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();
143 BasePtr.zextOrTrunc(BitWidth);
150 // If this is a constant expr gep that is effectively computing an
151 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
152 for (unsigned i = 1; i != NumOps; ++i)
153 if (!isa<ConstantInt>(Ops[i]))
156 APInt Offset = APInt(BitWidth,
157 TD->getIndexedOffset(Ptr->getType(),
158 (Value**)Ops+1, NumOps-1));
159 // If the base value for this address is a literal integer value, fold the
160 // getelementptr to the resulting integer value casted to the pointer type.
162 Constant *C = ConstantInt::get(Context, Offset+BasePtr);
163 return ConstantExpr::getIntToPtr(C, ResultTy);
166 // Otherwise form a regular getelementptr. Recompute the indices so that
167 // we eliminate over-indexing of the notional static type array bounds.
168 // This makes it easy to determine if the getelementptr is "inbounds".
169 // Also, this helps GlobalOpt do SROA on GlobalVariables.
170 const Type *Ty = Ptr->getType();
171 SmallVector<Constant*, 32> NewIdxs;
173 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
174 // The only pointer indexing we'll do is on the first index of the GEP.
175 if (isa<PointerType>(ATy) && !NewIdxs.empty())
177 // Determine which element of the array the offset points into.
178 APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
181 APInt NewIdx = Offset.udiv(ElemSize);
182 Offset -= NewIdx * ElemSize;
183 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx));
184 Ty = ATy->getElementType();
185 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
186 // Determine which field of the struct the offset points into. The
187 // getZExtValue is at least as safe as the StructLayout API because we
188 // know the offset is within the struct at this point.
189 const StructLayout &SL = *TD->getStructLayout(STy);
190 unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
191 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx));
192 Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
193 Ty = STy->getTypeAtIndex(ElIdx);
195 // We've reached some non-indexable type.
198 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
200 // If we haven't used up the entire offset by descending the static
201 // type, then the offset is pointing into the middle of an indivisible
202 // member, so we can't simplify it.
206 // Create the GEP constant expr.
207 Constant *C = ConstantExpr::getGetElementPtr(Ptr,
208 &NewIdxs[0], NewIdxs.size());
209 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
210 "Computed GetElementPtr has unexpected type!");
212 // If the base is the start of a GlobalVariable and all the array indices
213 // remain in their static bounds, the GEP is inbounds. We can check that
214 // all indices are in bounds by just checking the first index only
215 // because we've just normalized all the indices. We can mutate the
216 // Constant in place because we've proven that the indices are in bounds,
217 // so they'll always be in bounds.
218 if (isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue())
219 if (GEPOperator *GEP = dyn_cast<GEPOperator>(C))
220 GEP->setIsInBounds(true);
222 // If we ended up indexing a member with a type that doesn't match
223 // the type of what the original indices indexed, add a cast.
224 if (Ty != cast<PointerType>(ResultTy)->getElementType())
225 C = ConstantExpr::getBitCast(C, ResultTy);
230 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
231 /// targetdata. Return 0 if unfoldable.
232 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
233 const TargetData &TD, LLVMContext &Context) {
234 // If this is a bitcast from constant vector -> vector, fold it.
235 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
236 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
237 // If the element types match, VMCore can fold it.
238 unsigned NumDstElt = DestVTy->getNumElements();
239 unsigned NumSrcElt = CV->getNumOperands();
240 if (NumDstElt == NumSrcElt)
243 const Type *SrcEltTy = CV->getType()->getElementType();
244 const Type *DstEltTy = DestVTy->getElementType();
246 // Otherwise, we're changing the number of elements in a vector, which
247 // requires endianness information to do the right thing. For example,
248 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
249 // folds to (little endian):
250 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
251 // and to (big endian):
252 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
254 // First thing is first. We only want to think about integer here, so if
255 // we have something in FP form, recast it as integer.
256 if (DstEltTy->isFloatingPoint()) {
257 // Fold to an vector of integers with same size as our FP type.
258 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
259 const Type *DestIVTy = VectorType::get(
260 IntegerType::get(Context, FPWidth), NumDstElt);
261 // Recursively handle this integer conversion, if possible.
262 C = FoldBitCast(C, DestIVTy, TD, Context);
265 // Finally, VMCore can handle this now that #elts line up.
266 return ConstantExpr::getBitCast(C, DestTy);
269 // Okay, we know the destination is integer, if the input is FP, convert
270 // it to integer first.
271 if (SrcEltTy->isFloatingPoint()) {
272 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
273 const Type *SrcIVTy = VectorType::get(
274 IntegerType::get(Context, FPWidth), NumSrcElt);
275 // Ask VMCore to do the conversion now that #elts line up.
276 C = ConstantExpr::getBitCast(C, SrcIVTy);
277 CV = dyn_cast<ConstantVector>(C);
278 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
281 // Now we know that the input and output vectors are both integer vectors
282 // of the same size, and that their #elements is not the same. Do the
283 // conversion here, which depends on whether the input or output has
285 bool isLittleEndian = TD.isLittleEndian();
287 SmallVector<Constant*, 32> Result;
288 if (NumDstElt < NumSrcElt) {
289 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
290 Constant *Zero = Constant::getNullValue(DstEltTy);
291 unsigned Ratio = NumSrcElt/NumDstElt;
292 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
294 for (unsigned i = 0; i != NumDstElt; ++i) {
295 // Build each element of the result.
296 Constant *Elt = Zero;
297 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
298 for (unsigned j = 0; j != Ratio; ++j) {
299 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
300 if (!Src) return 0; // Reject constantexpr elements.
302 // Zero extend the element to the right size.
303 Src = ConstantExpr::getZExt(Src, Elt->getType());
305 // Shift it to the right place, depending on endianness.
306 Src = ConstantExpr::getShl(Src,
307 ConstantInt::get(Src->getType(), ShiftAmt));
308 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
311 Elt = ConstantExpr::getOr(Elt, Src);
313 Result.push_back(Elt);
316 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
317 unsigned Ratio = NumDstElt/NumSrcElt;
318 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
320 // Loop over each source value, expanding into multiple results.
321 for (unsigned i = 0; i != NumSrcElt; ++i) {
322 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
323 if (!Src) return 0; // Reject constantexpr elements.
325 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
326 for (unsigned j = 0; j != Ratio; ++j) {
327 // Shift the piece of the value into the right place, depending on
329 Constant *Elt = ConstantExpr::getLShr(Src,
330 ConstantInt::get(Src->getType(), ShiftAmt));
331 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
333 // Truncate and remember this piece.
334 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
339 return ConstantVector::get(Result.data(), Result.size());
347 //===----------------------------------------------------------------------===//
348 // Constant Folding public APIs
349 //===----------------------------------------------------------------------===//
352 /// ConstantFoldInstruction - Attempt to constant fold the specified
353 /// instruction. If successful, the constant result is returned, if not, null
354 /// is returned. Note that this function can only fail when attempting to fold
355 /// instructions like loads and stores, which have no constant expression form.
357 Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
358 const TargetData *TD) {
359 if (PHINode *PN = dyn_cast<PHINode>(I)) {
360 if (PN->getNumIncomingValues() == 0)
361 return UndefValue::get(PN->getType());
363 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
364 if (Result == 0) return 0;
366 // Handle PHI nodes specially here...
367 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
368 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
369 return 0; // Not all the same incoming constants...
371 // If we reach here, all incoming values are the same constant.
375 // Scan the operand list, checking to see if they are all constants, if so,
376 // hand off to ConstantFoldInstOperands.
377 SmallVector<Constant*, 8> Ops;
378 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
379 if (Constant *Op = dyn_cast<Constant>(*i))
382 return 0; // All operands not constant!
384 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
385 return ConstantFoldCompareInstOperands(CI->getPredicate(),
386 Ops.data(), Ops.size(),
389 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
390 Ops.data(), Ops.size(), Context, TD);
393 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
394 /// using the specified TargetData. If successful, the constant result is
395 /// result is returned, if not, null is returned.
396 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
397 LLVMContext &Context,
398 const TargetData *TD) {
399 SmallVector<Constant*, 8> Ops;
400 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
401 Ops.push_back(cast<Constant>(*i));
404 return ConstantFoldCompareInstOperands(CE->getPredicate(),
405 Ops.data(), Ops.size(),
408 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
409 Ops.data(), Ops.size(), Context, TD);
412 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
413 /// specified opcode and operands. If successful, the constant result is
414 /// returned, if not, null is returned. Note that this function can fail when
415 /// attempting to fold instructions like loads and stores, which have no
416 /// constant expression form.
418 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
419 Constant* const* Ops, unsigned NumOps,
420 LLVMContext &Context,
421 const TargetData *TD) {
422 // Handle easy binops first.
423 if (Instruction::isBinaryOp(Opcode)) {
424 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
425 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
429 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
434 case Instruction::Call:
435 if (Function *F = dyn_cast<Function>(Ops[0]))
436 if (canConstantFoldCallTo(F))
437 return ConstantFoldCall(F, Ops+1, NumOps-1);
439 case Instruction::ICmp:
440 case Instruction::FCmp:
441 llvm_unreachable("This function is invalid for compares: no predicate specified");
442 case Instruction::PtrToInt:
443 // If the input is a inttoptr, eliminate the pair. This requires knowing
444 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
445 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
446 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
447 Constant *Input = CE->getOperand(0);
448 unsigned InWidth = Input->getType()->getScalarSizeInBits();
449 if (TD->getPointerSizeInBits() < InWidth) {
451 ConstantInt::get(Context, APInt::getLowBitsSet(InWidth,
452 TD->getPointerSizeInBits()));
453 Input = ConstantExpr::getAnd(Input, Mask);
455 // Do a zext or trunc to get to the dest size.
456 return ConstantExpr::getIntegerCast(Input, DestTy, false);
459 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
460 case Instruction::IntToPtr:
461 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
462 // the int size is >= the ptr size. This requires knowing the width of a
463 // pointer, so it can't be done in ConstantExpr::getCast.
464 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
466 TD->getPointerSizeInBits() <=
467 CE->getType()->getScalarSizeInBits()) {
468 if (CE->getOpcode() == Instruction::PtrToInt) {
469 Constant *Input = CE->getOperand(0);
470 Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
471 return C ? C : ConstantExpr::getBitCast(Input, DestTy);
473 // If there's a constant offset added to the integer value before
474 // it is casted back to a pointer, see if the expression can be
475 // converted into a GEP.
476 if (CE->getOpcode() == Instruction::Add)
477 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
478 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
479 if (R->getOpcode() == Instruction::PtrToInt)
480 if (GlobalVariable *GV =
481 dyn_cast<GlobalVariable>(R->getOperand(0))) {
482 const PointerType *GVTy = cast<PointerType>(GV->getType());
483 if (const ArrayType *AT =
484 dyn_cast<ArrayType>(GVTy->getElementType())) {
485 const Type *ElTy = AT->getElementType();
486 uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
487 APInt PSA(L->getValue().getBitWidth(), AllocSize);
488 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
489 L->getValue().urem(PSA) == 0) {
490 APInt ElemIdx = L->getValue().udiv(PSA);
491 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
492 AT->getNumElements()))) {
493 Constant *Index[] = {
494 Constant::getNullValue(CE->getType()),
495 ConstantInt::get(Context, ElemIdx)
498 ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
505 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
506 case Instruction::Trunc:
507 case Instruction::ZExt:
508 case Instruction::SExt:
509 case Instruction::FPTrunc:
510 case Instruction::FPExt:
511 case Instruction::UIToFP:
512 case Instruction::SIToFP:
513 case Instruction::FPToUI:
514 case Instruction::FPToSI:
515 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
516 case Instruction::BitCast:
518 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
520 return ConstantExpr::getBitCast(Ops[0], DestTy);
521 case Instruction::Select:
522 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
523 case Instruction::ExtractElement:
524 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
525 case Instruction::InsertElement:
526 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
527 case Instruction::ShuffleVector:
528 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
529 case Instruction::GetElementPtr:
530 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
533 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
537 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
538 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
539 /// returns a constant expression of the specified operands.
541 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
542 Constant*const * Ops,
544 LLVMContext &Context,
545 const TargetData *TD) {
546 // fold: icmp (inttoptr x), null -> icmp x, 0
547 // fold: icmp (ptrtoint x), 0 -> icmp x, null
548 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
549 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
551 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
552 // around to know if bit truncation is happening.
553 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
554 if (TD && Ops[1]->isNullValue()) {
555 const Type *IntPtrTy = TD->getIntPtrType(Context);
556 if (CE0->getOpcode() == Instruction::IntToPtr) {
557 // Convert the integer value to the right size to ensure we get the
558 // proper extension or truncation.
559 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
561 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
562 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
566 // Only do this transformation if the int is intptrty in size, otherwise
567 // there is a truncation or extension that we aren't modeling.
568 if (CE0->getOpcode() == Instruction::PtrToInt &&
569 CE0->getType() == IntPtrTy) {
570 Constant *C = CE0->getOperand(0);
571 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
573 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
578 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
579 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
580 const Type *IntPtrTy = TD->getIntPtrType(Context);
582 if (CE0->getOpcode() == Instruction::IntToPtr) {
583 // Convert the integer value to the right size to ensure we get the
584 // proper extension or truncation.
585 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
587 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
589 Constant *NewOps[] = { C0, C1 };
590 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
594 // Only do this transformation if the int is intptrty in size, otherwise
595 // there is a truncation or extension that we aren't modeling.
596 if ((CE0->getOpcode() == Instruction::PtrToInt &&
597 CE0->getType() == IntPtrTy &&
598 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
599 Constant *NewOps[] = {
600 CE0->getOperand(0), CE1->getOperand(0)
602 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
608 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
612 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
613 /// getelementptr constantexpr, return the constant value being addressed by the
614 /// constant expression, or null if something is funny and we can't decide.
615 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
617 LLVMContext &Context) {
618 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
619 return 0; // Do not allow stepping over the value!
621 // Loop over all of the operands, tracking down which value we are
623 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
624 for (++I; I != E; ++I)
625 if (const StructType *STy = dyn_cast<StructType>(*I)) {
626 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
627 assert(CU->getZExtValue() < STy->getNumElements() &&
628 "Struct index out of range!");
629 unsigned El = (unsigned)CU->getZExtValue();
630 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
631 C = CS->getOperand(El);
632 } else if (isa<ConstantAggregateZero>(C)) {
633 C = Constant::getNullValue(STy->getElementType(El));
634 } else if (isa<UndefValue>(C)) {
635 C = UndefValue::get(STy->getElementType(El));
639 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
640 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
641 if (CI->getZExtValue() >= ATy->getNumElements())
643 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
644 C = CA->getOperand(CI->getZExtValue());
645 else if (isa<ConstantAggregateZero>(C))
646 C = Constant::getNullValue(ATy->getElementType());
647 else if (isa<UndefValue>(C))
648 C = UndefValue::get(ATy->getElementType());
651 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
652 if (CI->getZExtValue() >= PTy->getNumElements())
654 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
655 C = CP->getOperand(CI->getZExtValue());
656 else if (isa<ConstantAggregateZero>(C))
657 C = Constant::getNullValue(PTy->getElementType());
658 else if (isa<UndefValue>(C))
659 C = UndefValue::get(PTy->getElementType());
672 //===----------------------------------------------------------------------===//
673 // Constant Folding for Calls
676 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
677 /// the specified function.
679 llvm::canConstantFoldCallTo(const Function *F) {
680 switch (F->getIntrinsicID()) {
681 case Intrinsic::sqrt:
682 case Intrinsic::powi:
683 case Intrinsic::bswap:
684 case Intrinsic::ctpop:
685 case Intrinsic::ctlz:
686 case Intrinsic::cttz:
691 if (!F->hasName()) return false;
692 StringRef Name = F->getName();
694 // In these cases, the check of the length is required. We don't want to
695 // return true for a name like "cos\0blah" which strcmp would return equal to
696 // "cos", but has length 8.
698 default: return false;
700 return Name == "acos" || Name == "asin" ||
701 Name == "atan" || Name == "atan2";
703 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
705 return Name == "exp";
707 return Name == "fabs" || Name == "fmod" || Name == "floor";
709 return Name == "log" || Name == "log10";
711 return Name == "pow";
713 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
714 Name == "sinf" || Name == "sqrtf";
716 return Name == "tan" || Name == "tanh";
720 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
721 const Type *Ty, LLVMContext &Context) {
729 if (Ty == Type::getFloatTy(Context))
730 return ConstantFP::get(Context, APFloat((float)V));
731 if (Ty == Type::getDoubleTy(Context))
732 return ConstantFP::get(Context, APFloat(V));
733 llvm_unreachable("Can only constant fold float/double");
734 return 0; // dummy return to suppress warning
737 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
740 LLVMContext &Context) {
748 if (Ty == Type::getFloatTy(Context))
749 return ConstantFP::get(Context, APFloat((float)V));
750 if (Ty == Type::getDoubleTy(Context))
751 return ConstantFP::get(Context, APFloat(V));
752 llvm_unreachable("Can only constant fold float/double");
753 return 0; // dummy return to suppress warning
756 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
757 /// with the specified arguments, returning null if unsuccessful.
760 llvm::ConstantFoldCall(Function *F,
761 Constant* const* Operands, unsigned NumOperands) {
762 if (!F->hasName()) return 0;
763 LLVMContext &Context = F->getContext();
764 StringRef Name = F->getName();
766 const Type *Ty = F->getReturnType();
767 if (NumOperands == 1) {
768 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
769 if (Ty!=Type::getFloatTy(F->getContext()) &&
770 Ty!=Type::getDoubleTy(Context))
772 /// Currently APFloat versions of these functions do not exist, so we use
773 /// the host native double versions. Float versions are not called
774 /// directly but for all these it is true (float)(f((double)arg)) ==
775 /// f(arg). Long double not supported yet.
776 double V = Ty==Type::getFloatTy(F->getContext()) ?
777 (double)Op->getValueAPF().convertToFloat():
778 Op->getValueAPF().convertToDouble();
782 return ConstantFoldFP(acos, V, Ty, Context);
783 else if (Name == "asin")
784 return ConstantFoldFP(asin, V, Ty, Context);
785 else if (Name == "atan")
786 return ConstantFoldFP(atan, V, Ty, Context);
790 return ConstantFoldFP(ceil, V, Ty, Context);
791 else if (Name == "cos")
792 return ConstantFoldFP(cos, V, Ty, Context);
793 else if (Name == "cosh")
794 return ConstantFoldFP(cosh, V, Ty, Context);
795 else if (Name == "cosf")
796 return ConstantFoldFP(cos, V, Ty, Context);
800 return ConstantFoldFP(exp, V, Ty, Context);
804 return ConstantFoldFP(fabs, V, Ty, Context);
805 else if (Name == "floor")
806 return ConstantFoldFP(floor, V, Ty, Context);
809 if (Name == "log" && V > 0)
810 return ConstantFoldFP(log, V, Ty, Context);
811 else if (Name == "log10" && V > 0)
812 return ConstantFoldFP(log10, V, Ty, Context);
813 else if (Name == "llvm.sqrt.f32" ||
814 Name == "llvm.sqrt.f64") {
816 return ConstantFoldFP(sqrt, V, Ty, Context);
818 return Constant::getNullValue(Ty);
823 return ConstantFoldFP(sin, V, Ty, Context);
824 else if (Name == "sinh")
825 return ConstantFoldFP(sinh, V, Ty, Context);
826 else if (Name == "sqrt" && V >= 0)
827 return ConstantFoldFP(sqrt, V, Ty, Context);
828 else if (Name == "sqrtf" && V >= 0)
829 return ConstantFoldFP(sqrt, V, Ty, Context);
830 else if (Name == "sinf")
831 return ConstantFoldFP(sin, V, Ty, Context);
835 return ConstantFoldFP(tan, V, Ty, Context);
836 else if (Name == "tanh")
837 return ConstantFoldFP(tanh, V, Ty, Context);
842 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
843 if (Name.startswith("llvm.bswap"))
844 return ConstantInt::get(Context, Op->getValue().byteSwap());
845 else if (Name.startswith("llvm.ctpop"))
846 return ConstantInt::get(Ty, Op->getValue().countPopulation());
847 else if (Name.startswith("llvm.cttz"))
848 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
849 else if (Name.startswith("llvm.ctlz"))
850 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
852 } else if (NumOperands == 2) {
853 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
854 if (Ty!=Type::getFloatTy(F->getContext()) &&
855 Ty!=Type::getDoubleTy(Context))
857 double Op1V = Ty==Type::getFloatTy(F->getContext()) ?
858 (double)Op1->getValueAPF().convertToFloat():
859 Op1->getValueAPF().convertToDouble();
860 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
861 double Op2V = Ty==Type::getFloatTy(F->getContext()) ?
862 (double)Op2->getValueAPF().convertToFloat():
863 Op2->getValueAPF().convertToDouble();
866 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context);
867 } else if (Name == "fmod") {
868 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context);
869 } else if (Name == "atan2") {
870 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context);
872 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
873 if (Name == "llvm.powi.f32") {
874 return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V,
875 (int)Op2C->getZExtValue())));
876 } else if (Name == "llvm.powi.f64") {
877 return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V,
878 (int)Op2C->getZExtValue())));