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/LLVMContext.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/StringMap.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Support/GetElementPtrTypeIterator.h"
28 #include "llvm/Support/MathExtras.h"
33 //===----------------------------------------------------------------------===//
34 // Constant Folding internal helper functions
35 //===----------------------------------------------------------------------===//
37 /// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
38 /// from a global, return the global and the constant. Because of
39 /// constantexprs, this function is recursive.
40 static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
41 int64_t &Offset, const TargetData &TD) {
42 // Trivial case, constant is the global.
43 if ((GV = dyn_cast<GlobalValue>(C))) {
48 // Otherwise, if this isn't a constant expr, bail out.
49 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
50 if (!CE) return false;
52 // Look through ptr->int and ptr->ptr casts.
53 if (CE->getOpcode() == Instruction::PtrToInt ||
54 CE->getOpcode() == Instruction::BitCast)
55 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
57 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
58 if (CE->getOpcode() == Instruction::GetElementPtr) {
59 // Cannot compute this if the element type of the pointer is missing size
61 if (!cast<PointerType>(CE->getOperand(0)->getType())
62 ->getElementType()->isSized())
65 // If the base isn't a global+constant, we aren't either.
66 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
69 // Otherwise, add any offset that our operands provide.
70 gep_type_iterator GTI = gep_type_begin(CE);
71 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
73 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
74 if (!CI) return false; // Index isn't a simple constant?
75 if (CI->getZExtValue() == 0) continue; // Not adding anything.
77 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
79 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
81 const SequentialType *SQT = cast<SequentialType>(*GTI);
82 Offset += TD.getTypeAllocSize(SQT->getElementType())*CI->getSExtValue();
92 /// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
93 /// Attempt to symbolically evaluate the result of a binary operator merging
94 /// these together. If target data info is available, it is provided as TD,
95 /// otherwise TD is null.
96 static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
97 Constant *Op1, const TargetData *TD,
98 LLVMContext &Context){
101 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
102 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
106 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
107 // constant. This happens frequently when iterating over a global array.
108 if (Opc == Instruction::Sub && TD) {
109 GlobalValue *GV1, *GV2;
110 int64_t Offs1, Offs2;
112 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
113 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
115 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
116 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
123 /// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
124 /// constant expression, do so.
125 static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
126 const Type *ResultTy,
127 LLVMContext &Context,
128 const TargetData *TD) {
129 Constant *Ptr = Ops[0];
130 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
133 unsigned BitWidth = TD->getTypeSizeInBits(TD->getIntPtrType(Context));
134 APInt BasePtr(BitWidth, 0);
135 bool BaseIsInt = true;
136 if (!Ptr->isNullValue()) {
137 // If this is a inttoptr from a constant int, we can fold this as the base,
138 // otherwise we can't.
139 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
140 if (CE->getOpcode() == Instruction::IntToPtr)
141 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
142 BasePtr = Base->getValue();
148 // If this is a constant expr gep that is effectively computing an
149 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
150 for (unsigned i = 1; i != NumOps; ++i)
151 if (!isa<ConstantInt>(Ops[i]))
154 APInt Offset = APInt(BitWidth,
155 TD->getIndexedOffset(Ptr->getType(),
156 (Value**)Ops+1, NumOps-1));
157 // If the base value for this address is a literal integer value, fold the
158 // getelementptr to the resulting integer value casted to the pointer type.
160 Constant *C = ConstantInt::get(Context, Offset+BasePtr);
161 return ConstantExpr::getIntToPtr(C, ResultTy);
164 // Otherwise form a regular getelementptr. Recompute the indices so that
165 // we eliminate over-indexing of the notional static type array bounds.
166 // This makes it easy to determine if the getelementptr is "inbounds".
167 // Also, this helps GlobalOpt do SROA on GlobalVariables.
168 const Type *Ty = Ptr->getType();
169 SmallVector<Constant*, 32> NewIdxs;
171 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
172 // The only pointer indexing we'll do is on the first index of the GEP.
173 if (isa<PointerType>(ATy) && ATy != Ptr->getType())
175 // Determine which element of the array the offset points into.
176 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
179 APInt NewIdx = Offset.udiv(ElemSize);
180 Offset -= NewIdx * ElemSize;
181 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx));
182 Ty = ATy->getElementType();
183 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
184 // Determine which field of the struct the offset points into. The
185 // getZExtValue is at least as safe as the StructLayout API because we
186 // know the offset is within the struct at this point.
187 const StructLayout &SL = *TD->getStructLayout(STy);
188 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
189 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx));
190 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
191 Ty = STy->getTypeAtIndex(ElIdx);
193 // We've reached some non-indexable type.
196 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
198 // If we haven't used up the entire offset by descending the static
199 // type, then the offset is pointing into the middle of an indivisible
200 // member, so we can't simplify it.
204 // If the base is the start of a GlobalVariable and all the array indices
205 // remain in their static bounds, the GEP is inbounds. We can check that
206 // all indices are in bounds by just checking the first index only
207 // because we've just normalized all the indices.
208 Constant *C = isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue() ?
209 ConstantExpr::getInBoundsGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()) :
210 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
211 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
212 "Computed GetElementPtr has unexpected type!");
214 // If we ended up indexing a member with a type that doesn't match
215 // the type of what the original indices indexed, add a cast.
216 if (Ty != cast<PointerType>(ResultTy)->getElementType())
217 C = ConstantExpr::getBitCast(C, ResultTy);
222 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
223 /// targetdata. Return 0 if unfoldable.
224 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
225 const TargetData &TD, LLVMContext &Context) {
226 // If this is a bitcast from constant vector -> vector, fold it.
227 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
228 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
229 // If the element types match, VMCore can fold it.
230 unsigned NumDstElt = DestVTy->getNumElements();
231 unsigned NumSrcElt = CV->getNumOperands();
232 if (NumDstElt == NumSrcElt)
235 const Type *SrcEltTy = CV->getType()->getElementType();
236 const Type *DstEltTy = DestVTy->getElementType();
238 // Otherwise, we're changing the number of elements in a vector, which
239 // requires endianness information to do the right thing. For example,
240 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
241 // folds to (little endian):
242 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
243 // and to (big endian):
244 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
246 // First thing is first. We only want to think about integer here, so if
247 // we have something in FP form, recast it as integer.
248 if (DstEltTy->isFloatingPoint()) {
249 // Fold to an vector of integers with same size as our FP type.
250 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
251 const Type *DestIVTy = VectorType::get(
252 IntegerType::get(Context, FPWidth), NumDstElt);
253 // Recursively handle this integer conversion, if possible.
254 C = FoldBitCast(C, DestIVTy, TD, Context);
257 // Finally, VMCore can handle this now that #elts line up.
258 return ConstantExpr::getBitCast(C, DestTy);
261 // Okay, we know the destination is integer, if the input is FP, convert
262 // it to integer first.
263 if (SrcEltTy->isFloatingPoint()) {
264 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
265 const Type *SrcIVTy = VectorType::get(
266 IntegerType::get(Context, FPWidth), NumSrcElt);
267 // Ask VMCore to do the conversion now that #elts line up.
268 C = ConstantExpr::getBitCast(C, SrcIVTy);
269 CV = dyn_cast<ConstantVector>(C);
270 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
273 // Now we know that the input and output vectors are both integer vectors
274 // of the same size, and that their #elements is not the same. Do the
275 // conversion here, which depends on whether the input or output has
277 bool isLittleEndian = TD.isLittleEndian();
279 SmallVector<Constant*, 32> Result;
280 if (NumDstElt < NumSrcElt) {
281 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
282 Constant *Zero = Constant::getNullValue(DstEltTy);
283 unsigned Ratio = NumSrcElt/NumDstElt;
284 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
286 for (unsigned i = 0; i != NumDstElt; ++i) {
287 // Build each element of the result.
288 Constant *Elt = Zero;
289 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
290 for (unsigned j = 0; j != Ratio; ++j) {
291 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
292 if (!Src) return 0; // Reject constantexpr elements.
294 // Zero extend the element to the right size.
295 Src = ConstantExpr::getZExt(Src, Elt->getType());
297 // Shift it to the right place, depending on endianness.
298 Src = ConstantExpr::getShl(Src,
299 ConstantInt::get(Src->getType(), ShiftAmt));
300 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
303 Elt = ConstantExpr::getOr(Elt, Src);
305 Result.push_back(Elt);
308 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
309 unsigned Ratio = NumDstElt/NumSrcElt;
310 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
312 // Loop over each source value, expanding into multiple results.
313 for (unsigned i = 0; i != NumSrcElt; ++i) {
314 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
315 if (!Src) return 0; // Reject constantexpr elements.
317 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
318 for (unsigned j = 0; j != Ratio; ++j) {
319 // Shift the piece of the value into the right place, depending on
321 Constant *Elt = ConstantExpr::getLShr(Src,
322 ConstantInt::get(Src->getType(), ShiftAmt));
323 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
325 // Truncate and remember this piece.
326 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
331 return ConstantVector::get(Result.data(), Result.size());
339 //===----------------------------------------------------------------------===//
340 // Constant Folding public APIs
341 //===----------------------------------------------------------------------===//
344 /// ConstantFoldInstruction - Attempt to constant fold the specified
345 /// instruction. If successful, the constant result is returned, if not, null
346 /// is returned. Note that this function can only fail when attempting to fold
347 /// instructions like loads and stores, which have no constant expression form.
349 Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
350 const TargetData *TD) {
351 if (PHINode *PN = dyn_cast<PHINode>(I)) {
352 if (PN->getNumIncomingValues() == 0)
353 return UndefValue::get(PN->getType());
355 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
356 if (Result == 0) return 0;
358 // Handle PHI nodes specially here...
359 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
360 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
361 return 0; // Not all the same incoming constants...
363 // If we reach here, all incoming values are the same constant.
367 // Scan the operand list, checking to see if they are all constants, if so,
368 // hand off to ConstantFoldInstOperands.
369 SmallVector<Constant*, 8> Ops;
370 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
371 if (Constant *Op = dyn_cast<Constant>(*i))
374 return 0; // All operands not constant!
376 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
377 return ConstantFoldCompareInstOperands(CI->getPredicate(),
378 Ops.data(), Ops.size(),
381 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
382 Ops.data(), Ops.size(), Context, TD);
385 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
386 /// using the specified TargetData. If successful, the constant result is
387 /// result is returned, if not, null is returned.
388 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
389 LLVMContext &Context,
390 const TargetData *TD) {
391 SmallVector<Constant*, 8> Ops;
392 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
393 Ops.push_back(cast<Constant>(*i));
396 return ConstantFoldCompareInstOperands(CE->getPredicate(),
397 Ops.data(), Ops.size(),
400 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
401 Ops.data(), Ops.size(), Context, TD);
404 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
405 /// specified opcode and operands. If successful, the constant result is
406 /// returned, if not, null is returned. Note that this function can fail when
407 /// attempting to fold instructions like loads and stores, which have no
408 /// constant expression form.
410 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
411 Constant* const* Ops, unsigned NumOps,
412 LLVMContext &Context,
413 const TargetData *TD) {
414 // Handle easy binops first.
415 if (Instruction::isBinaryOp(Opcode)) {
416 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
417 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
421 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
426 case Instruction::Call:
427 if (Function *F = dyn_cast<Function>(Ops[0]))
428 if (canConstantFoldCallTo(F))
429 return ConstantFoldCall(F, Ops+1, NumOps-1);
431 case Instruction::ICmp:
432 case Instruction::FCmp:
433 llvm_unreachable("This function is invalid for compares: no predicate specified");
434 case Instruction::PtrToInt:
435 // If the input is a inttoptr, eliminate the pair. This requires knowing
436 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
437 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
438 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
439 Constant *Input = CE->getOperand(0);
440 unsigned InWidth = Input->getType()->getScalarSizeInBits();
441 if (TD->getPointerSizeInBits() < InWidth) {
443 ConstantInt::get(Context, APInt::getLowBitsSet(InWidth,
444 TD->getPointerSizeInBits()));
445 Input = ConstantExpr::getAnd(Input, Mask);
447 // Do a zext or trunc to get to the dest size.
448 return ConstantExpr::getIntegerCast(Input, DestTy, false);
451 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
452 case Instruction::IntToPtr:
453 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
454 // the int size is >= the ptr size. This requires knowing the width of a
455 // pointer, so it can't be done in ConstantExpr::getCast.
456 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
458 TD->getPointerSizeInBits() <=
459 CE->getType()->getScalarSizeInBits()) {
460 if (CE->getOpcode() == Instruction::PtrToInt) {
461 Constant *Input = CE->getOperand(0);
462 Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
463 return C ? C : ConstantExpr::getBitCast(Input, DestTy);
465 // If there's a constant offset added to the integer value before
466 // it is casted back to a pointer, see if the expression can be
467 // converted into a GEP.
468 if (CE->getOpcode() == Instruction::Add)
469 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
470 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
471 if (R->getOpcode() == Instruction::PtrToInt)
472 if (GlobalVariable *GV =
473 dyn_cast<GlobalVariable>(R->getOperand(0))) {
474 const PointerType *GVTy = cast<PointerType>(GV->getType());
475 if (const ArrayType *AT =
476 dyn_cast<ArrayType>(GVTy->getElementType())) {
477 const Type *ElTy = AT->getElementType();
478 uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
479 APInt PSA(L->getValue().getBitWidth(), AllocSize);
480 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
481 L->getValue().urem(PSA) == 0) {
482 APInt ElemIdx = L->getValue().udiv(PSA);
483 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
484 AT->getNumElements()))) {
485 Constant *Index[] = {
486 Constant::getNullValue(CE->getType()),
487 ConstantInt::get(Context, ElemIdx)
490 ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
497 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
498 case Instruction::Trunc:
499 case Instruction::ZExt:
500 case Instruction::SExt:
501 case Instruction::FPTrunc:
502 case Instruction::FPExt:
503 case Instruction::UIToFP:
504 case Instruction::SIToFP:
505 case Instruction::FPToUI:
506 case Instruction::FPToSI:
507 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
508 case Instruction::BitCast:
510 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
512 return ConstantExpr::getBitCast(Ops[0], DestTy);
513 case Instruction::Select:
514 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
515 case Instruction::ExtractElement:
516 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
517 case Instruction::InsertElement:
518 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
519 case Instruction::ShuffleVector:
520 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
521 case Instruction::GetElementPtr:
522 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
525 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
529 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
530 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
531 /// returns a constant expression of the specified operands.
533 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
534 Constant*const * Ops,
536 LLVMContext &Context,
537 const TargetData *TD) {
538 // fold: icmp (inttoptr x), null -> icmp x, 0
539 // fold: icmp (ptrtoint x), 0 -> icmp x, null
540 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
541 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
543 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
544 // around to know if bit truncation is happening.
545 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
546 if (TD && Ops[1]->isNullValue()) {
547 const Type *IntPtrTy = TD->getIntPtrType(Context);
548 if (CE0->getOpcode() == Instruction::IntToPtr) {
549 // Convert the integer value to the right size to ensure we get the
550 // proper extension or truncation.
551 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
553 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
554 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
558 // Only do this transformation if the int is intptrty in size, otherwise
559 // there is a truncation or extension that we aren't modeling.
560 if (CE0->getOpcode() == Instruction::PtrToInt &&
561 CE0->getType() == IntPtrTy) {
562 Constant *C = CE0->getOperand(0);
563 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
565 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
570 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
571 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
572 const Type *IntPtrTy = TD->getIntPtrType(Context);
574 if (CE0->getOpcode() == Instruction::IntToPtr) {
575 // Convert the integer value to the right size to ensure we get the
576 // proper extension or truncation.
577 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
579 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
581 Constant *NewOps[] = { C0, C1 };
582 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
586 // Only do this transformation if the int is intptrty in size, otherwise
587 // there is a truncation or extension that we aren't modeling.
588 if ((CE0->getOpcode() == Instruction::PtrToInt &&
589 CE0->getType() == IntPtrTy &&
590 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
591 Constant *NewOps[] = {
592 CE0->getOperand(0), CE1->getOperand(0)
594 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
600 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
604 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
605 /// getelementptr constantexpr, return the constant value being addressed by the
606 /// constant expression, or null if something is funny and we can't decide.
607 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
609 LLVMContext &Context) {
610 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
611 return 0; // Do not allow stepping over the value!
613 // Loop over all of the operands, tracking down which value we are
615 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
616 for (++I; I != E; ++I)
617 if (const StructType *STy = dyn_cast<StructType>(*I)) {
618 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
619 assert(CU->getZExtValue() < STy->getNumElements() &&
620 "Struct index out of range!");
621 unsigned El = (unsigned)CU->getZExtValue();
622 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
623 C = CS->getOperand(El);
624 } else if (isa<ConstantAggregateZero>(C)) {
625 C = Constant::getNullValue(STy->getElementType(El));
626 } else if (isa<UndefValue>(C)) {
627 C = UndefValue::get(STy->getElementType(El));
631 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
632 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
633 if (CI->getZExtValue() >= ATy->getNumElements())
635 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
636 C = CA->getOperand(CI->getZExtValue());
637 else if (isa<ConstantAggregateZero>(C))
638 C = Constant::getNullValue(ATy->getElementType());
639 else if (isa<UndefValue>(C))
640 C = UndefValue::get(ATy->getElementType());
643 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
644 if (CI->getZExtValue() >= PTy->getNumElements())
646 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
647 C = CP->getOperand(CI->getZExtValue());
648 else if (isa<ConstantAggregateZero>(C))
649 C = Constant::getNullValue(PTy->getElementType());
650 else if (isa<UndefValue>(C))
651 C = UndefValue::get(PTy->getElementType());
664 //===----------------------------------------------------------------------===//
665 // Constant Folding for Calls
668 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
669 /// the specified function.
671 llvm::canConstantFoldCallTo(const Function *F) {
672 switch (F->getIntrinsicID()) {
673 case Intrinsic::sqrt:
674 case Intrinsic::powi:
675 case Intrinsic::bswap:
676 case Intrinsic::ctpop:
677 case Intrinsic::ctlz:
678 case Intrinsic::cttz:
683 if (!F->hasName()) return false;
684 StringRef Name = F->getName();
686 // In these cases, the check of the length is required. We don't want to
687 // return true for a name like "cos\0blah" which strcmp would return equal to
688 // "cos", but has length 8.
690 default: return false;
692 return Name == "acos" || Name == "asin" ||
693 Name == "atan" || Name == "atan2";
695 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
697 return Name == "exp";
699 return Name == "fabs" || Name == "fmod" || Name == "floor";
701 return Name == "log" || Name == "log10";
703 return Name == "pow";
705 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
706 Name == "sinf" || Name == "sqrtf";
708 return Name == "tan" || Name == "tanh";
712 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
713 const Type *Ty, LLVMContext &Context) {
721 if (Ty == Type::getFloatTy(Context))
722 return ConstantFP::get(Context, APFloat((float)V));
723 if (Ty == Type::getDoubleTy(Context))
724 return ConstantFP::get(Context, APFloat(V));
725 llvm_unreachable("Can only constant fold float/double");
726 return 0; // dummy return to suppress warning
729 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
732 LLVMContext &Context) {
740 if (Ty == Type::getFloatTy(Context))
741 return ConstantFP::get(Context, APFloat((float)V));
742 if (Ty == Type::getDoubleTy(Context))
743 return ConstantFP::get(Context, APFloat(V));
744 llvm_unreachable("Can only constant fold float/double");
745 return 0; // dummy return to suppress warning
748 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
749 /// with the specified arguments, returning null if unsuccessful.
752 llvm::ConstantFoldCall(Function *F,
753 Constant* const* Operands, unsigned NumOperands) {
754 if (!F->hasName()) return 0;
755 LLVMContext &Context = F->getContext();
756 StringRef Name = F->getName();
758 const Type *Ty = F->getReturnType();
759 if (NumOperands == 1) {
760 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
761 if (Ty!=Type::getFloatTy(F->getContext()) &&
762 Ty!=Type::getDoubleTy(Context))
764 /// Currently APFloat versions of these functions do not exist, so we use
765 /// the host native double versions. Float versions are not called
766 /// directly but for all these it is true (float)(f((double)arg)) ==
767 /// f(arg). Long double not supported yet.
768 double V = Ty==Type::getFloatTy(F->getContext()) ?
769 (double)Op->getValueAPF().convertToFloat():
770 Op->getValueAPF().convertToDouble();
774 return ConstantFoldFP(acos, V, Ty, Context);
775 else if (Name == "asin")
776 return ConstantFoldFP(asin, V, Ty, Context);
777 else if (Name == "atan")
778 return ConstantFoldFP(atan, V, Ty, Context);
782 return ConstantFoldFP(ceil, V, Ty, Context);
783 else if (Name == "cos")
784 return ConstantFoldFP(cos, V, Ty, Context);
785 else if (Name == "cosh")
786 return ConstantFoldFP(cosh, V, Ty, Context);
787 else if (Name == "cosf")
788 return ConstantFoldFP(cos, V, Ty, Context);
792 return ConstantFoldFP(exp, V, Ty, Context);
796 return ConstantFoldFP(fabs, V, Ty, Context);
797 else if (Name == "floor")
798 return ConstantFoldFP(floor, V, Ty, Context);
801 if (Name == "log" && V > 0)
802 return ConstantFoldFP(log, V, Ty, Context);
803 else if (Name == "log10" && V > 0)
804 return ConstantFoldFP(log10, V, Ty, Context);
805 else if (Name == "llvm.sqrt.f32" ||
806 Name == "llvm.sqrt.f64") {
808 return ConstantFoldFP(sqrt, V, Ty, Context);
810 return Constant::getNullValue(Ty);
815 return ConstantFoldFP(sin, V, Ty, Context);
816 else if (Name == "sinh")
817 return ConstantFoldFP(sinh, V, Ty, Context);
818 else if (Name == "sqrt" && V >= 0)
819 return ConstantFoldFP(sqrt, V, Ty, Context);
820 else if (Name == "sqrtf" && V >= 0)
821 return ConstantFoldFP(sqrt, V, Ty, Context);
822 else if (Name == "sinf")
823 return ConstantFoldFP(sin, V, Ty, Context);
827 return ConstantFoldFP(tan, V, Ty, Context);
828 else if (Name == "tanh")
829 return ConstantFoldFP(tanh, V, Ty, Context);
834 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
835 if (Name.startswith("llvm.bswap"))
836 return ConstantInt::get(Context, Op->getValue().byteSwap());
837 else if (Name.startswith("llvm.ctpop"))
838 return ConstantInt::get(Ty, Op->getValue().countPopulation());
839 else if (Name.startswith("llvm.cttz"))
840 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
841 else if (Name.startswith("llvm.ctlz"))
842 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
844 } else if (NumOperands == 2) {
845 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
846 if (Ty!=Type::getFloatTy(F->getContext()) &&
847 Ty!=Type::getDoubleTy(Context))
849 double Op1V = Ty==Type::getFloatTy(F->getContext()) ?
850 (double)Op1->getValueAPF().convertToFloat():
851 Op1->getValueAPF().convertToDouble();
852 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
853 double Op2V = Ty==Type::getFloatTy(F->getContext()) ?
854 (double)Op2->getValueAPF().convertToFloat():
855 Op2->getValueAPF().convertToDouble();
858 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context);
859 } else if (Name == "fmod") {
860 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context);
861 } else if (Name == "atan2") {
862 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context);
864 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
865 if (Name == "llvm.powi.f32") {
866 return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V,
867 (int)Op2C->getZExtValue())));
868 } else if (Name == "llvm.powi.f64") {
869 return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V,
870 (int)Op2C->getZExtValue())));