCTy)) {
315 if (const StructType *CurSTy = dyn_cast<StructType>(CurCTy)) {
316 // Check for a zero element struct type... if we have one, bail.
317 if (CurSTy->getElementTypes().size() == 0) break;
319 // Grab the first element of the struct type, which must lie at
320 // offset zero in the struct.
322 ElTy = CurSTy->getElementTypes()[0];
324 ElTy = cast<ArrayType>(CurCTy)->getElementType();
327 // Insert a zero to index through this type...
328 Indices.push_back(ConstantUInt::get(CurCTy->getIndexType(), 0));
330 // Did we find what we're looking for?
331 if (ElTy->isLosslesslyConvertableTo(DestPointedTy)) break;
333 // Nope, go a level deeper.
335 CurCTy = dyn_cast<CompositeType>(ElTy);
339 // Did we find what we were looking for? If so, do the transformation
341 PRINT_PEEPHOLE1("cast-for-first:in", CI);
343 // Insert the new T cast instruction... stealing old T's name
344 GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
347 BI = BB->getInstList().insert(BI, GEP)+1;
349 // Make the old cast instruction reference the new GEP instead of
350 // the old src value.
352 CI->setOperand(0, GEP);
354 PRINT_PEEPHOLE2("cast-for-first:out", GEP, CI);
362 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
363 Value *Val = SI->getOperand(0);
364 Value *Pointer = SI->getPointerOperand();
366 // Peephole optimize the following instructions:
367 // %t = cast <T1>* %P to <T2> * ;; If T1 is losslessly convertable to T2
368 // store <T2> %V, <T2>* %t
371 // %t = cast <T2> %V to <T1>
372 // store <T1> %t2, <T1>* %P
374 // Note: This is not taken care of by expr conversion because there might
375 // not be a cast available for the store to convert the incoming value of.
376 // This code is basically here to make sure that pointers don't have casts
379 if (CastInst *CI = dyn_cast<CastInst>(Pointer))
380 if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
381 if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
382 // convertable types?
383 if (Val->getType()->isLosslesslyConvertableTo(CSPT->getElementType()) &&
384 !SI->hasIndices()) { // No subscripts yet!
385 PRINT_PEEPHOLE3("st-src-cast:in ", Pointer, Val, SI);
387 // Insert the new T cast instruction... stealing old T's name
388 CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
391 BI = BB->getInstList().insert(BI, NCI)+1;
393 // Replace the old store with a new one!
394 ReplaceInstWithInst(BB->getInstList(), BI,
395 SI = new StoreInst(NCI, CastSrc));
396 PRINT_PEEPHOLE3("st-src-cast:out", NCI, CastSrc, SI);
400 } else if (I->getOpcode() == Instruction::Add &&
401 isa<CastInst>(I->getOperand(1))) {
403 if (PeepholeOptimizeAddCast(BB, BI, I->getOperand(0),
404 cast<CastInst>(I->getOperand(1))))
416 static bool DoRaisePass(Function *F) {
417 bool Changed = false;
418 for (Function::iterator MI = F->begin(), ME = F->end(); MI != ME; ++MI) {
419 BasicBlock *BB = *MI;
420 BasicBlock::InstListType &BIL = BB->getInstList();
422 for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
423 #if DEBUG_PEEPHOLE_INSTS
424 cerr << "Processing: " << *BI;
426 if (dceInstruction(BIL, BI) || doConstantPropogation(BB, BI)) {
428 #ifdef DEBUG_PEEPHOLE_INSTS
429 cerr << "***\t\t^^-- DeadCode Elinated!\n";
431 } else if (PeepholeOptimize(BB, BI))
441 // RaisePointerReferences::doit - Raise a function representation to a higher
444 static bool doRPR(Function *F) {
445 #ifdef DEBUG_PEEPHOLE_INSTS
446 cerr << "\n\n\nStarting to work on Function '" << F->getName() << "'\n";
449 // Insert casts for all incoming pointer pointer values that are treated as
452 bool Changed = false, LocalChange;
455 #ifdef DEBUG_PEEPHOLE_INSTS
456 cerr << "Looping: \n" << F;
459 // Iterate over the function, refining it, until it converges on a stable
462 while (DoRaisePass(F)) LocalChange = true;
463 Changed |= LocalChange;
465 } while (LocalChange);
471 struct RaisePointerReferences : public FunctionPass {
472 const char *getPassName() const { return "Raise Pointer References"; }
474 virtual bool runOnFunction(Function *F) { return doRPR(F); }
476 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
482 Pass *createRaisePointerReferencesPass() {
483 return new RaisePointerReferences();