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 uint64_t BasePtr = 0;
134 bool BaseIsInt = true;
135 if (!Ptr->isNullValue()) {
136 // If this is a inttoptr from a constant int, we can fold this as the base,
137 // otherwise we can't.
138 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
139 if (CE->getOpcode() == Instruction::IntToPtr)
140 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
141 BasePtr = Base->getZExtValue();
147 // If this is a constant expr gep that is effectively computing an
148 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
149 for (unsigned i = 1; i != NumOps; ++i)
150 if (!isa<ConstantInt>(Ops[i]))
153 uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
154 (Value**)Ops+1, NumOps-1);
155 // If the base value for this address is a literal integer value, fold the
156 // getelementptr to the resulting integer value casted to the pointer type.
158 Constant *C = ConstantInt::get(TD->getIntPtrType(Context), Offset+BasePtr);
159 return ConstantExpr::getIntToPtr(C, ResultTy);
162 // Otherwise form a regular getelementptr. Recompute the indices so that
163 // we eliminate over-indexing of the notional static type array bounds.
164 // This makes it easy to determine if the getelementptr is "inbounds".
165 // Also, this helps GlobalOpt do SROA on GlobalVariables.
166 const Type *Ty = Ptr->getType();
167 SmallVector<Constant*, 32> NewIdxs;
168 for (unsigned Index = 1; Index != NumOps; ++Index) {
169 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
170 // Determine which element of the array the offset points into.
171 uint64_t ElemSize = TD->getTypeAllocSize(ATy->getElementType());
174 uint64_t NewIdx = Offset / ElemSize;
175 Offset -= NewIdx * ElemSize;
176 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx));
177 Ty = ATy->getElementType();
178 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
179 // Determine which field of the struct the offset points into.
180 const StructLayout &SL = *TD->getStructLayout(STy);
181 unsigned ElIdx = SL.getElementContainingOffset(Offset);
182 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx));
183 Offset -= SL.getElementOffset(ElIdx);
184 Ty = STy->getTypeAtIndex(ElIdx);
190 // If the base is the start of a GlobalVariable and all the array indices
191 // remain in their static bounds, the GEP is inbounds. We can check that
192 // all indices are in bounds by just checking the first index only
193 // because we've just normalized all the indices.
194 if (isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue())
195 return ConstantExpr::getInBoundsGetElementPtr(Ptr,
196 &NewIdxs[0], NewIdxs.size());
198 // Otherwise it may not be inbounds.
199 return ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
202 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
203 /// targetdata. Return 0 if unfoldable.
204 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
205 const TargetData &TD, LLVMContext &Context) {
206 // If this is a bitcast from constant vector -> vector, fold it.
207 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
208 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
209 // If the element types match, VMCore can fold it.
210 unsigned NumDstElt = DestVTy->getNumElements();
211 unsigned NumSrcElt = CV->getNumOperands();
212 if (NumDstElt == NumSrcElt)
215 const Type *SrcEltTy = CV->getType()->getElementType();
216 const Type *DstEltTy = DestVTy->getElementType();
218 // Otherwise, we're changing the number of elements in a vector, which
219 // requires endianness information to do the right thing. For example,
220 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
221 // folds to (little endian):
222 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
223 // and to (big endian):
224 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
226 // First thing is first. We only want to think about integer here, so if
227 // we have something in FP form, recast it as integer.
228 if (DstEltTy->isFloatingPoint()) {
229 // Fold to an vector of integers with same size as our FP type.
230 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
231 const Type *DestIVTy = VectorType::get(
232 IntegerType::get(Context, FPWidth), NumDstElt);
233 // Recursively handle this integer conversion, if possible.
234 C = FoldBitCast(C, DestIVTy, TD, Context);
237 // Finally, VMCore can handle this now that #elts line up.
238 return ConstantExpr::getBitCast(C, DestTy);
241 // Okay, we know the destination is integer, if the input is FP, convert
242 // it to integer first.
243 if (SrcEltTy->isFloatingPoint()) {
244 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
245 const Type *SrcIVTy = VectorType::get(
246 IntegerType::get(Context, FPWidth), NumSrcElt);
247 // Ask VMCore to do the conversion now that #elts line up.
248 C = ConstantExpr::getBitCast(C, SrcIVTy);
249 CV = dyn_cast<ConstantVector>(C);
250 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
253 // Now we know that the input and output vectors are both integer vectors
254 // of the same size, and that their #elements is not the same. Do the
255 // conversion here, which depends on whether the input or output has
257 bool isLittleEndian = TD.isLittleEndian();
259 SmallVector<Constant*, 32> Result;
260 if (NumDstElt < NumSrcElt) {
261 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
262 Constant *Zero = Constant::getNullValue(DstEltTy);
263 unsigned Ratio = NumSrcElt/NumDstElt;
264 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
266 for (unsigned i = 0; i != NumDstElt; ++i) {
267 // Build each element of the result.
268 Constant *Elt = Zero;
269 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
270 for (unsigned j = 0; j != Ratio; ++j) {
271 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
272 if (!Src) return 0; // Reject constantexpr elements.
274 // Zero extend the element to the right size.
275 Src = ConstantExpr::getZExt(Src, Elt->getType());
277 // Shift it to the right place, depending on endianness.
278 Src = ConstantExpr::getShl(Src,
279 ConstantInt::get(Src->getType(), ShiftAmt));
280 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
283 Elt = ConstantExpr::getOr(Elt, Src);
285 Result.push_back(Elt);
288 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
289 unsigned Ratio = NumDstElt/NumSrcElt;
290 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
292 // Loop over each source value, expanding into multiple results.
293 for (unsigned i = 0; i != NumSrcElt; ++i) {
294 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
295 if (!Src) return 0; // Reject constantexpr elements.
297 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
298 for (unsigned j = 0; j != Ratio; ++j) {
299 // Shift the piece of the value into the right place, depending on
301 Constant *Elt = ConstantExpr::getLShr(Src,
302 ConstantInt::get(Src->getType(), ShiftAmt));
303 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
305 // Truncate and remember this piece.
306 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
311 return ConstantVector::get(Result.data(), Result.size());
319 //===----------------------------------------------------------------------===//
320 // Constant Folding public APIs
321 //===----------------------------------------------------------------------===//
324 /// ConstantFoldInstruction - Attempt to constant fold the specified
325 /// instruction. If successful, the constant result is returned, if not, null
326 /// is returned. Note that this function can only fail when attempting to fold
327 /// instructions like loads and stores, which have no constant expression form.
329 Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
330 const TargetData *TD) {
331 if (PHINode *PN = dyn_cast<PHINode>(I)) {
332 if (PN->getNumIncomingValues() == 0)
333 return UndefValue::get(PN->getType());
335 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
336 if (Result == 0) return 0;
338 // Handle PHI nodes specially here...
339 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
340 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
341 return 0; // Not all the same incoming constants...
343 // If we reach here, all incoming values are the same constant.
347 // Scan the operand list, checking to see if they are all constants, if so,
348 // hand off to ConstantFoldInstOperands.
349 SmallVector<Constant*, 8> Ops;
350 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
351 if (Constant *Op = dyn_cast<Constant>(*i))
354 return 0; // All operands not constant!
356 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
357 return ConstantFoldCompareInstOperands(CI->getPredicate(),
358 Ops.data(), Ops.size(),
361 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
362 Ops.data(), Ops.size(), Context, TD);
365 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
366 /// using the specified TargetData. If successful, the constant result is
367 /// result is returned, if not, null is returned.
368 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
369 LLVMContext &Context,
370 const TargetData *TD) {
371 SmallVector<Constant*, 8> Ops;
372 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
373 Ops.push_back(cast<Constant>(*i));
376 return ConstantFoldCompareInstOperands(CE->getPredicate(),
377 Ops.data(), Ops.size(),
380 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
381 Ops.data(), Ops.size(), Context, TD);
384 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
385 /// specified opcode and operands. If successful, the constant result is
386 /// returned, if not, null is returned. Note that this function can fail when
387 /// attempting to fold instructions like loads and stores, which have no
388 /// constant expression form.
390 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
391 Constant* const* Ops, unsigned NumOps,
392 LLVMContext &Context,
393 const TargetData *TD) {
394 // Handle easy binops first.
395 if (Instruction::isBinaryOp(Opcode)) {
396 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
397 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
401 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
406 case Instruction::Call:
407 if (Function *F = dyn_cast<Function>(Ops[0]))
408 if (canConstantFoldCallTo(F))
409 return ConstantFoldCall(F, Ops+1, NumOps-1);
411 case Instruction::ICmp:
412 case Instruction::FCmp:
413 llvm_unreachable("This function is invalid for compares: no predicate specified");
414 case Instruction::PtrToInt:
415 // If the input is a inttoptr, eliminate the pair. This requires knowing
416 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
417 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
418 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
419 Constant *Input = CE->getOperand(0);
420 unsigned InWidth = Input->getType()->getScalarSizeInBits();
421 if (TD->getPointerSizeInBits() < InWidth) {
423 ConstantInt::get(Context, APInt::getLowBitsSet(InWidth,
424 TD->getPointerSizeInBits()));
425 Input = ConstantExpr::getAnd(Input, Mask);
427 // Do a zext or trunc to get to the dest size.
428 return ConstantExpr::getIntegerCast(Input, DestTy, false);
431 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
432 case Instruction::IntToPtr:
433 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
434 // the int size is >= the ptr size. This requires knowing the width of a
435 // pointer, so it can't be done in ConstantExpr::getCast.
436 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
438 TD->getPointerSizeInBits() <=
439 CE->getType()->getScalarSizeInBits()) {
440 if (CE->getOpcode() == Instruction::PtrToInt) {
441 Constant *Input = CE->getOperand(0);
442 Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
443 return C ? C : ConstantExpr::getBitCast(Input, DestTy);
445 // If there's a constant offset added to the integer value before
446 // it is casted back to a pointer, see if the expression can be
447 // converted into a GEP.
448 if (CE->getOpcode() == Instruction::Add)
449 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
450 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
451 if (R->getOpcode() == Instruction::PtrToInt)
452 if (GlobalVariable *GV =
453 dyn_cast<GlobalVariable>(R->getOperand(0))) {
454 const PointerType *GVTy = cast<PointerType>(GV->getType());
455 if (const ArrayType *AT =
456 dyn_cast<ArrayType>(GVTy->getElementType())) {
457 const Type *ElTy = AT->getElementType();
458 uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
459 APInt PSA(L->getValue().getBitWidth(), AllocSize);
460 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
461 L->getValue().urem(PSA) == 0) {
462 APInt ElemIdx = L->getValue().udiv(PSA);
463 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
464 AT->getNumElements()))) {
465 Constant *Index[] = {
466 Constant::getNullValue(CE->getType()),
467 ConstantInt::get(Context, ElemIdx)
470 ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
477 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
478 case Instruction::Trunc:
479 case Instruction::ZExt:
480 case Instruction::SExt:
481 case Instruction::FPTrunc:
482 case Instruction::FPExt:
483 case Instruction::UIToFP:
484 case Instruction::SIToFP:
485 case Instruction::FPToUI:
486 case Instruction::FPToSI:
487 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
488 case Instruction::BitCast:
490 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
492 return ConstantExpr::getBitCast(Ops[0], DestTy);
493 case Instruction::Select:
494 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
495 case Instruction::ExtractElement:
496 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
497 case Instruction::InsertElement:
498 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
499 case Instruction::ShuffleVector:
500 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
501 case Instruction::GetElementPtr:
502 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
505 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
509 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
510 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
511 /// returns a constant expression of the specified operands.
513 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
514 Constant*const * Ops,
516 LLVMContext &Context,
517 const TargetData *TD) {
518 // fold: icmp (inttoptr x), null -> icmp x, 0
519 // fold: icmp (ptrtoint x), 0 -> icmp x, null
520 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
521 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
523 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
524 // around to know if bit truncation is happening.
525 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
526 if (TD && Ops[1]->isNullValue()) {
527 const Type *IntPtrTy = TD->getIntPtrType(Context);
528 if (CE0->getOpcode() == Instruction::IntToPtr) {
529 // Convert the integer value to the right size to ensure we get the
530 // proper extension or truncation.
531 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
533 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
534 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
538 // Only do this transformation if the int is intptrty in size, otherwise
539 // there is a truncation or extension that we aren't modeling.
540 if (CE0->getOpcode() == Instruction::PtrToInt &&
541 CE0->getType() == IntPtrTy) {
542 Constant *C = CE0->getOperand(0);
543 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
545 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
550 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
551 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
552 const Type *IntPtrTy = TD->getIntPtrType(Context);
554 if (CE0->getOpcode() == Instruction::IntToPtr) {
555 // Convert the integer value to the right size to ensure we get the
556 // proper extension or truncation.
557 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
559 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
561 Constant *NewOps[] = { C0, C1 };
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 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
571 Constant *NewOps[] = {
572 CE0->getOperand(0), CE1->getOperand(0)
574 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
580 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
584 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
585 /// getelementptr constantexpr, return the constant value being addressed by the
586 /// constant expression, or null if something is funny and we can't decide.
587 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
589 LLVMContext &Context) {
590 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
591 return 0; // Do not allow stepping over the value!
593 // Loop over all of the operands, tracking down which value we are
595 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
596 for (++I; I != E; ++I)
597 if (const StructType *STy = dyn_cast<StructType>(*I)) {
598 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
599 assert(CU->getZExtValue() < STy->getNumElements() &&
600 "Struct index out of range!");
601 unsigned El = (unsigned)CU->getZExtValue();
602 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
603 C = CS->getOperand(El);
604 } else if (isa<ConstantAggregateZero>(C)) {
605 C = Constant::getNullValue(STy->getElementType(El));
606 } else if (isa<UndefValue>(C)) {
607 C = UndefValue::get(STy->getElementType(El));
611 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
612 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
613 if (CI->getZExtValue() >= ATy->getNumElements())
615 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
616 C = CA->getOperand(CI->getZExtValue());
617 else if (isa<ConstantAggregateZero>(C))
618 C = Constant::getNullValue(ATy->getElementType());
619 else if (isa<UndefValue>(C))
620 C = UndefValue::get(ATy->getElementType());
623 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
624 if (CI->getZExtValue() >= PTy->getNumElements())
626 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
627 C = CP->getOperand(CI->getZExtValue());
628 else if (isa<ConstantAggregateZero>(C))
629 C = Constant::getNullValue(PTy->getElementType());
630 else if (isa<UndefValue>(C))
631 C = UndefValue::get(PTy->getElementType());
644 //===----------------------------------------------------------------------===//
645 // Constant Folding for Calls
648 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
649 /// the specified function.
651 llvm::canConstantFoldCallTo(const Function *F) {
652 switch (F->getIntrinsicID()) {
653 case Intrinsic::sqrt:
654 case Intrinsic::powi:
655 case Intrinsic::bswap:
656 case Intrinsic::ctpop:
657 case Intrinsic::ctlz:
658 case Intrinsic::cttz:
663 if (!F->hasName()) return false;
664 StringRef Name = F->getName();
666 // In these cases, the check of the length is required. We don't want to
667 // return true for a name like "cos\0blah" which strcmp would return equal to
668 // "cos", but has length 8.
670 default: return false;
672 return Name == "acos" || Name == "asin" ||
673 Name == "atan" || Name == "atan2";
675 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
677 return Name == "exp";
679 return Name == "fabs" || Name == "fmod" || Name == "floor";
681 return Name == "log" || Name == "log10";
683 return Name == "pow";
685 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
686 Name == "sinf" || Name == "sqrtf";
688 return Name == "tan" || Name == "tanh";
692 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
693 const Type *Ty, LLVMContext &Context) {
701 if (Ty == Type::getFloatTy(Context))
702 return ConstantFP::get(Context, APFloat((float)V));
703 if (Ty == Type::getDoubleTy(Context))
704 return ConstantFP::get(Context, APFloat(V));
705 llvm_unreachable("Can only constant fold float/double");
706 return 0; // dummy return to suppress warning
709 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
712 LLVMContext &Context) {
720 if (Ty == Type::getFloatTy(Context))
721 return ConstantFP::get(Context, APFloat((float)V));
722 if (Ty == Type::getDoubleTy(Context))
723 return ConstantFP::get(Context, APFloat(V));
724 llvm_unreachable("Can only constant fold float/double");
725 return 0; // dummy return to suppress warning
728 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
729 /// with the specified arguments, returning null if unsuccessful.
732 llvm::ConstantFoldCall(Function *F,
733 Constant* const* Operands, unsigned NumOperands) {
734 if (!F->hasName()) return 0;
735 LLVMContext &Context = F->getContext();
736 StringRef Name = F->getName();
738 const Type *Ty = F->getReturnType();
739 if (NumOperands == 1) {
740 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
741 if (Ty!=Type::getFloatTy(F->getContext()) &&
742 Ty!=Type::getDoubleTy(Context))
744 /// Currently APFloat versions of these functions do not exist, so we use
745 /// the host native double versions. Float versions are not called
746 /// directly but for all these it is true (float)(f((double)arg)) ==
747 /// f(arg). Long double not supported yet.
748 double V = Ty==Type::getFloatTy(F->getContext()) ?
749 (double)Op->getValueAPF().convertToFloat():
750 Op->getValueAPF().convertToDouble();
754 return ConstantFoldFP(acos, V, Ty, Context);
755 else if (Name == "asin")
756 return ConstantFoldFP(asin, V, Ty, Context);
757 else if (Name == "atan")
758 return ConstantFoldFP(atan, V, Ty, Context);
762 return ConstantFoldFP(ceil, V, Ty, Context);
763 else if (Name == "cos")
764 return ConstantFoldFP(cos, V, Ty, Context);
765 else if (Name == "cosh")
766 return ConstantFoldFP(cosh, V, Ty, Context);
767 else if (Name == "cosf")
768 return ConstantFoldFP(cos, V, Ty, Context);
772 return ConstantFoldFP(exp, V, Ty, Context);
776 return ConstantFoldFP(fabs, V, Ty, Context);
777 else if (Name == "floor")
778 return ConstantFoldFP(floor, V, Ty, Context);
781 if (Name == "log" && V > 0)
782 return ConstantFoldFP(log, V, Ty, Context);
783 else if (Name == "log10" && V > 0)
784 return ConstantFoldFP(log10, V, Ty, Context);
785 else if (Name == "llvm.sqrt.f32" ||
786 Name == "llvm.sqrt.f64") {
788 return ConstantFoldFP(sqrt, V, Ty, Context);
790 return Constant::getNullValue(Ty);
795 return ConstantFoldFP(sin, V, Ty, Context);
796 else if (Name == "sinh")
797 return ConstantFoldFP(sinh, V, Ty, Context);
798 else if (Name == "sqrt" && V >= 0)
799 return ConstantFoldFP(sqrt, V, Ty, Context);
800 else if (Name == "sqrtf" && V >= 0)
801 return ConstantFoldFP(sqrt, V, Ty, Context);
802 else if (Name == "sinf")
803 return ConstantFoldFP(sin, V, Ty, Context);
807 return ConstantFoldFP(tan, V, Ty, Context);
808 else if (Name == "tanh")
809 return ConstantFoldFP(tanh, V, Ty, Context);
814 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
815 if (Name.startswith("llvm.bswap"))
816 return ConstantInt::get(Context, Op->getValue().byteSwap());
817 else if (Name.startswith("llvm.ctpop"))
818 return ConstantInt::get(Ty, Op->getValue().countPopulation());
819 else if (Name.startswith("llvm.cttz"))
820 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
821 else if (Name.startswith("llvm.ctlz"))
822 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
824 } else if (NumOperands == 2) {
825 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
826 if (Ty!=Type::getFloatTy(F->getContext()) &&
827 Ty!=Type::getDoubleTy(Context))
829 double Op1V = Ty==Type::getFloatTy(F->getContext()) ?
830 (double)Op1->getValueAPF().convertToFloat():
831 Op1->getValueAPF().convertToDouble();
832 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
833 double Op2V = Ty==Type::getFloatTy(F->getContext()) ?
834 (double)Op2->getValueAPF().convertToFloat():
835 Op2->getValueAPF().convertToDouble();
838 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context);
839 } else if (Name == "fmod") {
840 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context);
841 } else if (Name == "atan2") {
842 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context);
844 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
845 if (Name == "llvm.powi.f32") {
846 return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V,
847 (int)Op2C->getZExtValue())));
848 } else if (Name == "llvm.powi.f64") {
849 return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V,
850 (int)Op2C->getZExtValue())));