1 //===-- ConstantFolding.cpp - Fold instructions into constants ------------===//
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 file defines routines for folding instructions into constants.
12 // Also, to supplement the basic VMCore ConstantExpr simplifications,
13 // this file defines some additional folding routines that can make use of
14 // TargetData information. These functions cannot go in VMCore due to library
17 //===----------------------------------------------------------------------===//
19 #include "llvm/Analysis/ConstantFolding.h"
20 #include "llvm/Constants.h"
21 #include "llvm/DerivedTypes.h"
22 #include "llvm/Function.h"
23 #include "llvm/GlobalVariable.h"
24 #include "llvm/Instructions.h"
25 #include "llvm/Intrinsics.h"
26 #include "llvm/LLVMContext.h"
27 #include "llvm/Analysis/ValueTracking.h"
28 #include "llvm/Target/TargetData.h"
29 #include "llvm/ADT/SmallVector.h"
30 #include "llvm/ADT/StringMap.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/GetElementPtrTypeIterator.h"
33 #include "llvm/Support/MathExtras.h"
38 //===----------------------------------------------------------------------===//
39 // Constant Folding internal helper functions
40 //===----------------------------------------------------------------------===//
42 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
43 /// from a global, return the global and the constant. Because of
44 /// constantexprs, this function is recursive.
45 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
46 int64_t &Offset, const TargetData &TD) {
47 // Trivial case, constant is the global.
48 if ((GV = dyn_cast<GlobalValue>(C))) {
53 // Otherwise, if this isn't a constant expr, bail out.
54 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
55 if (!CE) return false;
57 // Look through ptr->int and ptr->ptr casts.
58 if (CE->getOpcode() == Instruction::PtrToInt ||
59 CE->getOpcode() == Instruction::BitCast)
60 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
62 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
63 if (CE->getOpcode() == Instruction::GetElementPtr) {
64 // Cannot compute this if the element type of the pointer is missing size
66 if (!cast<PointerType>(CE->getOperand(0)->getType())
67 ->getElementType()->isSized())
70 // If the base isn't a global+constant, we aren't either.
71 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
74 // Otherwise, add any offset that our operands provide.
75 gep_type_iterator GTI = gep_type_begin(CE);
76 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
78 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
79 if (!CI) return false; // Index isn't a simple constant?
80 if (CI->getZExtValue() == 0) continue; // Not adding anything.
82 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
84 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
86 const SequentialType *SQT = cast<SequentialType>(*GTI);
87 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue();
96 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
97 /// produce if it is constant and determinable. If this is not determinable,
99 Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C,
100 const TargetData *TD) {
101 // First, try the easy cases:
102 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
103 if (GV->isConstant() && GV->hasDefinitiveInitializer())
104 return GV->getInitializer();
106 // If the loaded value isn't a constant expr, we can't handle it.
107 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
110 if (CE->getOpcode() == Instruction::GetElementPtr) {
111 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
112 if (GV->isConstant() && GV->hasDefinitiveInitializer())
114 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
118 // Instead of loading constant c string, use corresponding integer value
119 // directly if string length is small enough.
121 if (TD && GetConstantStringInfo(CE->getOperand(0), Str) && !Str.empty()) {
122 unsigned len = Str.length();
123 const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
124 unsigned numBits = Ty->getPrimitiveSizeInBits();
125 // Replace LI with immediate integer store.
126 if ((numBits >> 3) == len + 1) {
127 APInt StrVal(numBits, 0);
128 APInt SingleChar(numBits, 0);
129 if (TD->isLittleEndian()) {
130 for (signed i = len-1; i >= 0; i--) {
131 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
132 StrVal = (StrVal << 8) | SingleChar;
135 for (unsigned i = 0; i < len; i++) {
136 SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
137 StrVal = (StrVal << 8) | SingleChar;
139 // Append NULL at the end.
141 StrVal = (StrVal << 8) | SingleChar;
143 return ConstantInt::get(CE->getContext(), StrVal);
147 // If this load comes from anywhere in a constant global, and if the global
148 // is all undef or zero, we know what it loads.
149 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getUnderlyingObject())){
150 if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
151 const Type *ResTy = cast<PointerType>(C->getType())->getElementType();
152 if (GV->getInitializer()->isNullValue())
153 return Constant::getNullValue(ResTy);
154 if (isa<UndefValue>(GV->getInitializer()))
155 return UndefValue::get(ResTy);
162 static Constant *ConstantFoldLoadInst(const LoadInst *LI, const TargetData *TD){
163 if (LI->isVolatile()) return 0;
165 if (Constant *C = dyn_cast<Constant>(LI->getOperand(0)))
166 return ConstantFoldLoadFromConstPtr(C, TD);
171 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
172 /// Attempt to symbolically evaluate the result of a binary operator merging
173 /// these together. If target data info is available, it is provided as TD,
174 /// otherwise TD is null.
175 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
176 Constant *Op1, const TargetData *TD,
177 LLVMContext &Context){
180 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
181 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
185 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
186 // constant. This happens frequently when iterating over a global array.
187 if (Opc == Instruction::Sub && TD) {
188 GlobalValue *GV1, *GV2;
189 int64_t Offs1, Offs2;
191 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
192 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
194 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
195 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
202 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
203 /// constant expression, do so.
204 static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
205 const Type *ResultTy,
206 LLVMContext &Context,
207 const TargetData *TD) {
208 Constant *Ptr = Ops[0];
209 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
212 unsigned BitWidth = TD->getTypeSizeInBits(TD->getIntPtrType(Context));
213 APInt BasePtr(BitWidth, 0);
214 bool BaseIsInt = true;
215 if (!Ptr->isNullValue()) {
216 // If this is a inttoptr from a constant int, we can fold this as the base,
217 // otherwise we can't.
218 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
219 if (CE->getOpcode() == Instruction::IntToPtr)
220 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0))) {
221 BasePtr = Base->getValue();
222 BasePtr.zextOrTrunc(BitWidth);
229 // If this is a constant expr gep that is effectively computing an
230 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
231 for (unsigned i = 1; i != NumOps; ++i)
232 if (!isa<ConstantInt>(Ops[i]))
235 APInt Offset = APInt(BitWidth,
236 TD->getIndexedOffset(Ptr->getType(),
237 (Value**)Ops+1, NumOps-1));
238 // If the base value for this address is a literal integer value, fold the
239 // getelementptr to the resulting integer value casted to the pointer type.
241 Constant *C = ConstantInt::get(Context, Offset+BasePtr);
242 return ConstantExpr::getIntToPtr(C, ResultTy);
245 // Otherwise form a regular getelementptr. Recompute the indices so that
246 // we eliminate over-indexing of the notional static type array bounds.
247 // This makes it easy to determine if the getelementptr is "inbounds".
248 // Also, this helps GlobalOpt do SROA on GlobalVariables.
249 const Type *Ty = Ptr->getType();
250 SmallVector<Constant*, 32> NewIdxs;
252 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
253 // The only pointer indexing we'll do is on the first index of the GEP.
254 if (isa<PointerType>(ATy) && !NewIdxs.empty())
256 // Determine which element of the array the offset points into.
257 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
260 APInt NewIdx = Offset.udiv(ElemSize);
261 Offset -= NewIdx * ElemSize;
262 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx));
263 Ty = ATy->getElementType();
264 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
265 // Determine which field of the struct the offset points into. The
266 // getZExtValue is at least as safe as the StructLayout API because we
267 // know the offset is within the struct at this point.
268 const StructLayout &SL = *TD->getStructLayout(STy);
269 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
270 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx));
271 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
272 Ty = STy->getTypeAtIndex(ElIdx);
274 // We've reached some non-indexable type.
277 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
279 // If we haven't used up the entire offset by descending the static
280 // type, then the offset is pointing into the middle of an indivisible
281 // member, so we can't simplify it.
287 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
288 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
289 "Computed GetElementPtr has unexpected type!");
291 // If we ended up indexing a member with a type that doesn't match
292 // the type of what the original indices indexed, add a cast.
293 if (Ty != cast<PointerType>(ResultTy)->getElementType())
294 C = ConstantExpr::getBitCast(C, ResultTy);
299 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
300 /// targetdata. Return 0 if unfoldable.
301 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
302 const TargetData &TD, LLVMContext &Context) {
303 // If this is a bitcast from constant vector -> vector, fold it.
304 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
305 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
306 // If the element types match, VMCore can fold it.
307 unsigned NumDstElt = DestVTy->getNumElements();
308 unsigned NumSrcElt = CV->getNumOperands();
309 if (NumDstElt == NumSrcElt)
312 const Type *SrcEltTy = CV->getType()->getElementType();
313 const Type *DstEltTy = DestVTy->getElementType();
315 // Otherwise, we're changing the number of elements in a vector, which
316 // requires endianness information to do the right thing. For example,
317 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
318 // folds to (little endian):
319 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
320 // and to (big endian):
321 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
323 // First thing is first. We only want to think about integer here, so if
324 // we have something in FP form, recast it as integer.
325 if (DstEltTy->isFloatingPoint()) {
326 // Fold to an vector of integers with same size as our FP type.
327 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
328 const Type *DestIVTy = VectorType::get(
329 IntegerType::get(Context, FPWidth), NumDstElt);
330 // Recursively handle this integer conversion, if possible.
331 C = FoldBitCast(C, DestIVTy, TD, Context);
334 // Finally, VMCore can handle this now that #elts line up.
335 return ConstantExpr::getBitCast(C, DestTy);
338 // Okay, we know the destination is integer, if the input is FP, convert
339 // it to integer first.
340 if (SrcEltTy->isFloatingPoint()) {
341 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
342 const Type *SrcIVTy = VectorType::get(
343 IntegerType::get(Context, FPWidth), NumSrcElt);
344 // Ask VMCore to do the conversion now that #elts line up.
345 C = ConstantExpr::getBitCast(C, SrcIVTy);
346 CV = dyn_cast<ConstantVector>(C);
347 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
350 // Now we know that the input and output vectors are both integer vectors
351 // of the same size, and that their #elements is not the same. Do the
352 // conversion here, which depends on whether the input or output has
354 bool isLittleEndian = TD.isLittleEndian();
356 SmallVector<Constant*, 32> Result;
357 if (NumDstElt < NumSrcElt) {
358 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
359 Constant *Zero = Constant::getNullValue(DstEltTy);
360 unsigned Ratio = NumSrcElt/NumDstElt;
361 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
363 for (unsigned i = 0; i != NumDstElt; ++i) {
364 // Build each element of the result.
365 Constant *Elt = Zero;
366 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
367 for (unsigned j = 0; j != Ratio; ++j) {
368 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
369 if (!Src) return 0; // Reject constantexpr elements.
371 // Zero extend the element to the right size.
372 Src = ConstantExpr::getZExt(Src, Elt->getType());
374 // Shift it to the right place, depending on endianness.
375 Src = ConstantExpr::getShl(Src,
376 ConstantInt::get(Src->getType(), ShiftAmt));
377 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
380 Elt = ConstantExpr::getOr(Elt, Src);
382 Result.push_back(Elt);
385 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
386 unsigned Ratio = NumDstElt/NumSrcElt;
387 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
389 // Loop over each source value, expanding into multiple results.
390 for (unsigned i = 0; i != NumSrcElt; ++i) {
391 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
392 if (!Src) return 0; // Reject constantexpr elements.
394 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
395 for (unsigned j = 0; j != Ratio; ++j) {
396 // Shift the piece of the value into the right place, depending on
398 Constant *Elt = ConstantExpr::getLShr(Src,
399 ConstantInt::get(Src->getType(), ShiftAmt));
400 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
402 // Truncate and remember this piece.
403 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
408 return ConstantVector::get(Result.data(), Result.size());
416 //===----------------------------------------------------------------------===//
417 // Constant Folding public APIs
418 //===----------------------------------------------------------------------===//
421 /// ConstantFoldInstruction - Attempt to constant fold the specified
422 /// instruction. If successful, the constant result is returned, if not, null
423 /// is returned. Note that this function can only fail when attempting to fold
424 /// instructions like loads and stores, which have no constant expression form.
426 Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
427 const TargetData *TD) {
428 if (PHINode *PN = dyn_cast<PHINode>(I)) {
429 if (PN->getNumIncomingValues() == 0)
430 return UndefValue::get(PN->getType());
432 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
433 if (Result == 0) return 0;
435 // Handle PHI nodes specially here...
436 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
437 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
438 return 0; // Not all the same incoming constants...
440 // If we reach here, all incoming values are the same constant.
444 // Scan the operand list, checking to see if they are all constants, if so,
445 // hand off to ConstantFoldInstOperands.
446 SmallVector<Constant*, 8> Ops;
447 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
448 if (Constant *Op = dyn_cast<Constant>(*i))
451 return 0; // All operands not constant!
453 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
454 return ConstantFoldCompareInstOperands(CI->getPredicate(),
455 Ops.data(), Ops.size(),
458 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
459 return ConstantFoldLoadInst(LI, TD);
461 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
462 Ops.data(), Ops.size(), Context, TD);
465 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
466 /// using the specified TargetData. If successful, the constant result is
467 /// result is returned, if not, null is returned.
468 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
469 LLVMContext &Context,
470 const TargetData *TD) {
471 SmallVector<Constant*, 8> Ops;
472 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
473 Ops.push_back(cast<Constant>(*i));
476 return ConstantFoldCompareInstOperands(CE->getPredicate(),
477 Ops.data(), Ops.size(),
479 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
480 Ops.data(), Ops.size(), Context, TD);
483 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
484 /// specified opcode and operands. If successful, the constant result is
485 /// returned, if not, null is returned. Note that this function can fail when
486 /// attempting to fold instructions like loads and stores, which have no
487 /// constant expression form.
489 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
490 Constant* const* Ops, unsigned NumOps,
491 LLVMContext &Context,
492 const TargetData *TD) {
493 // Handle easy binops first.
494 if (Instruction::isBinaryOp(Opcode)) {
495 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
496 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
500 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
505 case Instruction::Call:
506 if (Function *F = dyn_cast<Function>(Ops[0]))
507 if (canConstantFoldCallTo(F))
508 return ConstantFoldCall(F, Ops+1, NumOps-1);
510 case Instruction::ICmp:
511 case Instruction::FCmp:
512 llvm_unreachable("This function is invalid for compares: no predicate specified");
513 case Instruction::PtrToInt:
514 // If the input is a inttoptr, eliminate the pair. This requires knowing
515 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
516 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
517 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
518 Constant *Input = CE->getOperand(0);
519 unsigned InWidth = Input->getType()->getScalarSizeInBits();
520 if (TD->getPointerSizeInBits() < InWidth) {
522 ConstantInt::get(Context, APInt::getLowBitsSet(InWidth,
523 TD->getPointerSizeInBits()));
524 Input = ConstantExpr::getAnd(Input, Mask);
526 // Do a zext or trunc to get to the dest size.
527 return ConstantExpr::getIntegerCast(Input, DestTy, false);
530 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
531 case Instruction::IntToPtr:
532 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
533 // the int size is >= the ptr size. This requires knowing the width of a
534 // pointer, so it can't be done in ConstantExpr::getCast.
535 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
537 TD->getPointerSizeInBits() <=
538 CE->getType()->getScalarSizeInBits()) {
539 if (CE->getOpcode() == Instruction::PtrToInt) {
540 Constant *Input = CE->getOperand(0);
541 Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
542 return C ? C : ConstantExpr::getBitCast(Input, DestTy);
544 // If there's a constant offset added to the integer value before
545 // it is casted back to a pointer, see if the expression can be
546 // converted into a GEP.
547 if (CE->getOpcode() == Instruction::Add)
548 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
549 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
550 if (R->getOpcode() == Instruction::PtrToInt)
551 if (GlobalVariable *GV =
552 dyn_cast<GlobalVariable>(R->getOperand(0))) {
553 const PointerType *GVTy = cast<PointerType>(GV->getType());
554 if (const ArrayType *AT =
555 dyn_cast<ArrayType>(GVTy->getElementType())) {
556 const Type *ElTy = AT->getElementType();
557 uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
558 APInt PSA(L->getValue().getBitWidth(), AllocSize);
559 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
560 L->getValue().urem(PSA) == 0) {
561 APInt ElemIdx = L->getValue().udiv(PSA);
562 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
563 AT->getNumElements()))) {
564 Constant *Index[] = {
565 Constant::getNullValue(CE->getType()),
566 ConstantInt::get(Context, ElemIdx)
569 ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
576 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
577 case Instruction::Trunc:
578 case Instruction::ZExt:
579 case Instruction::SExt:
580 case Instruction::FPTrunc:
581 case Instruction::FPExt:
582 case Instruction::UIToFP:
583 case Instruction::SIToFP:
584 case Instruction::FPToUI:
585 case Instruction::FPToSI:
586 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
587 case Instruction::BitCast:
589 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
591 return ConstantExpr::getBitCast(Ops[0], DestTy);
592 case Instruction::Select:
593 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
594 case Instruction::ExtractElement:
595 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
596 case Instruction::InsertElement:
597 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
598 case Instruction::ShuffleVector:
599 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
600 case Instruction::GetElementPtr:
601 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
604 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
608 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
609 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
610 /// returns a constant expression of the specified operands.
612 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
613 Constant*const * Ops,
615 LLVMContext &Context,
616 const TargetData *TD) {
617 // fold: icmp (inttoptr x), null -> icmp x, 0
618 // fold: icmp (ptrtoint x), 0 -> icmp x, null
619 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
620 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
622 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
623 // around to know if bit truncation is happening.
624 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
625 if (TD && Ops[1]->isNullValue()) {
626 const Type *IntPtrTy = TD->getIntPtrType(Context);
627 if (CE0->getOpcode() == Instruction::IntToPtr) {
628 // Convert the integer value to the right size to ensure we get the
629 // proper extension or truncation.
630 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
632 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
633 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
637 // Only do this transformation if the int is intptrty in size, otherwise
638 // there is a truncation or extension that we aren't modeling.
639 if (CE0->getOpcode() == Instruction::PtrToInt &&
640 CE0->getType() == IntPtrTy) {
641 Constant *C = CE0->getOperand(0);
642 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
644 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
649 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
650 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
651 const Type *IntPtrTy = TD->getIntPtrType(Context);
653 if (CE0->getOpcode() == Instruction::IntToPtr) {
654 // Convert the integer value to the right size to ensure we get the
655 // proper extension or truncation.
656 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
658 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
660 Constant *NewOps[] = { C0, C1 };
661 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
665 // Only do this transformation if the int is intptrty in size, otherwise
666 // there is a truncation or extension that we aren't modeling.
667 if ((CE0->getOpcode() == Instruction::PtrToInt &&
668 CE0->getType() == IntPtrTy &&
669 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
670 Constant *NewOps[] = {
671 CE0->getOperand(0), CE1->getOperand(0)
673 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
679 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
683 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
684 /// getelementptr constantexpr, return the constant value being addressed by the
685 /// constant expression, or null if something is funny and we can't decide.
686 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
688 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
689 return 0; // Do not allow stepping over the value!
691 // Loop over all of the operands, tracking down which value we are
693 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
694 for (++I; I != E; ++I)
695 if (const StructType *STy = dyn_cast<StructType>(*I)) {
696 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
697 assert(CU->getZExtValue() < STy->getNumElements() &&
698 "Struct index out of range!");
699 unsigned El = (unsigned)CU->getZExtValue();
700 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
701 C = CS->getOperand(El);
702 } else if (isa<ConstantAggregateZero>(C)) {
703 C = Constant::getNullValue(STy->getElementType(El));
704 } else if (isa<UndefValue>(C)) {
705 C = UndefValue::get(STy->getElementType(El));
709 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
710 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
711 if (CI->getZExtValue() >= ATy->getNumElements())
713 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
714 C = CA->getOperand(CI->getZExtValue());
715 else if (isa<ConstantAggregateZero>(C))
716 C = Constant::getNullValue(ATy->getElementType());
717 else if (isa<UndefValue>(C))
718 C = UndefValue::get(ATy->getElementType());
721 } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) {
722 if (CI->getZExtValue() >= VTy->getNumElements())
724 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
725 C = CP->getOperand(CI->getZExtValue());
726 else if (isa<ConstantAggregateZero>(C))
727 C = Constant::getNullValue(VTy->getElementType());
728 else if (isa<UndefValue>(C))
729 C = UndefValue::get(VTy->getElementType());
742 //===----------------------------------------------------------------------===//
743 // Constant Folding for Calls
746 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
747 /// the specified function.
749 llvm::canConstantFoldCallTo(const Function *F) {
750 switch (F->getIntrinsicID()) {
751 case Intrinsic::sqrt:
752 case Intrinsic::powi:
753 case Intrinsic::bswap:
754 case Intrinsic::ctpop:
755 case Intrinsic::ctlz:
756 case Intrinsic::cttz:
757 case Intrinsic::uadd_with_overflow:
758 case Intrinsic::usub_with_overflow:
759 case Intrinsic::sadd_with_overflow:
760 case Intrinsic::ssub_with_overflow:
767 if (!F->hasName()) return false;
768 StringRef Name = F->getName();
770 // In these cases, the check of the length is required. We don't want to
771 // return true for a name like "cos\0blah" which strcmp would return equal to
772 // "cos", but has length 8.
774 default: return false;
776 return Name == "acos" || Name == "asin" ||
777 Name == "atan" || Name == "atan2";
779 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
781 return Name == "exp";
783 return Name == "fabs" || Name == "fmod" || Name == "floor";
785 return Name == "log" || Name == "log10";
787 return Name == "pow";
789 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
790 Name == "sinf" || Name == "sqrtf";
792 return Name == "tan" || Name == "tanh";
796 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
797 const Type *Ty, LLVMContext &Context) {
806 return ConstantFP::get(Context, APFloat((float)V));
807 if (Ty->isDoubleTy())
808 return ConstantFP::get(Context, APFloat(V));
809 llvm_unreachable("Can only constant fold float/double");
810 return 0; // dummy return to suppress warning
813 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
816 LLVMContext &Context) {
825 return ConstantFP::get(Context, APFloat((float)V));
826 if (Ty->isDoubleTy())
827 return ConstantFP::get(Context, APFloat(V));
828 llvm_unreachable("Can only constant fold float/double");
829 return 0; // dummy return to suppress warning
832 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
833 /// with the specified arguments, returning null if unsuccessful.
835 llvm::ConstantFoldCall(Function *F,
836 Constant *const *Operands, unsigned NumOperands) {
837 if (!F->hasName()) return 0;
838 LLVMContext &Context = F->getContext();
839 StringRef Name = F->getName();
841 const Type *Ty = F->getReturnType();
842 if (NumOperands == 1) {
843 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
844 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
846 /// Currently APFloat versions of these functions do not exist, so we use
847 /// the host native double versions. Float versions are not called
848 /// directly but for all these it is true (float)(f((double)arg)) ==
849 /// f(arg). Long double not supported yet.
850 double V = Ty->isFloatTy() ? (double)Op->getValueAPF().convertToFloat() :
851 Op->getValueAPF().convertToDouble();
855 return ConstantFoldFP(acos, V, Ty, Context);
856 else if (Name == "asin")
857 return ConstantFoldFP(asin, V, Ty, Context);
858 else if (Name == "atan")
859 return ConstantFoldFP(atan, V, Ty, Context);
863 return ConstantFoldFP(ceil, V, Ty, Context);
864 else if (Name == "cos")
865 return ConstantFoldFP(cos, V, Ty, Context);
866 else if (Name == "cosh")
867 return ConstantFoldFP(cosh, V, Ty, Context);
868 else if (Name == "cosf")
869 return ConstantFoldFP(cos, V, Ty, Context);
873 return ConstantFoldFP(exp, V, Ty, Context);
877 return ConstantFoldFP(fabs, V, Ty, Context);
878 else if (Name == "floor")
879 return ConstantFoldFP(floor, V, Ty, Context);
882 if (Name == "log" && V > 0)
883 return ConstantFoldFP(log, V, Ty, Context);
884 else if (Name == "log10" && V > 0)
885 return ConstantFoldFP(log10, V, Ty, Context);
886 else if (Name == "llvm.sqrt.f32" ||
887 Name == "llvm.sqrt.f64") {
889 return ConstantFoldFP(sqrt, V, Ty, Context);
891 return Constant::getNullValue(Ty);
896 return ConstantFoldFP(sin, V, Ty, Context);
897 else if (Name == "sinh")
898 return ConstantFoldFP(sinh, V, Ty, Context);
899 else if (Name == "sqrt" && V >= 0)
900 return ConstantFoldFP(sqrt, V, Ty, Context);
901 else if (Name == "sqrtf" && V >= 0)
902 return ConstantFoldFP(sqrt, V, Ty, Context);
903 else if (Name == "sinf")
904 return ConstantFoldFP(sin, V, Ty, Context);
908 return ConstantFoldFP(tan, V, Ty, Context);
909 else if (Name == "tanh")
910 return ConstantFoldFP(tanh, V, Ty, Context);
919 if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
920 if (Name.startswith("llvm.bswap"))
921 return ConstantInt::get(Context, Op->getValue().byteSwap());
922 else if (Name.startswith("llvm.ctpop"))
923 return ConstantInt::get(Ty, Op->getValue().countPopulation());
924 else if (Name.startswith("llvm.cttz"))
925 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
926 else if (Name.startswith("llvm.ctlz"))
927 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
934 if (NumOperands == 2) {
935 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
936 if (!Ty->isFloatTy() && !Ty->isDoubleTy())
938 double Op1V = Ty->isFloatTy() ?
939 (double)Op1->getValueAPF().convertToFloat() :
940 Op1->getValueAPF().convertToDouble();
941 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
942 if (Op2->getType() != Op1->getType())
945 double Op2V = Ty->isFloatTy() ?
946 (double)Op2->getValueAPF().convertToFloat():
947 Op2->getValueAPF().convertToDouble();
950 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context);
952 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context);
954 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context);
955 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
956 if (Name == "llvm.powi.f32")
957 return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V,
958 (int)Op2C->getZExtValue())));
959 if (Name == "llvm.powi.f64")
960 return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V,
961 (int)Op2C->getZExtValue())));
967 if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
968 if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
969 switch (F->getIntrinsicID()) {
971 case Intrinsic::uadd_with_overflow: {
972 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
974 Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
976 return ConstantStruct::get(F->getContext(), Ops, 2, false);
978 case Intrinsic::usub_with_overflow: {
979 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
981 Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
983 return ConstantStruct::get(F->getContext(), Ops, 2, false);
985 case Intrinsic::sadd_with_overflow: {
986 Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
987 Constant *Overflow = ConstantExpr::getSelect(
988 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
989 ConstantInt::get(Op1->getType(), 0), Op1),
990 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op2),
991 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op2)); // overflow.
993 Constant *Ops[] = { Res, Overflow };
994 return ConstantStruct::get(F->getContext(), Ops, 2, false);
996 case Intrinsic::ssub_with_overflow: {
997 Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
998 Constant *Overflow = ConstantExpr::getSelect(
999 ConstantExpr::getICmp(CmpInst::ICMP_SGT,
1000 ConstantInt::get(Op2->getType(), 0), Op2),
1001 ConstantExpr::getICmp(CmpInst::ICMP_SLT, Res, Op1),
1002 ConstantExpr::getICmp(CmpInst::ICMP_SGT, Res, Op1)); // overflow.
1004 Constant *Ops[] = { Res, Overflow };
1005 return ConstantStruct::get(F->getContext(), Ops, 2, false);