1 //===-- ConstantFolding.cpp - Analyze constant folding possibilities ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This family of functions determines the possibility of performing constant
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Analysis/ConstantFolding.h"
16 #include "llvm/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Function.h"
19 #include "llvm/GlobalVariable.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/Intrinsics.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/ADT/StringMap.h"
24 #include "llvm/Target/TargetData.h"
25 #include "llvm/Support/GetElementPtrTypeIterator.h"
26 #include "llvm/Support/MathExtras.h"
31 //===----------------------------------------------------------------------===//
32 // Constant Folding internal helper functions
33 //===----------------------------------------------------------------------===//
35 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
36 /// from a global, return the global and the constant. Because of
37 /// constantexprs, this function is recursive.
38 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
39 int64_t &Offset, const TargetData &TD) {
40 // Trivial case, constant is the global.
41 if ((GV = dyn_cast<GlobalValue>(C))) {
46 // Otherwise, if this isn't a constant expr, bail out.
47 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
48 if (!CE) return false;
50 // Look through ptr->int and ptr->ptr casts.
51 if (CE->getOpcode() == Instruction::PtrToInt ||
52 CE->getOpcode() == Instruction::BitCast)
53 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
55 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
56 if (CE->getOpcode() == Instruction::GetElementPtr) {
57 // Cannot compute this if the element type of the pointer is missing size
59 if (!cast<PointerType>(CE->getOperand(0)->getType())
60 ->getElementType()->isSized())
63 // If the base isn't a global+constant, we aren't either.
64 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
67 // Otherwise, add any offset that our operands provide.
68 gep_type_iterator GTI = gep_type_begin(CE);
69 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
71 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
72 if (!CI) return false; // Index isn't a simple constant?
73 if (CI->getZExtValue() == 0) continue; // Not adding anything.
75 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
77 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
79 const SequentialType *SQT = cast<SequentialType>(*GTI);
80 Offset += TD.getTypePaddedSize(SQT->getElementType())*CI->getSExtValue();
90 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
91 /// Attempt to symbolically evaluate the result of a binary operator merging
92 /// these together. If target data info is available, it is provided as TD,
93 /// otherwise TD is null.
94 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
95 Constant *Op1, const TargetData *TD){
98 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
99 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
103 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
104 // constant. This happens frequently when iterating over a global array.
105 if (Opc == Instruction::Sub && TD) {
106 GlobalValue *GV1, *GV2;
107 int64_t Offs1, Offs2;
109 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
110 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
112 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
113 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
120 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
121 /// constant expression, do so.
122 static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
123 const Type *ResultTy,
124 const TargetData *TD) {
125 Constant *Ptr = Ops[0];
126 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
129 uint64_t BasePtr = 0;
130 if (!Ptr->isNullValue()) {
131 // If this is a inttoptr from a constant int, we can fold this as the base,
132 // otherwise we can't.
133 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
134 if (CE->getOpcode() == Instruction::IntToPtr)
135 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
136 BasePtr = Base->getZExtValue();
142 // If this is a constant expr gep that is effectively computing an
143 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
144 for (unsigned i = 1; i != NumOps; ++i)
145 if (!isa<ConstantInt>(Ops[i]))
148 uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
149 (Value**)Ops+1, NumOps-1);
150 Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset+BasePtr);
151 return ConstantExpr::getIntToPtr(C, ResultTy);
154 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
155 /// targetdata. Return 0 if unfoldable.
156 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
157 const TargetData &TD) {
158 // If this is a bitcast from constant vector -> vector, fold it.
159 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
160 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
161 // If the element types match, VMCore can fold it.
162 unsigned NumDstElt = DestVTy->getNumElements();
163 unsigned NumSrcElt = CV->getNumOperands();
164 if (NumDstElt == NumSrcElt)
167 const Type *SrcEltTy = CV->getType()->getElementType();
168 const Type *DstEltTy = DestVTy->getElementType();
170 // Otherwise, we're changing the number of elements in a vector, which
171 // requires endianness information to do the right thing. For example,
172 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
173 // folds to (little endian):
174 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
175 // and to (big endian):
176 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
178 // First thing is first. We only want to think about integer here, so if
179 // we have something in FP form, recast it as integer.
180 if (DstEltTy->isFloatingPoint()) {
181 // Fold to an vector of integers with same size as our FP type.
182 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
183 const Type *DestIVTy = VectorType::get(IntegerType::get(FPWidth),
185 // Recursively handle this integer conversion, if possible.
186 C = FoldBitCast(C, DestIVTy, TD);
189 // Finally, VMCore can handle this now that #elts line up.
190 return ConstantExpr::getBitCast(C, DestTy);
193 // Okay, we know the destination is integer, if the input is FP, convert
194 // it to integer first.
195 if (SrcEltTy->isFloatingPoint()) {
196 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
197 const Type *SrcIVTy = VectorType::get(IntegerType::get(FPWidth),
199 // Ask VMCore to do the conversion now that #elts line up.
200 C = ConstantExpr::getBitCast(C, SrcIVTy);
201 CV = dyn_cast<ConstantVector>(C);
202 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
205 // Now we know that the input and output vectors are both integer vectors
206 // of the same size, and that their #elements is not the same. Do the
207 // conversion here, which depends on whether the input or output has
209 bool isLittleEndian = TD.isLittleEndian();
211 SmallVector<Constant*, 32> Result;
212 if (NumDstElt < NumSrcElt) {
213 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
214 Constant *Zero = Constant::getNullValue(DstEltTy);
215 unsigned Ratio = NumSrcElt/NumDstElt;
216 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
218 for (unsigned i = 0; i != NumDstElt; ++i) {
219 // Build each element of the result.
220 Constant *Elt = Zero;
221 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
222 for (unsigned j = 0; j != Ratio; ++j) {
223 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
224 if (!Src) return 0; // Reject constantexpr elements.
226 // Zero extend the element to the right size.
227 Src = ConstantExpr::getZExt(Src, Elt->getType());
229 // Shift it to the right place, depending on endianness.
230 Src = ConstantExpr::getShl(Src,
231 ConstantInt::get(Src->getType(), ShiftAmt));
232 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
235 Elt = ConstantExpr::getOr(Elt, Src);
237 Result.push_back(Elt);
240 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
241 unsigned Ratio = NumDstElt/NumSrcElt;
242 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
244 // Loop over each source value, expanding into multiple results.
245 for (unsigned i = 0; i != NumSrcElt; ++i) {
246 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
247 if (!Src) return 0; // Reject constantexpr elements.
249 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
250 for (unsigned j = 0; j != Ratio; ++j) {
251 // Shift the piece of the value into the right place, depending on
253 Constant *Elt = ConstantExpr::getLShr(Src,
254 ConstantInt::get(Src->getType(), ShiftAmt));
255 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
257 // Truncate and remember this piece.
258 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
263 return ConstantVector::get(&Result[0], Result.size());
271 //===----------------------------------------------------------------------===//
272 // Constant Folding public APIs
273 //===----------------------------------------------------------------------===//
276 /// ConstantFoldInstruction - Attempt to constant fold the specified
277 /// instruction. If successful, the constant result is returned, if not, null
278 /// is returned. Note that this function can only fail when attempting to fold
279 /// instructions like loads and stores, which have no constant expression form.
281 Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
282 if (PHINode *PN = dyn_cast<PHINode>(I)) {
283 if (PN->getNumIncomingValues() == 0)
284 return UndefValue::get(PN->getType());
286 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
287 if (Result == 0) return 0;
289 // Handle PHI nodes specially here...
290 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
291 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
292 return 0; // Not all the same incoming constants...
294 // If we reach here, all incoming values are the same constant.
298 // Scan the operand list, checking to see if they are all constants, if so,
299 // hand off to ConstantFoldInstOperands.
300 SmallVector<Constant*, 8> Ops;
301 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
302 if (Constant *Op = dyn_cast<Constant>(*i))
305 return 0; // All operands not constant!
307 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
308 return ConstantFoldCompareInstOperands(CI->getPredicate(),
309 &Ops[0], Ops.size(), TD);
311 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
312 &Ops[0], Ops.size(), TD);
315 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
316 /// using the specified TargetData. If successful, the constant result is
317 /// result is returned, if not, null is returned.
318 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
319 const TargetData *TD) {
320 assert(TD && "ConstantFoldConstantExpression requires a valid TargetData.");
322 SmallVector<Constant*, 8> Ops;
323 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
324 Ops.push_back(cast<Constant>(*i));
327 return ConstantFoldCompareInstOperands(CE->getPredicate(),
328 &Ops[0], Ops.size(), TD);
330 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
331 &Ops[0], Ops.size(), TD);
334 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
335 /// specified opcode and operands. If successful, the constant result is
336 /// returned, if not, null is returned. Note that this function can fail when
337 /// attempting to fold instructions like loads and stores, which have no
338 /// constant expression form.
340 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
341 Constant* const* Ops, unsigned NumOps,
342 const TargetData *TD) {
343 // Handle easy binops first.
344 if (Instruction::isBinaryOp(Opcode)) {
345 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
346 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
349 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
354 case Instruction::Call:
355 if (Function *F = dyn_cast<Function>(Ops[0]))
356 if (canConstantFoldCallTo(F))
357 return ConstantFoldCall(F, Ops+1, NumOps-1);
359 case Instruction::ICmp:
360 case Instruction::FCmp:
361 case Instruction::VICmp:
362 case Instruction::VFCmp:
363 assert(0 &&"This function is invalid for compares: no predicate specified");
364 case Instruction::PtrToInt:
365 // If the input is a inttoptr, eliminate the pair. This requires knowing
366 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
367 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
368 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
369 Constant *Input = CE->getOperand(0);
370 unsigned InWidth = Input->getType()->getPrimitiveSizeInBits();
371 if (TD->getPointerSizeInBits() < InWidth) {
373 ConstantInt::get(APInt::getLowBitsSet(InWidth,
374 TD->getPointerSizeInBits()));
375 Input = ConstantExpr::getAnd(Input, Mask);
377 // Do a zext or trunc to get to the dest size.
378 return ConstantExpr::getIntegerCast(Input, DestTy, false);
381 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
382 case Instruction::IntToPtr:
383 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
384 // the int size is >= the ptr size. This requires knowing the width of a
385 // pointer, so it can't be done in ConstantExpr::getCast.
386 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
388 TD->getPointerSizeInBits() <=
389 CE->getType()->getPrimitiveSizeInBits()) {
390 if (CE->getOpcode() == Instruction::PtrToInt) {
391 Constant *Input = CE->getOperand(0);
392 Constant *C = FoldBitCast(Input, DestTy, *TD);
393 return C ? C : ConstantExpr::getBitCast(Input, DestTy);
395 // If there's a constant offset added to the integer value before
396 // it is casted back to a pointer, see if the expression can be
397 // converted into a GEP.
398 if (CE->getOpcode() == Instruction::Add)
399 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
400 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
401 if (R->getOpcode() == Instruction::PtrToInt)
402 if (GlobalVariable *GV =
403 dyn_cast<GlobalVariable>(R->getOperand(0))) {
404 const PointerType *GVTy = cast<PointerType>(GV->getType());
405 if (const ArrayType *AT =
406 dyn_cast<ArrayType>(GVTy->getElementType())) {
407 const Type *ElTy = AT->getElementType();
408 uint64_t PaddedSize = TD->getTypePaddedSize(ElTy);
409 APInt PSA(L->getValue().getBitWidth(), PaddedSize);
410 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
411 L->getValue().urem(PSA) == 0) {
412 APInt ElemIdx = L->getValue().udiv(PSA);
413 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
414 AT->getNumElements()))) {
415 Constant *Index[] = {
416 Constant::getNullValue(CE->getType()),
417 ConstantInt::get(ElemIdx)
419 return ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
426 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
427 case Instruction::Trunc:
428 case Instruction::ZExt:
429 case Instruction::SExt:
430 case Instruction::FPTrunc:
431 case Instruction::FPExt:
432 case Instruction::UIToFP:
433 case Instruction::SIToFP:
434 case Instruction::FPToUI:
435 case Instruction::FPToSI:
436 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
437 case Instruction::BitCast:
439 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD))
441 return ConstantExpr::getBitCast(Ops[0], DestTy);
442 case Instruction::Select:
443 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
444 case Instruction::ExtractElement:
445 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
446 case Instruction::InsertElement:
447 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
448 case Instruction::ShuffleVector:
449 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
450 case Instruction::GetElementPtr:
451 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
454 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
458 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
459 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
460 /// returns a constant expression of the specified operands.
462 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
463 Constant*const * Ops,
465 const TargetData *TD) {
466 // fold: icmp (inttoptr x), null -> icmp x, 0
467 // fold: icmp (ptrtoint x), 0 -> icmp x, null
468 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
469 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
471 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
472 // around to know if bit truncation is happening.
473 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
474 if (TD && Ops[1]->isNullValue()) {
475 const Type *IntPtrTy = TD->getIntPtrType();
476 if (CE0->getOpcode() == Instruction::IntToPtr) {
477 // Convert the integer value to the right size to ensure we get the
478 // proper extension or truncation.
479 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
481 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
482 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
485 // Only do this transformation if the int is intptrty in size, otherwise
486 // there is a truncation or extension that we aren't modeling.
487 if (CE0->getOpcode() == Instruction::PtrToInt &&
488 CE0->getType() == IntPtrTy) {
489 Constant *C = CE0->getOperand(0);
490 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
492 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
496 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
497 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
498 const Type *IntPtrTy = TD->getIntPtrType();
500 if (CE0->getOpcode() == Instruction::IntToPtr) {
501 // Convert the integer value to the right size to ensure we get the
502 // proper extension or truncation.
503 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
505 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
507 Constant *NewOps[] = { C0, C1 };
508 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
511 // Only do this transformation if the int is intptrty in size, otherwise
512 // there is a truncation or extension that we aren't modeling.
513 if ((CE0->getOpcode() == Instruction::PtrToInt &&
514 CE0->getType() == IntPtrTy &&
515 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
516 Constant *NewOps[] = {
517 CE0->getOperand(0), CE1->getOperand(0)
519 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
524 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
528 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
529 /// getelementptr constantexpr, return the constant value being addressed by the
530 /// constant expression, or null if something is funny and we can't decide.
531 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
533 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
534 return 0; // Do not allow stepping over the value!
536 // Loop over all of the operands, tracking down which value we are
538 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
539 for (++I; I != E; ++I)
540 if (const StructType *STy = dyn_cast<StructType>(*I)) {
541 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
542 assert(CU->getZExtValue() < STy->getNumElements() &&
543 "Struct index out of range!");
544 unsigned El = (unsigned)CU->getZExtValue();
545 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
546 C = CS->getOperand(El);
547 } else if (isa<ConstantAggregateZero>(C)) {
548 C = Constant::getNullValue(STy->getElementType(El));
549 } else if (isa<UndefValue>(C)) {
550 C = UndefValue::get(STy->getElementType(El));
554 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
555 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
556 if (CI->getZExtValue() >= ATy->getNumElements())
558 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
559 C = CA->getOperand(CI->getZExtValue());
560 else if (isa<ConstantAggregateZero>(C))
561 C = Constant::getNullValue(ATy->getElementType());
562 else if (isa<UndefValue>(C))
563 C = UndefValue::get(ATy->getElementType());
566 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
567 if (CI->getZExtValue() >= PTy->getNumElements())
569 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
570 C = CP->getOperand(CI->getZExtValue());
571 else if (isa<ConstantAggregateZero>(C))
572 C = Constant::getNullValue(PTy->getElementType());
573 else if (isa<UndefValue>(C))
574 C = UndefValue::get(PTy->getElementType());
587 //===----------------------------------------------------------------------===//
588 // Constant Folding for Calls
591 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
592 /// the specified function.
594 llvm::canConstantFoldCallTo(const Function *F) {
595 switch (F->getIntrinsicID()) {
596 case Intrinsic::sqrt:
597 case Intrinsic::powi:
598 case Intrinsic::bswap:
599 case Intrinsic::ctpop:
600 case Intrinsic::ctlz:
601 case Intrinsic::cttz:
606 if (!F->hasName()) return false;
607 const char *Str = F->getNameStart();
608 unsigned Len = F->getNameLen();
610 // In these cases, the check of the length is required. We don't want to
611 // return true for a name like "cos\0blah" which strcmp would return equal to
612 // "cos", but has length 8.
614 default: return false;
617 return !strcmp(Str, "acos") || !strcmp(Str, "asin") ||
618 !strcmp(Str, "atan");
620 return !strcmp(Str, "atan2");
624 return !strcmp(Str, "cos");
626 return !strcmp(Str, "ceil") || !strcmp(Str, "cosf") ||
627 !strcmp(Str, "cosh");
631 return !strcmp(Str, "exp");
635 return !strcmp(Str, "fabs") || !strcmp(Str, "fmod");
637 return !strcmp(Str, "floor");
641 if (Len == 3 && !strcmp(Str, "log"))
643 if (Len == 5 && !strcmp(Str, "log10"))
647 if (Len == 3 && !strcmp(Str, "pow"))
652 return !strcmp(Str, "sin");
654 return !strcmp(Str, "sinh") || !strcmp(Str, "sqrt") ||
655 !strcmp(Str, "sinf");
657 return !strcmp(Str, "sqrtf");
660 if (Len == 3 && !strcmp(Str, "tan"))
662 else if (Len == 4 && !strcmp(Str, "tanh"))
668 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
677 if (Ty == Type::FloatTy)
678 return ConstantFP::get(APFloat((float)V));
679 if (Ty == Type::DoubleTy)
680 return ConstantFP::get(APFloat(V));
681 assert(0 && "Can only constant fold float/double");
682 return 0; // dummy return to suppress warning
685 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
695 if (Ty == Type::FloatTy)
696 return ConstantFP::get(APFloat((float)V));
697 if (Ty == Type::DoubleTy)
698 return ConstantFP::get(APFloat(V));
699 assert(0 && "Can only constant fold float/double");
700 return 0; // dummy return to suppress warning
703 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
704 /// with the specified arguments, returning null if unsuccessful.
707 llvm::ConstantFoldCall(Function *F,
708 Constant* const* Operands, unsigned NumOperands) {
709 if (!F->hasName()) return 0;
710 const char *Str = F->getNameStart();
711 unsigned Len = F->getNameLen();
713 const Type *Ty = F->getReturnType();
714 if (NumOperands == 1) {
715 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
716 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
718 /// Currently APFloat versions of these functions do not exist, so we use
719 /// the host native double versions. Float versions are not called
720 /// directly but for all these it is true (float)(f((double)arg)) ==
721 /// f(arg). Long double not supported yet.
722 double V = Ty==Type::FloatTy ? (double)Op->getValueAPF().convertToFloat():
723 Op->getValueAPF().convertToDouble();
726 if (Len == 4 && !strcmp(Str, "acos"))
727 return ConstantFoldFP(acos, V, Ty);
728 else if (Len == 4 && !strcmp(Str, "asin"))
729 return ConstantFoldFP(asin, V, Ty);
730 else if (Len == 4 && !strcmp(Str, "atan"))
731 return ConstantFoldFP(atan, V, Ty);
734 if (Len == 4 && !strcmp(Str, "ceil"))
735 return ConstantFoldFP(ceil, V, Ty);
736 else if (Len == 3 && !strcmp(Str, "cos"))
737 return ConstantFoldFP(cos, V, Ty);
738 else if (Len == 4 && !strcmp(Str, "cosh"))
739 return ConstantFoldFP(cosh, V, Ty);
740 else if (Len == 4 && !strcmp(Str, "cosf"))
741 return ConstantFoldFP(cos, V, Ty);
744 if (Len == 3 && !strcmp(Str, "exp"))
745 return ConstantFoldFP(exp, V, Ty);
748 if (Len == 4 && !strcmp(Str, "fabs"))
749 return ConstantFoldFP(fabs, V, Ty);
750 else if (Len == 5 && !strcmp(Str, "floor"))
751 return ConstantFoldFP(floor, V, Ty);
754 if (Len == 3 && !strcmp(Str, "log") && V > 0)
755 return ConstantFoldFP(log, V, Ty);
756 else if (Len == 5 && !strcmp(Str, "log10") && V > 0)
757 return ConstantFoldFP(log10, V, Ty);
758 else if (!strcmp(Str, "llvm.sqrt.f32") ||
759 !strcmp(Str, "llvm.sqrt.f64")) {
761 return ConstantFoldFP(sqrt, V, Ty);
763 return Constant::getNullValue(Ty);
767 if (Len == 3 && !strcmp(Str, "sin"))
768 return ConstantFoldFP(sin, V, Ty);
769 else if (Len == 4 && !strcmp(Str, "sinh"))
770 return ConstantFoldFP(sinh, V, Ty);
771 else if (Len == 4 && !strcmp(Str, "sqrt") && V >= 0)
772 return ConstantFoldFP(sqrt, V, Ty);
773 else if (Len == 5 && !strcmp(Str, "sqrtf") && V >= 0)
774 return ConstantFoldFP(sqrt, V, Ty);
775 else if (Len == 4 && !strcmp(Str, "sinf"))
776 return ConstantFoldFP(sin, V, Ty);
779 if (Len == 3 && !strcmp(Str, "tan"))
780 return ConstantFoldFP(tan, V, Ty);
781 else if (Len == 4 && !strcmp(Str, "tanh"))
782 return ConstantFoldFP(tanh, V, Ty);
787 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
788 if (Len > 11 && !memcmp(Str, "llvm.bswap", 10))
789 return ConstantInt::get(Op->getValue().byteSwap());
790 else if (Len > 11 && !memcmp(Str, "llvm.ctpop", 10))
791 return ConstantInt::get(Ty, Op->getValue().countPopulation());
792 else if (Len > 10 && !memcmp(Str, "llvm.cttz", 9))
793 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
794 else if (Len > 10 && !memcmp(Str, "llvm.ctlz", 9))
795 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
797 } else if (NumOperands == 2) {
798 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
799 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
801 double Op1V = Ty==Type::FloatTy ?
802 (double)Op1->getValueAPF().convertToFloat():
803 Op1->getValueAPF().convertToDouble();
804 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
805 double Op2V = Ty==Type::FloatTy ?
806 (double)Op2->getValueAPF().convertToFloat():
807 Op2->getValueAPF().convertToDouble();
809 if (Len == 3 && !strcmp(Str, "pow")) {
810 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
811 } else if (Len == 4 && !strcmp(Str, "fmod")) {
812 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
813 } else if (Len == 5 && !strcmp(Str, "atan2")) {
814 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
816 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
817 if (!strcmp(Str, "llvm.powi.f32")) {
818 return ConstantFP::get(APFloat((float)std::pow((float)Op1V,
819 (int)Op2C->getZExtValue())));
820 } else if (!strcmp(Str, "llvm.powi.f64")) {
821 return ConstantFP::get(APFloat((double)std::pow((double)Op1V,
822 (int)Op2C->getZExtValue())));