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/Method.h"
12 #include "llvm/iOther.h"
13 #include "llvm/iMemory.h"
14 #include "llvm/ConstantVals.h"
15 #include "llvm/Pass.h"
16 #include "llvm/Transforms/Scalar/DCE.h"
17 #include "llvm/Transforms/Scalar/ConstantHandling.h"
18 #include "llvm/Transforms/Scalar/ConstantProp.h"
19 #include "llvm/Analysis/Expressions.h"
20 #include "Support/STLExtras.h"
23 #include "llvm/Assembly/Writer.h"
25 //#define DEBUG_PEEPHOLE_INSTS 1
27 #ifdef DEBUG_PEEPHOLE_INSTS
28 #define PRINT_PEEPHOLE(ID, NUM, I) \
29 cerr << "Inst P/H " << ID << "[" << NUM << "] " << I;
31 #define PRINT_PEEPHOLE(ID, NUM, I)
34 #define PRINT_PEEPHOLE1(ID, I1) do { PRINT_PEEPHOLE(ID, 0, I1); } while (0)
35 #define PRINT_PEEPHOLE2(ID, I1, I2) \
36 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); } while (0)
37 #define PRINT_PEEPHOLE3(ID, I1, I2, I3) \
38 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
39 PRINT_PEEPHOLE(ID, 2, I3); } while (0)
40 #define PRINT_PEEPHOLE4(ID, I1, I2, I3, I4) \
41 do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
42 PRINT_PEEPHOLE(ID, 2, I3); PRINT_PEEPHOLE(ID, 3, I4); } while (0)
45 // isReinterpretingCast - Return true if the cast instruction specified will
46 // cause the operand to be "reinterpreted". A value is reinterpreted if the
47 // cast instruction would cause the underlying bits to change.
49 static inline bool isReinterpretingCast(const CastInst *CI) {
50 return!CI->getOperand(0)->getType()->isLosslesslyConvertableTo(CI->getType());
55 // Peephole optimize the following instructions:
56 // %t1 = cast ? to x *
57 // %t2 = add x * %SP, %t1 ;; Constant must be 2nd operand
59 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
60 // %t2 = cast <eltype> * %t3 to {<...>}*
62 static bool HandleCastToPointer(BasicBlock::iterator BI,
63 const PointerType *DestPTy) {
64 CastInst *CI = cast<CastInst>(*BI);
66 // Scan all of the uses, looking for any uses that are not add
67 // instructions. If we have non-adds, do not make this transformation.
69 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
71 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
72 if (BO->getOpcode() != Instruction::Add)
79 std::vector<Value*> Indices;
80 Value *Src = CI->getOperand(0);
81 const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
82 if (Result == 0) return false; // Not convertable...
84 PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);
86 // If we have a getelementptr capability... transform all of the
87 // add instruction uses into getelementptr's.
88 for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
90 Instruction *I = cast<Instruction>(*UI);
91 assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
92 "Use is not a valid add instruction!");
94 // Get the value added to the cast result pointer...
95 Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);
97 BasicBlock *BB = I->getParent();
98 BasicBlock::iterator AddIt = find(BB->getInstList().begin(),
99 BB->getInstList().end(), I);
101 GetElementPtrInst *GEP = new GetElementPtrInst(OtherPtr, Indices);
103 PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
105 // Replace the old add instruction with the shiny new GEP inst
106 ReplaceInstWithInst(BB->getInstList(), AddIt, GEP);
107 PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
112 // Peephole optimize the following instructions:
113 // %t1 = cast ulong <const int> to {<...>} *
114 // %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
117 // %t1 = cast {<...>}* %SP to int*
118 // %t5 = cast ulong <const int> to int*
119 // %t2 = add int* %t1, %t5 ;; int is same size as field
121 // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
122 // %t2 = cast <eltype> * %t3 to {<...>}*
124 static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
125 Value *AddOp1, CastInst *AddOp2) {
126 const CompositeType *CompTy;
127 Value *OffsetVal = AddOp2->getOperand(0);
128 Value *SrcPtr; // Of type pointer to struct...
130 if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
131 SrcPtr = AddOp1; // Handle the first case...
132 } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
133 SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
134 CompTy = getPointedToComposite(SrcPtr->getType());
137 // Only proceed if we have detected all of our conditions successfully...
138 if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
141 std::vector<Value*> Indices;
142 if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
143 return false; // Not convertable... perhaps next time
145 if (getPointedToComposite(AddOp1->getType())) { // case 1
146 PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
148 PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
151 GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
153 BI = BB->getInstList().insert(BI, GEP)+1;
155 Instruction *NCI = new CastInst(GEP, AddOp1->getType());
156 ReplaceInstWithInst(BB->getInstList(), BI, NCI);
157 PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
161 static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
162 Instruction *I = *BI;
164 if (CastInst *CI = dyn_cast<CastInst>(I)) {
165 Value *Src = CI->getOperand(0);
166 Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
167 const Type *DestTy = CI->getType();
169 // Peephole optimize the following instruction:
170 // %V2 = cast <ty> %V to <ty>
174 if (DestTy == Src->getType()) { // Check for a cast to same type as src!!
175 PRINT_PEEPHOLE1("cast-of-self-ty", CI);
176 CI->replaceAllUsesWith(Src);
177 if (!Src->hasName() && CI->hasName()) {
178 std::string Name = CI->getName();
180 Src->setName(Name, BB->getParent()->getSymbolTable());
185 // Peephole optimize the following instructions:
186 // %tmp = cast <ty> %V to <ty2>
187 // %V = cast <ty2> %tmp to <ty3> ; Where ty & ty2 are same size
189 // Into: cast <ty> %V to <ty3>
192 if (CastInst *CSrc = dyn_cast<CastInst>(SrcI))
193 if (isReinterpretingCast(CI) + isReinterpretingCast(CSrc) < 2) {
194 // We can only do c-c elimination if, at most, one cast does a
195 // reinterpretation of the input data.
197 // If legal, make this cast refer the the original casts argument!
199 PRINT_PEEPHOLE2("cast-cast:in ", CI, CSrc);
200 CI->setOperand(0, CSrc->getOperand(0));
201 PRINT_PEEPHOLE1("cast-cast:out", CI);
205 // Check to see if it's a cast of an instruction that does not depend on the
206 // specific type of the operands to do it's job.
207 if (!isReinterpretingCast(CI)) {
208 ValueTypeCache ConvertedTypes;
210 // Check to see if we can convert the users of the cast value to match the
211 // source type of the cast...
213 ConvertedTypes[CI] = CI->getType(); // Make sure the cast doesn't change
214 if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
215 PRINT_PEEPHOLE3("CAST-SRC-EXPR-CONV:in ", Src, CI, BB->getParent());
217 #ifdef DEBUG_PEEPHOLE_INSTS
218 cerr << "\nCONVERTING SRC EXPR TYPE:\n";
220 ValueMapCache ValueMap;
221 Value *E = ConvertExpressionToType(Src, DestTy, ValueMap);
222 if (Constant *CPV = dyn_cast<Constant>(E))
223 CI->replaceAllUsesWith(CPV);
225 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
226 PRINT_PEEPHOLE1("CAST-SRC-EXPR-CONV:out", E);
227 #ifdef DEBUG_PEEPHOLE_INSTS
228 cerr << "DONE CONVERTING SRC EXPR TYPE: \n" << BB->getParent();
233 // Check to see if we can convert the source of the cast to match the
234 // destination type of the cast...
236 ConvertedTypes.clear();
237 if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
238 PRINT_PEEPHOLE3("CAST-DEST-EXPR-CONV:in ", Src, CI, BB->getParent());
240 #ifdef DEBUG_PEEPHOLE_INSTS
241 cerr << "\nCONVERTING EXPR TYPE:\n";
243 ValueMapCache ValueMap;
244 ConvertValueToNewType(CI, Src, ValueMap); // This will delete CI!
246 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
247 PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
248 #ifdef DEBUG_PEEPHOLE_INSTS
249 cerr << "DONE CONVERTING EXPR TYPE: \n\n" << BB->getParent();
255 // Otherwise find out it this cast is a cast to a pointer type, which is
256 // then added to some other pointer, then loaded or stored through. If
257 // so, convert the add into a getelementptr instruction...
259 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
260 if (HandleCastToPointer(BI, DestPTy)) {
261 BI = BB->begin(); // Rescan basic block. BI might be invalidated.
266 // Check to see if we are casting from a structure pointer to a pointer to
267 // the first element of the structure... to avoid munching other peepholes,
268 // we only let this happen if there are no add uses of the cast.
270 // Peephole optimize the following instructions:
271 // %t1 = cast {<...>} * %StructPtr to <ty> *
273 // Into: %t2 = getelementptr {<...>} * %StructPtr, <0, 0, 0, ...>
274 // %t1 = cast <eltype> * %t1 to <ty> *
277 if (const CompositeType *CTy = getPointedToComposite(Src->getType()))
278 if (const PointerType *DestPTy = dyn_cast<PointerType>(DestTy)) {
280 // Loop over uses of the cast, checking for add instructions. If an add
281 // exists, this is probably a part of a more complex GEP, so we don't
282 // want to mess around with the cast.
284 bool HasAddUse = false;
285 for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
287 if (isa<Instruction>(*I) &&
288 cast<Instruction>(*I)->getOpcode() == Instruction::Add) {
289 HasAddUse = true; break;
292 // If it doesn't have an add use, check to see if the dest type is
293 // losslessly convertable to one of the types in the start of the struct
297 const Type *DestPointedTy = DestPTy->getElementType();
299 const CompositeType *CurCTy = CTy;
300 const Type *ElTy = 0;
302 // Build the index vector, full of all zeros
303 std::vector<Value*> Indices;
304 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
305 while (CurCTy && !isa<PointerType>(CurCTy)) {
306 if (const StructType *CurSTy = dyn_cast<StructType>(CurCTy)) {
307 // Check for a zero element struct type... if we have one, bail.
308 if (CurSTy->getElementTypes().size() == 0) break;
310 // Grab the first element of the struct type, which must lie at
311 // offset zero in the struct.
313 ElTy = CurSTy->getElementTypes()[0];
315 ElTy = cast<ArrayType>(CurCTy)->getElementType();
318 // Insert a zero to index through this type...
319 Indices.push_back(ConstantUInt::get(CurCTy->getIndexType(), 0));
321 // Did we find what we're looking for?
322 if (ElTy->isLosslesslyConvertableTo(DestPointedTy)) break;
324 // Nope, go a level deeper.
326 CurCTy = dyn_cast<CompositeType>(ElTy);
330 // Did we find what we were looking for? If so, do the transformation
332 PRINT_PEEPHOLE1("cast-for-first:in", CI);
334 // Insert the new T cast instruction... stealing old T's name
335 GetElementPtrInst *GEP = new GetElementPtrInst(Src, Indices,
338 BI = BB->getInstList().insert(BI, GEP)+1;
340 // Make the old cast instruction reference the new GEP instead of
341 // the old src value.
343 CI->setOperand(0, GEP);
345 PRINT_PEEPHOLE2("cast-for-first:out", GEP, CI);
353 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
354 Value *Val = SI->getOperand(0);
355 Value *Pointer = SI->getPointerOperand();
357 // Peephole optimize the following instructions:
358 // %t = cast <T1>* %P to <T2> * ;; If T1 is losslessly convertable to T2
359 // store <T2> %V, <T2>* %t
362 // %t = cast <T2> %V to <T1>
363 // store <T1> %t2, <T1>* %P
365 // Note: This is not taken care of by expr conversion because there might
366 // not be a cast available for the store to convert the incoming value of.
367 // This code is basically here to make sure that pointers don't have casts
370 if (CastInst *CI = dyn_cast<CastInst>(Pointer))
371 if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
372 if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
373 // convertable types?
374 if (Val->getType()->isLosslesslyConvertableTo(CSPT->getElementType()) &&
375 !SI->hasIndices()) { // No subscripts yet!
376 PRINT_PEEPHOLE3("st-src-cast:in ", Pointer, Val, SI);
378 // Insert the new T cast instruction... stealing old T's name
379 CastInst *NCI = new CastInst(Val, CSPT->getElementType(),
382 BI = BB->getInstList().insert(BI, NCI)+1;
384 // Replace the old store with a new one!
385 ReplaceInstWithInst(BB->getInstList(), BI,
386 SI = new StoreInst(NCI, CastSrc));
387 PRINT_PEEPHOLE3("st-src-cast:out", NCI, CastSrc, SI);
391 } else if (I->getOpcode() == Instruction::Add &&
392 isa<CastInst>(I->getOperand(1))) {
394 if (PeepholeOptimizeAddCast(BB, BI, I->getOperand(0),
395 cast<CastInst>(I->getOperand(1))))
407 static bool DoRaisePass(Method *M) {
408 bool Changed = false;
409 for (Method::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI) {
410 BasicBlock *BB = *MI;
411 BasicBlock::InstListType &BIL = BB->getInstList();
413 for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
414 #if DEBUG_PEEPHOLE_INSTS
415 cerr << "Processing: " << *BI;
417 if (dceInstruction(BIL, BI) || doConstantPropogation(BB, BI)) {
419 #ifdef DEBUG_PEEPHOLE_INSTS
420 cerr << "DeadCode Elinated!\n";
422 } else if (PeepholeOptimize(BB, BI))
432 // RaisePointerReferences::doit - Raise a method representation to a higher
435 static bool doRPR(Method *M) {
436 #ifdef DEBUG_PEEPHOLE_INSTS
437 cerr << "\n\n\nStarting to work on Method '" << M->getName() << "'\n";
440 // Insert casts for all incoming pointer pointer values that are treated as
443 bool Changed = false, LocalChange;
446 #ifdef DEBUG_PEEPHOLE_INSTS
447 cerr << "Looping: \n" << M;
450 // Iterate over the method, refining it, until it converges on a stable
453 while (DoRaisePass(M)) LocalChange = true;
454 Changed |= LocalChange;
456 } while (LocalChange);
462 struct RaisePointerReferences : public MethodPass {
463 virtual bool runOnMethod(Method *M) { return doRPR(M); }
467 Pass *createRaisePointerReferencesPass() {
468 return new RaisePointerReferences();