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 Context->getConstantInt(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 if (!Ptr->isNullValue()) {
135 // If this is a inttoptr from a constant int, we can fold this as the base,
136 // otherwise we can't.
137 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
138 if (CE->getOpcode() == Instruction::IntToPtr)
139 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
140 BasePtr = Base->getZExtValue();
146 // If this is a constant expr gep that is effectively computing an
147 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
148 for (unsigned i = 1; i != NumOps; ++i)
149 if (!isa<ConstantInt>(Ops[i]))
152 uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
153 (Value**)Ops+1, NumOps-1);
154 Constant *C = Context->getConstantInt(TD->getIntPtrType(), Offset+BasePtr);
155 return Context->getConstantExprIntToPtr(C, ResultTy);
158 /// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
159 /// targetdata. Return 0 if unfoldable.
160 static Constant *FoldBitCast(Constant *C, const Type *DestTy,
161 const TargetData &TD, LLVMContext *Context) {
162 // If this is a bitcast from constant vector -> vector, fold it.
163 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
164 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
165 // If the element types match, VMCore can fold it.
166 unsigned NumDstElt = DestVTy->getNumElements();
167 unsigned NumSrcElt = CV->getNumOperands();
168 if (NumDstElt == NumSrcElt)
171 const Type *SrcEltTy = CV->getType()->getElementType();
172 const Type *DstEltTy = DestVTy->getElementType();
174 // Otherwise, we're changing the number of elements in a vector, which
175 // requires endianness information to do the right thing. For example,
176 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
177 // folds to (little endian):
178 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
179 // and to (big endian):
180 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
182 // First thing is first. We only want to think about integer here, so if
183 // we have something in FP form, recast it as integer.
184 if (DstEltTy->isFloatingPoint()) {
185 // Fold to an vector of integers with same size as our FP type.
186 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
187 const Type *DestIVTy = Context->getVectorType(
188 Context->getIntegerType(FPWidth), NumDstElt);
189 // Recursively handle this integer conversion, if possible.
190 C = FoldBitCast(C, DestIVTy, TD, Context);
193 // Finally, VMCore can handle this now that #elts line up.
194 return Context->getConstantExprBitCast(C, DestTy);
197 // Okay, we know the destination is integer, if the input is FP, convert
198 // it to integer first.
199 if (SrcEltTy->isFloatingPoint()) {
200 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
201 const Type *SrcIVTy = Context->getVectorType(
202 Context->getIntegerType(FPWidth), NumSrcElt);
203 // Ask VMCore to do the conversion now that #elts line up.
204 C = Context->getConstantExprBitCast(C, SrcIVTy);
205 CV = dyn_cast<ConstantVector>(C);
206 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
209 // Now we know that the input and output vectors are both integer vectors
210 // of the same size, and that their #elements is not the same. Do the
211 // conversion here, which depends on whether the input or output has
213 bool isLittleEndian = TD.isLittleEndian();
215 SmallVector<Constant*, 32> Result;
216 if (NumDstElt < NumSrcElt) {
217 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
218 Constant *Zero = Context->getNullValue(DstEltTy);
219 unsigned Ratio = NumSrcElt/NumDstElt;
220 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
222 for (unsigned i = 0; i != NumDstElt; ++i) {
223 // Build each element of the result.
224 Constant *Elt = Zero;
225 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
226 for (unsigned j = 0; j != Ratio; ++j) {
227 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
228 if (!Src) return 0; // Reject constantexpr elements.
230 // Zero extend the element to the right size.
231 Src = Context->getConstantExprZExt(Src, Elt->getType());
233 // Shift it to the right place, depending on endianness.
234 Src = Context->getConstantExprShl(Src,
235 Context->getConstantInt(Src->getType(), ShiftAmt));
236 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
239 Elt = Context->getConstantExprOr(Elt, Src);
241 Result.push_back(Elt);
244 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
245 unsigned Ratio = NumDstElt/NumSrcElt;
246 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
248 // Loop over each source value, expanding into multiple results.
249 for (unsigned i = 0; i != NumSrcElt; ++i) {
250 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
251 if (!Src) return 0; // Reject constantexpr elements.
253 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
254 for (unsigned j = 0; j != Ratio; ++j) {
255 // Shift the piece of the value into the right place, depending on
257 Constant *Elt = Context->getConstantExprLShr(Src,
258 Context->getConstantInt(Src->getType(), ShiftAmt));
259 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
261 // Truncate and remember this piece.
262 Result.push_back(Context->getConstantExprTrunc(Elt, DstEltTy));
267 return Context->getConstantVector(Result.data(), Result.size());
275 //===----------------------------------------------------------------------===//
276 // Constant Folding public APIs
277 //===----------------------------------------------------------------------===//
280 /// ConstantFoldInstruction - Attempt to constant fold the specified
281 /// instruction. If successful, the constant result is returned, if not, null
282 /// is returned. Note that this function can only fail when attempting to fold
283 /// instructions like loads and stores, which have no constant expression form.
285 Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext *Context,
286 const TargetData *TD) {
287 if (PHINode *PN = dyn_cast<PHINode>(I)) {
288 if (PN->getNumIncomingValues() == 0)
289 return Context->getUndef(PN->getType());
291 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
292 if (Result == 0) return 0;
294 // Handle PHI nodes specially here...
295 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
296 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
297 return 0; // Not all the same incoming constants...
299 // If we reach here, all incoming values are the same constant.
303 // Scan the operand list, checking to see if they are all constants, if so,
304 // hand off to ConstantFoldInstOperands.
305 SmallVector<Constant*, 8> Ops;
306 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
307 if (Constant *Op = dyn_cast<Constant>(*i))
310 return 0; // All operands not constant!
312 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
313 return ConstantFoldCompareInstOperands(CI->getPredicate(),
314 Ops.data(), Ops.size(),
317 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
318 Ops.data(), Ops.size(), Context, TD);
321 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
322 /// using the specified TargetData. If successful, the constant result is
323 /// result is returned, if not, null is returned.
324 Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
325 LLVMContext *Context,
326 const TargetData *TD) {
327 SmallVector<Constant*, 8> Ops;
328 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
329 Ops.push_back(cast<Constant>(*i));
332 return ConstantFoldCompareInstOperands(CE->getPredicate(),
333 Ops.data(), Ops.size(),
336 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
337 Ops.data(), Ops.size(), Context, TD);
340 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
341 /// specified opcode and operands. If successful, the constant result is
342 /// returned, if not, null is returned. Note that this function can fail when
343 /// attempting to fold instructions like loads and stores, which have no
344 /// constant expression form.
346 Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
347 Constant* const* Ops, unsigned NumOps,
348 LLVMContext *Context,
349 const TargetData *TD) {
350 // Handle easy binops first.
351 if (Instruction::isBinaryOp(Opcode)) {
352 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
353 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
357 return Context->getConstantExpr(Opcode, Ops[0], Ops[1]);
362 case Instruction::Call:
363 if (Function *F = dyn_cast<Function>(Ops[0]))
364 if (canConstantFoldCallTo(F))
365 return ConstantFoldCall(F, Ops+1, NumOps-1);
367 case Instruction::ICmp:
368 case Instruction::FCmp:
369 llvm_unreachable("This function is invalid for compares: no predicate specified");
370 case Instruction::PtrToInt:
371 // If the input is a inttoptr, eliminate the pair. This requires knowing
372 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
373 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
374 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
375 Constant *Input = CE->getOperand(0);
376 unsigned InWidth = Input->getType()->getScalarSizeInBits();
377 if (TD->getPointerSizeInBits() < InWidth) {
379 Context->getConstantInt(APInt::getLowBitsSet(InWidth,
380 TD->getPointerSizeInBits()));
381 Input = Context->getConstantExprAnd(Input, Mask);
383 // Do a zext or trunc to get to the dest size.
384 return Context->getConstantExprIntegerCast(Input, DestTy, false);
387 return Context->getConstantExprCast(Opcode, Ops[0], DestTy);
388 case Instruction::IntToPtr:
389 // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
390 // the int size is >= the ptr size. This requires knowing the width of a
391 // pointer, so it can't be done in ConstantExpr::getCast.
392 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
394 TD->getPointerSizeInBits() <=
395 CE->getType()->getScalarSizeInBits()) {
396 if (CE->getOpcode() == Instruction::PtrToInt) {
397 Constant *Input = CE->getOperand(0);
398 Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
399 return C ? C : Context->getConstantExprBitCast(Input, DestTy);
401 // If there's a constant offset added to the integer value before
402 // it is casted back to a pointer, see if the expression can be
403 // converted into a GEP.
404 if (CE->getOpcode() == Instruction::Add)
405 if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
406 if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
407 if (R->getOpcode() == Instruction::PtrToInt)
408 if (GlobalVariable *GV =
409 dyn_cast<GlobalVariable>(R->getOperand(0))) {
410 const PointerType *GVTy = cast<PointerType>(GV->getType());
411 if (const ArrayType *AT =
412 dyn_cast<ArrayType>(GVTy->getElementType())) {
413 const Type *ElTy = AT->getElementType();
414 uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
415 APInt PSA(L->getValue().getBitWidth(), AllocSize);
416 if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
417 L->getValue().urem(PSA) == 0) {
418 APInt ElemIdx = L->getValue().udiv(PSA);
419 if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
420 AT->getNumElements()))) {
421 Constant *Index[] = {
422 Context->getNullValue(CE->getType()),
423 Context->getConstantInt(ElemIdx)
426 Context->getConstantExprGetElementPtr(GV, &Index[0], 2);
433 return Context->getConstantExprCast(Opcode, Ops[0], DestTy);
434 case Instruction::Trunc:
435 case Instruction::ZExt:
436 case Instruction::SExt:
437 case Instruction::FPTrunc:
438 case Instruction::FPExt:
439 case Instruction::UIToFP:
440 case Instruction::SIToFP:
441 case Instruction::FPToUI:
442 case Instruction::FPToSI:
443 return Context->getConstantExprCast(Opcode, Ops[0], DestTy);
444 case Instruction::BitCast:
446 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
448 return Context->getConstantExprBitCast(Ops[0], DestTy);
449 case Instruction::Select:
450 return Context->getConstantExprSelect(Ops[0], Ops[1], Ops[2]);
451 case Instruction::ExtractElement:
452 return Context->getConstantExprExtractElement(Ops[0], Ops[1]);
453 case Instruction::InsertElement:
454 return Context->getConstantExprInsertElement(Ops[0], Ops[1], Ops[2]);
455 case Instruction::ShuffleVector:
456 return Context->getConstantExprShuffleVector(Ops[0], Ops[1], Ops[2]);
457 case Instruction::GetElementPtr:
458 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
461 return Context->getConstantExprGetElementPtr(Ops[0], Ops+1, NumOps-1);
465 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
466 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
467 /// returns a constant expression of the specified operands.
469 Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
470 Constant*const * Ops,
472 LLVMContext *Context,
473 const TargetData *TD) {
474 // fold: icmp (inttoptr x), null -> icmp x, 0
475 // fold: icmp (ptrtoint x), 0 -> icmp x, null
476 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
477 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
479 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
480 // around to know if bit truncation is happening.
481 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
482 if (TD && Ops[1]->isNullValue()) {
483 const Type *IntPtrTy = TD->getIntPtrType();
484 if (CE0->getOpcode() == Instruction::IntToPtr) {
485 // Convert the integer value to the right size to ensure we get the
486 // proper extension or truncation.
487 Constant *C = Context->getConstantExprIntegerCast(CE0->getOperand(0),
489 Constant *NewOps[] = { C, Context->getNullValue(C->getType()) };
490 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
494 // Only do this transformation if the int is intptrty in size, otherwise
495 // there is a truncation or extension that we aren't modeling.
496 if (CE0->getOpcode() == Instruction::PtrToInt &&
497 CE0->getType() == IntPtrTy) {
498 Constant *C = CE0->getOperand(0);
499 Constant *NewOps[] = { C, Context->getNullValue(C->getType()) };
501 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
506 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
507 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
508 const Type *IntPtrTy = TD->getIntPtrType();
510 if (CE0->getOpcode() == Instruction::IntToPtr) {
511 // Convert the integer value to the right size to ensure we get the
512 // proper extension or truncation.
513 Constant *C0 = Context->getConstantExprIntegerCast(CE0->getOperand(0),
515 Constant *C1 = Context->getConstantExprIntegerCast(CE1->getOperand(0),
517 Constant *NewOps[] = { C0, C1 };
518 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
522 // Only do this transformation if the int is intptrty in size, otherwise
523 // there is a truncation or extension that we aren't modeling.
524 if ((CE0->getOpcode() == Instruction::PtrToInt &&
525 CE0->getType() == IntPtrTy &&
526 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
527 Constant *NewOps[] = {
528 CE0->getOperand(0), CE1->getOperand(0)
530 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
536 return Context->getConstantExprCompare(Predicate, Ops[0], Ops[1]);
540 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
541 /// getelementptr constantexpr, return the constant value being addressed by the
542 /// constant expression, or null if something is funny and we can't decide.
543 Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
545 LLVMContext *Context) {
546 if (CE->getOperand(1) != Context->getNullValue(CE->getOperand(1)->getType()))
547 return 0; // Do not allow stepping over the value!
549 // Loop over all of the operands, tracking down which value we are
551 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
552 for (++I; I != E; ++I)
553 if (const StructType *STy = dyn_cast<StructType>(*I)) {
554 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
555 assert(CU->getZExtValue() < STy->getNumElements() &&
556 "Struct index out of range!");
557 unsigned El = (unsigned)CU->getZExtValue();
558 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
559 C = CS->getOperand(El);
560 } else if (isa<ConstantAggregateZero>(C)) {
561 C = Context->getNullValue(STy->getElementType(El));
562 } else if (isa<UndefValue>(C)) {
563 C = Context->getUndef(STy->getElementType(El));
567 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
568 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
569 if (CI->getZExtValue() >= ATy->getNumElements())
571 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
572 C = CA->getOperand(CI->getZExtValue());
573 else if (isa<ConstantAggregateZero>(C))
574 C = Context->getNullValue(ATy->getElementType());
575 else if (isa<UndefValue>(C))
576 C = Context->getUndef(ATy->getElementType());
579 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
580 if (CI->getZExtValue() >= PTy->getNumElements())
582 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
583 C = CP->getOperand(CI->getZExtValue());
584 else if (isa<ConstantAggregateZero>(C))
585 C = Context->getNullValue(PTy->getElementType());
586 else if (isa<UndefValue>(C))
587 C = Context->getUndef(PTy->getElementType());
600 //===----------------------------------------------------------------------===//
601 // Constant Folding for Calls
604 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
605 /// the specified function.
607 llvm::canConstantFoldCallTo(const Function *F) {
608 switch (F->getIntrinsicID()) {
609 case Intrinsic::sqrt:
610 case Intrinsic::powi:
611 case Intrinsic::bswap:
612 case Intrinsic::ctpop:
613 case Intrinsic::ctlz:
614 case Intrinsic::cttz:
619 if (!F->hasName()) return false;
620 const char *Str = F->getNameStart();
621 unsigned Len = F->getNameLen();
623 // In these cases, the check of the length is required. We don't want to
624 // return true for a name like "cos\0blah" which strcmp would return equal to
625 // "cos", but has length 8.
627 default: return false;
630 return !strcmp(Str, "acos") || !strcmp(Str, "asin") ||
631 !strcmp(Str, "atan");
633 return !strcmp(Str, "atan2");
637 return !strcmp(Str, "cos");
639 return !strcmp(Str, "ceil") || !strcmp(Str, "cosf") ||
640 !strcmp(Str, "cosh");
644 return !strcmp(Str, "exp");
648 return !strcmp(Str, "fabs") || !strcmp(Str, "fmod");
650 return !strcmp(Str, "floor");
654 if (Len == 3 && !strcmp(Str, "log"))
656 if (Len == 5 && !strcmp(Str, "log10"))
660 if (Len == 3 && !strcmp(Str, "pow"))
665 return !strcmp(Str, "sin");
667 return !strcmp(Str, "sinh") || !strcmp(Str, "sqrt") ||
668 !strcmp(Str, "sinf");
670 return !strcmp(Str, "sqrtf");
673 if (Len == 3 && !strcmp(Str, "tan"))
675 else if (Len == 4 && !strcmp(Str, "tanh"))
681 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
682 const Type *Ty, LLVMContext *Context) {
690 if (Ty == Type::FloatTy)
691 return Context->getConstantFP(APFloat((float)V));
692 if (Ty == Type::DoubleTy)
693 return Context->getConstantFP(APFloat(V));
694 llvm_unreachable("Can only constant fold float/double");
695 return 0; // dummy return to suppress warning
698 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
701 LLVMContext *Context) {
709 if (Ty == Type::FloatTy)
710 return Context->getConstantFP(APFloat((float)V));
711 if (Ty == Type::DoubleTy)
712 return Context->getConstantFP(APFloat(V));
713 llvm_unreachable("Can only constant fold float/double");
714 return 0; // dummy return to suppress warning
717 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
718 /// with the specified arguments, returning null if unsuccessful.
721 llvm::ConstantFoldCall(Function *F,
722 Constant* const* Operands, unsigned NumOperands) {
723 if (!F->hasName()) return 0;
724 LLVMContext *Context = F->getContext();
725 const char *Str = F->getNameStart();
726 unsigned Len = F->getNameLen();
728 const Type *Ty = F->getReturnType();
729 if (NumOperands == 1) {
730 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
731 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
733 /// Currently APFloat versions of these functions do not exist, so we use
734 /// the host native double versions. Float versions are not called
735 /// directly but for all these it is true (float)(f((double)arg)) ==
736 /// f(arg). Long double not supported yet.
737 double V = Ty==Type::FloatTy ? (double)Op->getValueAPF().convertToFloat():
738 Op->getValueAPF().convertToDouble();
741 if (Len == 4 && !strcmp(Str, "acos"))
742 return ConstantFoldFP(acos, V, Ty, Context);
743 else if (Len == 4 && !strcmp(Str, "asin"))
744 return ConstantFoldFP(asin, V, Ty, Context);
745 else if (Len == 4 && !strcmp(Str, "atan"))
746 return ConstantFoldFP(atan, V, Ty, Context);
749 if (Len == 4 && !strcmp(Str, "ceil"))
750 return ConstantFoldFP(ceil, V, Ty, Context);
751 else if (Len == 3 && !strcmp(Str, "cos"))
752 return ConstantFoldFP(cos, V, Ty, Context);
753 else if (Len == 4 && !strcmp(Str, "cosh"))
754 return ConstantFoldFP(cosh, V, Ty, Context);
755 else if (Len == 4 && !strcmp(Str, "cosf"))
756 return ConstantFoldFP(cos, V, Ty, Context);
759 if (Len == 3 && !strcmp(Str, "exp"))
760 return ConstantFoldFP(exp, V, Ty, Context);
763 if (Len == 4 && !strcmp(Str, "fabs"))
764 return ConstantFoldFP(fabs, V, Ty, Context);
765 else if (Len == 5 && !strcmp(Str, "floor"))
766 return ConstantFoldFP(floor, V, Ty, Context);
769 if (Len == 3 && !strcmp(Str, "log") && V > 0)
770 return ConstantFoldFP(log, V, Ty, Context);
771 else if (Len == 5 && !strcmp(Str, "log10") && V > 0)
772 return ConstantFoldFP(log10, V, Ty, Context);
773 else if (!strcmp(Str, "llvm.sqrt.f32") ||
774 !strcmp(Str, "llvm.sqrt.f64")) {
776 return ConstantFoldFP(sqrt, V, Ty, Context);
778 return Context->getNullValue(Ty);
782 if (Len == 3 && !strcmp(Str, "sin"))
783 return ConstantFoldFP(sin, V, Ty, Context);
784 else if (Len == 4 && !strcmp(Str, "sinh"))
785 return ConstantFoldFP(sinh, V, Ty, Context);
786 else if (Len == 4 && !strcmp(Str, "sqrt") && V >= 0)
787 return ConstantFoldFP(sqrt, V, Ty, Context);
788 else if (Len == 5 && !strcmp(Str, "sqrtf") && V >= 0)
789 return ConstantFoldFP(sqrt, V, Ty, Context);
790 else if (Len == 4 && !strcmp(Str, "sinf"))
791 return ConstantFoldFP(sin, V, Ty, Context);
794 if (Len == 3 && !strcmp(Str, "tan"))
795 return ConstantFoldFP(tan, V, Ty, Context);
796 else if (Len == 4 && !strcmp(Str, "tanh"))
797 return ConstantFoldFP(tanh, V, Ty, Context);
802 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
803 if (Len > 11 && !memcmp(Str, "llvm.bswap", 10))
804 return Context->getConstantInt(Op->getValue().byteSwap());
805 else if (Len > 11 && !memcmp(Str, "llvm.ctpop", 10))
806 return Context->getConstantInt(Ty, Op->getValue().countPopulation());
807 else if (Len > 10 && !memcmp(Str, "llvm.cttz", 9))
808 return Context->getConstantInt(Ty, Op->getValue().countTrailingZeros());
809 else if (Len > 10 && !memcmp(Str, "llvm.ctlz", 9))
810 return Context->getConstantInt(Ty, Op->getValue().countLeadingZeros());
812 } else if (NumOperands == 2) {
813 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
814 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
816 double Op1V = Ty==Type::FloatTy ?
817 (double)Op1->getValueAPF().convertToFloat():
818 Op1->getValueAPF().convertToDouble();
819 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
820 double Op2V = Ty==Type::FloatTy ?
821 (double)Op2->getValueAPF().convertToFloat():
822 Op2->getValueAPF().convertToDouble();
824 if (Len == 3 && !strcmp(Str, "pow")) {
825 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty, Context);
826 } else if (Len == 4 && !strcmp(Str, "fmod")) {
827 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty, Context);
828 } else if (Len == 5 && !strcmp(Str, "atan2")) {
829 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty, Context);
831 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
832 if (!strcmp(Str, "llvm.powi.f32")) {
833 return Context->getConstantFP(APFloat((float)std::pow((float)Op1V,
834 (int)Op2C->getZExtValue())));
835 } else if (!strcmp(Str, "llvm.powi.f64")) {
836 return Context->getConstantFP(APFloat((double)std::pow((double)Op1V,
837 (int)Op2C->getZExtValue())));