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;
169 if (const SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
170 // The only pointer indexing we'll do is on the first index of the GEP.
171 if (isa<PointerType>(ATy) && ATy != Ptr->getType())
173 // Determine which element of the array the offset points into.
174 uint64_t ElemSize = TD->getTypeAllocSize(ATy->getElementType());
177 uint64_t NewIdx = Offset / ElemSize;
178 Offset -= NewIdx * ElemSize;
179 NewIdxs.push_back(ConstantInt::get(TD->getIntPtrType(Context), NewIdx));
180 Ty = ATy->getElementType();
181 } else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
182 // Determine which field of the struct the offset points into.
183 const StructLayout &SL = *TD->getStructLayout(STy);
184 unsigned ElIdx = SL.getElementContainingOffset(Offset);
185 NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Context), ElIdx));
186 Offset -= SL.getElementOffset(ElIdx);
187 Ty = STy->getTypeAtIndex(ElIdx);
189 // We've reached some non-indexable type.
192 } while (Ty != cast<PointerType>(ResultTy)->getElementType());
194 // If we haven't used up the entire offset by descending the static
195 // type, then the offset is pointing into the middle of an indivisible
196 // member, so we can't simplify it.
200 // If the base is the start of a GlobalVariable and all the array indices
201 // remain in their static bounds, the GEP is inbounds. We can check that
202 // all indices are in bounds by just checking the first index only
203 // because we've just normalized all the indices.
204 Constant *C = isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue() ?
205 ConstantExpr::getInBoundsGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()) :
206 ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
207 assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
208 "Computed GetElementPtr has unexpected type!");
210 // If we ended up indexing a member with a type that doesn't match
211 // type type of what the original indices indexed, add a cast.
212 if (Ty != cast<PointerType>(ResultTy)->getElementType())
213 C = ConstantExpr::getBitCast(C, ResultTy);
218 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
219 /// targetdata. Return 0 if unfoldable.
220 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
221 const TargetData &TD, LLVMContext &Context) {
222 // If this is a bitcast from constant vector -> vector, fold it.
223 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
224 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
225 // If the element types match, VMCore can fold it.
226 unsigned NumDstElt = DestVTy->getNumElements();
227 unsigned NumSrcElt = CV->getNumOperands();
228 if (NumDstElt == NumSrcElt)
231 const Type *SrcEltTy = CV->getType()->getElementType();
232 const Type *DstEltTy = DestVTy->getElementType();
234 // Otherwise, we're changing the number of elements in a vector, which
235 // requires endianness information to do the right thing. For example,
236 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
237 // folds to (little endian):
238 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
239 // and to (big endian):
240 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
242 // First thing is first. We only want to think about integer here, so if
243 // we have something in FP form, recast it as integer.
244 if (DstEltTy->isFloatingPoint()) {
245 // Fold to an vector of integers with same size as our FP type.
246 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
247 const Type *DestIVTy = VectorType::get(
248 IntegerType::get(Context, FPWidth), NumDstElt);
249 // Recursively handle this integer conversion, if possible.
250 C = FoldBitCast(C, DestIVTy, TD, Context);
253 // Finally, VMCore can handle this now that #elts line up.
254 return ConstantExpr::getBitCast(C, DestTy);
257 // Okay, we know the destination is integer, if the input is FP, convert
258 // it to integer first.
259 if (SrcEltTy->isFloatingPoint()) {
260 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
261 const Type *SrcIVTy = VectorType::get(
262 IntegerType::get(Context, FPWidth), NumSrcElt);
263 // Ask VMCore to do the conversion now that #elts line up.
264 C = ConstantExpr::getBitCast(C, SrcIVTy);
265 CV = dyn_cast<ConstantVector>(C);
266 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
269 // Now we know that the input and output vectors are both integer vectors
270 // of the same size, and that their #elements is not the same. Do the
271 // conversion here, which depends on whether the input or output has
273 bool isLittleEndian = TD.isLittleEndian();
275 SmallVector<Constant*, 32> Result;
276 if (NumDstElt < NumSrcElt) {
277 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
278 Constant *Zero = Constant::getNullValue(DstEltTy);
279 unsigned Ratio = NumSrcElt/NumDstElt;
280 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
282 for (unsigned i = 0; i != NumDstElt; ++i) {
283 // Build each element of the result.
284 Constant *Elt = Zero;
285 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
286 for (unsigned j = 0; j != Ratio; ++j) {
287 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
288 if (!Src) return 0; // Reject constantexpr elements.
290 // Zero extend the element to the right size.
291 Src = ConstantExpr::getZExt(Src, Elt->getType());
293 // Shift it to the right place, depending on endianness.
294 Src = ConstantExpr::getShl(Src,
295 ConstantInt::get(Src->getType(), ShiftAmt));
296 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
299 Elt = ConstantExpr::getOr(Elt, Src);
301 Result.push_back(Elt);
304 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
305 unsigned Ratio = NumDstElt/NumSrcElt;
306 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
308 // Loop over each source value, expanding into multiple results.
309 for (unsigned i = 0; i != NumSrcElt; ++i) {
310 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
311 if (!Src) return 0; // Reject constantexpr elements.
313 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
314 for (unsigned j = 0; j != Ratio; ++j) {
315 // Shift the piece of the value into the right place, depending on
317 Constant *Elt = ConstantExpr::getLShr(Src,
318 ConstantInt::get(Src->getType(), ShiftAmt));
319 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
321 // Truncate and remember this piece.
322 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
327 return ConstantVector::get(Result.data(), Result.size());
335 //===----------------------------------------------------------------------===//
336 // Constant Folding public APIs
337 //===----------------------------------------------------------------------===//
340 /// ConstantFoldInstruction - Attempt to constant fold the specified
341 /// instruction. If successful, the constant result is returned, if not, null
342 /// is returned. Note that this function can only fail when attempting to fold
343 /// instructions like loads and stores, which have no constant expression form.
345 Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
346 const TargetData *TD) {
347 if (PHINode *PN = dyn_cast<PHINode>(I)) {
348 if (PN->getNumIncomingValues() == 0)
349 return UndefValue::get(PN->getType());
351 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
352 if (Result == 0) return 0;
354 // Handle PHI nodes specially here...
355 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
356 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
357 return 0; // Not all the same incoming constants...
359 // If we reach here, all incoming values are the same constant.
363 // Scan the operand list, checking to see if they are all constants, if so,
364 // hand off to ConstantFoldInstOperands.
365 SmallVector<Constant*, 8> Ops;
366 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
367 if (Constant *Op = dyn_cast<Constant>(*i))
370 return 0; // All operands not constant!
372 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
373 return ConstantFoldCompareInstOperands(CI->getPredicate(),
374 Ops.data(), Ops.size(),
377 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
378 Ops.data(), Ops.size(), Context, TD);
381 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
382 /// using the specified TargetData. If successful, the constant result is
383 /// result is returned, if not, null is returned.
384 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
385 LLVMContext &Context,
386 const TargetData *TD) {
387 SmallVector<Constant*, 8> Ops;
388 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
389 Ops.push_back(cast<Constant>(*i));
392 return ConstantFoldCompareInstOperands(CE->getPredicate(),
393 Ops.data(), Ops.size(),
396 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
397 Ops.data(), Ops.size(), Context, TD);
400 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
401 /// specified opcode and operands. If successful, the constant result is
402 /// returned, if not, null is returned. Note that this function can fail when
403 /// attempting to fold instructions like loads and stores, which have no
404 /// constant expression form.
406 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
407 Constant* const* Ops, unsigned NumOps,
408 LLVMContext &Context,
409 const TargetData *TD) {
410 // Handle easy binops first.
411 if (Instruction::isBinaryOp(Opcode)) {
412 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
413 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
417 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
422 case Instruction::Call:
423 if (Function *F = dyn_cast<Function>(Ops[0]))
424 if (canConstantFoldCallTo(F))
425 return ConstantFoldCall(F, Ops+1, NumOps-1);
427 case Instruction::ICmp:
428 case Instruction::FCmp:
429 llvm_unreachable("This function is invalid for compares: no predicate specified");
430 case Instruction::PtrToInt:
431 // If the input is a inttoptr, eliminate the pair. This requires knowing
432 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
433 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
434 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
435 Constant *Input = CE->getOperand(0);
436 unsigned InWidth = Input->getType()->getScalarSizeInBits();
437 if (TD->getPointerSizeInBits() < InWidth) {
439 ConstantInt::get(Context, APInt::getLowBitsSet(InWidth,
440 TD->getPointerSizeInBits()));
441 Input = ConstantExpr::getAnd(Input, Mask);
443 // Do a zext or trunc to get to the dest size.
444 return ConstantExpr::getIntegerCast(Input, DestTy, false);
447 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
448 case Instruction::IntToPtr:
449 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
450 // the int size is >= the ptr size. This requires knowing the width of a
451 // pointer, so it can't be done in ConstantExpr::getCast.
452 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
454 TD->getPointerSizeInBits() <=
455 CE->getType()->getScalarSizeInBits()) {
456 if (CE->getOpcode() == Instruction::PtrToInt) {
457 Constant *Input = CE->getOperand(0);
458 Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
459 return C ? C : ConstantExpr::getBitCast(Input, DestTy);
461 // If there's a constant offset added to the integer value before
462 // it is casted back to a pointer, see if the expression can be
463 // converted into a GEP.
464 if (CE->getOpcode() == Instruction::Add)
465 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
466 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
467 if (R->getOpcode() == Instruction::PtrToInt)
468 if (GlobalVariable *GV =
469 dyn_cast<GlobalVariable>(R->getOperand(0))) {
470 const PointerType *GVTy = cast<PointerType>(GV->getType());
471 if (const ArrayType *AT =
472 dyn_cast<ArrayType>(GVTy->getElementType())) {
473 const Type *ElTy = AT->getElementType();
474 uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
475 APInt PSA(L->getValue().getBitWidth(), AllocSize);
476 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
477 L->getValue().urem(PSA) == 0) {
478 APInt ElemIdx = L->getValue().udiv(PSA);
479 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
480 AT->getNumElements()))) {
481 Constant *Index[] = {
482 Constant::getNullValue(CE->getType()),
483 ConstantInt::get(Context, ElemIdx)
486 ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
493 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
494 case Instruction::Trunc:
495 case Instruction::ZExt:
496 case Instruction::SExt:
497 case Instruction::FPTrunc:
498 case Instruction::FPExt:
499 case Instruction::UIToFP:
500 case Instruction::SIToFP:
501 case Instruction::FPToUI:
502 case Instruction::FPToSI:
503 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
504 case Instruction::BitCast:
506 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
508 return ConstantExpr::getBitCast(Ops[0], DestTy);
509 case Instruction::Select:
510 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
511 case Instruction::ExtractElement:
512 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
513 case Instruction::InsertElement:
514 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
515 case Instruction::ShuffleVector:
516 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
517 case Instruction::GetElementPtr:
518 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
521 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
525 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
526 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
527 /// returns a constant expression of the specified operands.
529 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
530 Constant*const * Ops,
532 LLVMContext &Context,
533 const TargetData *TD) {
534 // fold: icmp (inttoptr x), null -> icmp x, 0
535 // fold: icmp (ptrtoint x), 0 -> icmp x, null
536 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
537 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
539 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
540 // around to know if bit truncation is happening.
541 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
542 if (TD && Ops[1]->isNullValue()) {
543 const Type *IntPtrTy = TD->getIntPtrType(Context);
544 if (CE0->getOpcode() == Instruction::IntToPtr) {
545 // Convert the integer value to the right size to ensure we get the
546 // proper extension or truncation.
547 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
549 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
550 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
554 // Only do this transformation if the int is intptrty in size, otherwise
555 // there is a truncation or extension that we aren't modeling.
556 if (CE0->getOpcode() == Instruction::PtrToInt &&
557 CE0->getType() == IntPtrTy) {
558 Constant *C = CE0->getOperand(0);
559 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
561 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
566 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
567 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
568 const Type *IntPtrTy = TD->getIntPtrType(Context);
570 if (CE0->getOpcode() == Instruction::IntToPtr) {
571 // Convert the integer value to the right size to ensure we get the
572 // proper extension or truncation.
573 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
575 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
577 Constant *NewOps[] = { C0, C1 };
578 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
582 // Only do this transformation if the int is intptrty in size, otherwise
583 // there is a truncation or extension that we aren't modeling.
584 if ((CE0->getOpcode() == Instruction::PtrToInt &&
585 CE0->getType() == IntPtrTy &&
586 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
587 Constant *NewOps[] = {
588 CE0->getOperand(0), CE1->getOperand(0)
590 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
596 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
600 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
601 /// getelementptr constantexpr, return the constant value being addressed by the
602 /// constant expression, or null if something is funny and we can't decide.
603 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
605 LLVMContext &Context) {
606 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
607 return 0; // Do not allow stepping over the value!
609 // Loop over all of the operands, tracking down which value we are
611 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
612 for (++I; I != E; ++I)
613 if (const StructType *STy = dyn_cast<StructType>(*I)) {
614 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
615 assert(CU->getZExtValue() < STy->getNumElements() &&
616 "Struct index out of range!");
617 unsigned El = (unsigned)CU->getZExtValue();
618 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
619 C = CS->getOperand(El);
620 } else if (isa<ConstantAggregateZero>(C)) {
621 C = Constant::getNullValue(STy->getElementType(El));
622 } else if (isa<UndefValue>(C)) {
623 C = UndefValue::get(STy->getElementType(El));
627 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
628 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
629 if (CI->getZExtValue() >= ATy->getNumElements())
631 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
632 C = CA->getOperand(CI->getZExtValue());
633 else if (isa<ConstantAggregateZero>(C))
634 C = Constant::getNullValue(ATy->getElementType());
635 else if (isa<UndefValue>(C))
636 C = UndefValue::get(ATy->getElementType());
639 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
640 if (CI->getZExtValue() >= PTy->getNumElements())
642 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
643 C = CP->getOperand(CI->getZExtValue());
644 else if (isa<ConstantAggregateZero>(C))
645 C = Constant::getNullValue(PTy->getElementType());
646 else if (isa<UndefValue>(C))
647 C = UndefValue::get(PTy->getElementType());
660 //===----------------------------------------------------------------------===//
661 // Constant Folding for Calls
664 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
665 /// the specified function.
667 llvm::canConstantFoldCallTo(const Function *F) {
668 switch (F->getIntrinsicID()) {
669 case Intrinsic::sqrt:
670 case Intrinsic::powi:
671 case Intrinsic::bswap:
672 case Intrinsic::ctpop:
673 case Intrinsic::ctlz:
674 case Intrinsic::cttz:
679 if (!F->hasName()) return false;
680 StringRef Name = F->getName();
682 // In these cases, the check of the length is required. We don't want to
683 // return true for a name like "cos\0blah" which strcmp would return equal to
684 // "cos", but has length 8.
686 default: return false;
688 return Name == "acos" || Name == "asin" ||
689 Name == "atan" || Name == "atan2";
691 return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
693 return Name == "exp";
695 return Name == "fabs" || Name == "fmod" || Name == "floor";
697 return Name == "log" || Name == "log10";
699 return Name == "pow";
701 return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
702 Name == "sinf" || Name == "sqrtf";
704 return Name == "tan" || Name == "tanh";
708 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
709 const Type *Ty, LLVMContext &Context) {
717 if (Ty == Type::getFloatTy(Context))
718 return ConstantFP::get(Context, APFloat((float)V));
719 if (Ty == Type::getDoubleTy(Context))
720 return ConstantFP::get(Context, APFloat(V));
721 llvm_unreachable("Can only constant fold float/double");
722 return 0; // dummy return to suppress warning
725 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
728 LLVMContext &Context) {
736 if (Ty == Type::getFloatTy(Context))
737 return ConstantFP::get(Context, APFloat((float)V));
738 if (Ty == Type::getDoubleTy(Context))
739 return ConstantFP::get(Context, APFloat(V));
740 llvm_unreachable("Can only constant fold float/double");
741 return 0; // dummy return to suppress warning
744 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
745 /// with the specified arguments, returning null if unsuccessful.
748 llvm::ConstantFoldCall(Function *F,
749 Constant* const* Operands, unsigned NumOperands) {
750 if (!F->hasName()) return 0;
751 LLVMContext &Context = F->getContext();
752 StringRef Name = F->getName();
754 const Type *Ty = F->getReturnType();
755 if (NumOperands == 1) {
756 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
757 if (Ty!=Type::getFloatTy(F->getContext()) &&
758 Ty!=Type::getDoubleTy(Context))
760 /// Currently APFloat versions of these functions do not exist, so we use
761 /// the host native double versions. Float versions are not called
762 /// directly but for all these it is true (float)(f((double)arg)) ==
763 /// f(arg). Long double not supported yet.
764 double V = Ty==Type::getFloatTy(F->getContext()) ?
765 (double)Op->getValueAPF().convertToFloat():
766 Op->getValueAPF().convertToDouble();
770 return ConstantFoldFP(acos, V, Ty, Context);
771 else if (Name == "asin")
772 return ConstantFoldFP(asin, V, Ty, Context);
773 else if (Name == "atan")
774 return ConstantFoldFP(atan, V, Ty, Context);
778 return ConstantFoldFP(ceil, V, Ty, Context);
779 else if (Name == "cos")
780 return ConstantFoldFP(cos, V, Ty, Context);
781 else if (Name == "cosh")
782 return ConstantFoldFP(cosh, V, Ty, Context);
783 else if (Name == "cosf")
784 return ConstantFoldFP(cos, V, Ty, Context);
788 return ConstantFoldFP(exp, V, Ty, Context);
792 return ConstantFoldFP(fabs, V, Ty, Context);
793 else if (Name == "floor")
794 return ConstantFoldFP(floor, V, Ty, Context);
797 if (Name == "log" && V > 0)
798 return ConstantFoldFP(log, V, Ty, Context);
799 else if (Name == "log10" && V > 0)
800 return ConstantFoldFP(log10, V, Ty, Context);
801 else if (Name == "llvm.sqrt.f32" ||
802 Name == "llvm.sqrt.f64") {
804 return ConstantFoldFP(sqrt, V, Ty, Context);
806 return Constant::getNullValue(Ty);
811 return ConstantFoldFP(sin, V, Ty, Context);
812 else if (Name == "sinh")
813 return ConstantFoldFP(sinh, V, Ty, Context);
814 else if (Name == "sqrt" && V >= 0)
815 return ConstantFoldFP(sqrt, V, Ty, Context);
816 else if (Name == "sqrtf" && V >= 0)
817 return ConstantFoldFP(sqrt, V, Ty, Context);
818 else if (Name == "sinf")
819 return ConstantFoldFP(sin, V, Ty, Context);
823 return ConstantFoldFP(tan, V, Ty, Context);
824 else if (Name == "tanh")
825 return ConstantFoldFP(tanh, V, Ty, Context);
830 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
831 if (Name.startswith("llvm.bswap"))
832 return ConstantInt::get(Context, Op->getValue().byteSwap());
833 else if (Name.startswith("llvm.ctpop"))
834 return ConstantInt::get(Ty, Op->getValue().countPopulation());
835 else if (Name.startswith("llvm.cttz"))
836 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
837 else if (Name.startswith("llvm.ctlz"))
838 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
840 } else if (NumOperands == 2) {
841 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
842 if (Ty!=Type::getFloatTy(F->getContext()) &&
843 Ty!=Type::getDoubleTy(Context))
845 double Op1V = Ty==Type::getFloatTy(F->getContext()) ?
846 (double)Op1->getValueAPF().convertToFloat():
847 Op1->getValueAPF().convertToDouble();
848 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
849 double Op2V = Ty==Type::getFloatTy(F->getContext()) ?
850 (double)Op2->getValueAPF().convertToFloat():
851 Op2->getValueAPF().convertToDouble();
854 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context);
855 } else if (Name == "fmod") {
856 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context);
857 } else if (Name == "atan2") {
858 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context);
860 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
861 if (Name == "llvm.powi.f32") {
862 return ConstantFP::get(Context, APFloat((float)std::pow((float)Op1V,
863 (int)Op2C->getZExtValue())));
864 } else if (Name == "llvm.powi.f64") {
865 return ConstantFP::get(Context, APFloat((double)std::pow((double)Op1V,
866 (int)Op2C->getZExtValue())));