+/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
+/// Attempt to symbolically evaluate the result of a binary operator merging
+/// these together. If target data info is available, it is provided as TD,
+/// otherwise TD is null.
+static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
+ Constant *Op1, const TargetData *TD,
+ LLVMContext &Context){
+ // SROA
+
+ // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
+ // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
+ // bits.
+
+
+ // If the constant expr is something like &A[123] - &A[4].f, fold this into a
+ // constant. This happens frequently when iterating over a global array.
+ if (Opc == Instruction::Sub && TD) {
+ GlobalValue *GV1, *GV2;
+ int64_t Offs1, Offs2;
+
+ if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
+ if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
+ GV1 == GV2) {
+ // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
+ return ConstantInt::get(Op0->getType(), Offs1-Offs2);
+ }
+ }
+
+ return 0;
+}
+
+/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
+/// constant expression, do so.
+static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
+ const Type *ResultTy,
+ LLVMContext &Context,
+ const TargetData *TD) {
+ Constant *Ptr = Ops[0];
+ if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
+ return 0;
+
+ uint64_t BasePtr = 0;
+ if (!Ptr->isNullValue()) {
+ // If this is a inttoptr from a constant int, we can fold this as the base,
+ // otherwise we can't.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
+ if (CE->getOpcode() == Instruction::IntToPtr)
+ if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
+ BasePtr = Base->getZExtValue();
+
+ if (BasePtr == 0)
+ return 0;
+ }
+
+ // If this is a constant expr gep that is effectively computing an
+ // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
+ for (unsigned i = 1; i != NumOps; ++i)
+ if (!isa<ConstantInt>(Ops[i]))
+ return false;
+
+ uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
+ (Value**)Ops+1, NumOps-1);
+ Constant *C = ConstantInt::get(TD->getIntPtrType(Context), Offset+BasePtr);
+ return ConstantExpr::getIntToPtr(C, ResultTy);
+}
+
+/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
+/// targetdata. Return 0 if unfoldable.
+static Constant *FoldBitCast(Constant *C, const Type *DestTy,
+ const TargetData &TD, LLVMContext &Context) {
+ // If this is a bitcast from constant vector -> vector, fold it.
+ if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
+ if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
+ // If the element types match, VMCore can fold it.
+ unsigned NumDstElt = DestVTy->getNumElements();
+ unsigned NumSrcElt = CV->getNumOperands();
+ if (NumDstElt == NumSrcElt)
+ return 0;
+
+ const Type *SrcEltTy = CV->getType()->getElementType();
+ const Type *DstEltTy = DestVTy->getElementType();
+
+ // Otherwise, we're changing the number of elements in a vector, which
+ // requires endianness information to do the right thing. For example,
+ // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
+ // folds to (little endian):
+ // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
+ // and to (big endian):
+ // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
+
+ // First thing is first. We only want to think about integer here, so if
+ // we have something in FP form, recast it as integer.
+ if (DstEltTy->isFloatingPoint()) {
+ // Fold to an vector of integers with same size as our FP type.
+ unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
+ const Type *DestIVTy = VectorType::get(
+ IntegerType::get(Context, FPWidth), NumDstElt);
+ // Recursively handle this integer conversion, if possible.
+ C = FoldBitCast(C, DestIVTy, TD, Context);
+ if (!C) return 0;
+
+ // Finally, VMCore can handle this now that #elts line up.
+ return ConstantExpr::getBitCast(C, DestTy);
+ }
+
+ // Okay, we know the destination is integer, if the input is FP, convert
+ // it to integer first.
+ if (SrcEltTy->isFloatingPoint()) {
+ unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
+ const Type *SrcIVTy = VectorType::get(
+ IntegerType::get(Context, FPWidth), NumSrcElt);
+ // Ask VMCore to do the conversion now that #elts line up.
+ C = ConstantExpr::getBitCast(C, SrcIVTy);
+ CV = dyn_cast<ConstantVector>(C);
+ if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
+ }
+
+ // Now we know that the input and output vectors are both integer vectors
+ // of the same size, and that their #elements is not the same. Do the
+ // conversion here, which depends on whether the input or output has
+ // more elements.
+ bool isLittleEndian = TD.isLittleEndian();
+
+ SmallVector<Constant*, 32> Result;
+ if (NumDstElt < NumSrcElt) {
+ // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
+ Constant *Zero = Constant::getNullValue(DstEltTy);
+ unsigned Ratio = NumSrcElt/NumDstElt;
+ unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
+ unsigned SrcElt = 0;
+ for (unsigned i = 0; i != NumDstElt; ++i) {
+ // Build each element of the result.
+ Constant *Elt = Zero;
+ unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
+ for (unsigned j = 0; j != Ratio; ++j) {
+ Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
+ if (!Src) return 0; // Reject constantexpr elements.
+
+ // Zero extend the element to the right size.
+ Src = ConstantExpr::getZExt(Src, Elt->getType());
+
+ // Shift it to the right place, depending on endianness.
+ Src = ConstantExpr::getShl(Src,
+ ConstantInt::get(Src->getType(), ShiftAmt));
+ ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
+
+ // Mix it in.
+ Elt = ConstantExpr::getOr(Elt, Src);
+ }
+ Result.push_back(Elt);
+ }
+ } else {
+ // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
+ unsigned Ratio = NumDstElt/NumSrcElt;
+ unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
+
+ // Loop over each source value, expanding into multiple results.
+ for (unsigned i = 0; i != NumSrcElt; ++i) {
+ Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
+ if (!Src) return 0; // Reject constantexpr elements.
+
+ unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
+ for (unsigned j = 0; j != Ratio; ++j) {
+ // Shift the piece of the value into the right place, depending on
+ // endianness.
+ Constant *Elt = ConstantExpr::getLShr(Src,
+ ConstantInt::get(Src->getType(), ShiftAmt));
+ ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
+
+ // Truncate and remember this piece.
+ Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
+ }
+ }
+ }
+
+ return ConstantVector::get(Result.data(), Result.size());
+ }
+ }
+
+ return 0;
+}
+
+
+//===----------------------------------------------------------------------===//
+// Constant Folding public APIs
+//===----------------------------------------------------------------------===//
+
+
+/// ConstantFoldInstruction - Attempt to constant fold the specified
+/// instruction. If successful, the constant result is returned, if not, null
+/// is returned. Note that this function can only fail when attempting to fold
+/// instructions like loads and stores, which have no constant expression form.
+///
+Constant *llvm::ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
+ const TargetData *TD) {
+ if (PHINode *PN = dyn_cast<PHINode>(I)) {
+ if (PN->getNumIncomingValues() == 0)
+ return UndefValue::get(PN->getType());
+
+ Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
+ if (Result == 0) return 0;
+
+ // Handle PHI nodes specially here...
+ for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
+ return 0; // Not all the same incoming constants...
+
+ // If we reach here, all incoming values are the same constant.
+ return Result;
+ }
+
+ // Scan the operand list, checking to see if they are all constants, if so,
+ // hand off to ConstantFoldInstOperands.
+ SmallVector<Constant*, 8> Ops;
+ for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
+ if (Constant *Op = dyn_cast<Constant>(*i))
+ Ops.push_back(Op);
+ else
+ return 0; // All operands not constant!
+
+ if (const CmpInst *CI = dyn_cast<CmpInst>(I))
+ return ConstantFoldCompareInstOperands(CI->getPredicate(),
+ Ops.data(), Ops.size(),
+ Context, TD);
+ else
+ return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
+ Ops.data(), Ops.size(), Context, TD);
+}
+
+/// ConstantFoldConstantExpression - Attempt to fold the constant expression
+/// using the specified TargetData. If successful, the constant result is
+/// result is returned, if not, null is returned.
+Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
+ LLVMContext &Context,
+ const TargetData *TD) {
+ SmallVector<Constant*, 8> Ops;
+ for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
+ Ops.push_back(cast<Constant>(*i));
+
+ if (CE->isCompare())
+ return ConstantFoldCompareInstOperands(CE->getPredicate(),
+ Ops.data(), Ops.size(),
+ Context, TD);
+ else
+ return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
+ Ops.data(), Ops.size(), Context, TD);
+}
+
+/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
+/// specified opcode and operands. If successful, the constant result is
+/// returned, if not, null is returned. Note that this function can fail when
+/// attempting to fold instructions like loads and stores, which have no
+/// constant expression form.
+///
+Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
+ Constant* const* Ops, unsigned NumOps,
+ LLVMContext &Context,
+ const TargetData *TD) {
+ // Handle easy binops first.
+ if (Instruction::isBinaryOp(Opcode)) {
+ if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
+ if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD,
+ Context))
+ return C;
+
+ return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
+ }
+
+ switch (Opcode) {
+ default: return 0;
+ case Instruction::Call:
+ if (Function *F = dyn_cast<Function>(Ops[0]))
+ if (canConstantFoldCallTo(F))
+ return ConstantFoldCall(F, Ops+1, NumOps-1);
+ return 0;
+ case Instruction::ICmp:
+ case Instruction::FCmp:
+ llvm_unreachable("This function is invalid for compares: no predicate specified");
+ case Instruction::PtrToInt:
+ // If the input is a inttoptr, eliminate the pair. This requires knowing
+ // the width of a pointer, so it can't be done in ConstantExpr::getCast.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
+ if (TD && CE->getOpcode() == Instruction::IntToPtr) {
+ Constant *Input = CE->getOperand(0);
+ unsigned InWidth = Input->getType()->getScalarSizeInBits();
+ if (TD->getPointerSizeInBits() < InWidth) {
+ Constant *Mask =
+ ConstantInt::get(Context, APInt::getLowBitsSet(InWidth,
+ TD->getPointerSizeInBits()));
+ Input = ConstantExpr::getAnd(Input, Mask);
+ }
+ // Do a zext or trunc to get to the dest size.
+ return ConstantExpr::getIntegerCast(Input, DestTy, false);
+ }
+ }
+ return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
+ case Instruction::IntToPtr:
+ // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
+ // the int size is >= the ptr size. This requires knowing the width of a
+ // pointer, so it can't be done in ConstantExpr::getCast.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
+ if (TD &&
+ TD->getPointerSizeInBits() <=
+ CE->getType()->getScalarSizeInBits()) {
+ if (CE->getOpcode() == Instruction::PtrToInt) {
+ Constant *Input = CE->getOperand(0);
+ Constant *C = FoldBitCast(Input, DestTy, *TD, Context);
+ return C ? C : ConstantExpr::getBitCast(Input, DestTy);
+ }
+ // If there's a constant offset added to the integer value before
+ // it is casted back to a pointer, see if the expression can be
+ // converted into a GEP.
+ if (CE->getOpcode() == Instruction::Add)
+ if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
+ if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
+ if (R->getOpcode() == Instruction::PtrToInt)
+ if (GlobalVariable *GV =
+ dyn_cast<GlobalVariable>(R->getOperand(0))) {
+ const PointerType *GVTy = cast<PointerType>(GV->getType());
+ if (const ArrayType *AT =
+ dyn_cast<ArrayType>(GVTy->getElementType())) {
+ const Type *ElTy = AT->getElementType();
+ uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
+ APInt PSA(L->getValue().getBitWidth(), AllocSize);
+ if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
+ L->getValue().urem(PSA) == 0) {
+ APInt ElemIdx = L->getValue().udiv(PSA);
+ if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
+ AT->getNumElements()))) {
+ Constant *Index[] = {
+ Constant::getNullValue(CE->getType()),
+ ConstantInt::get(Context, ElemIdx)
+ };
+ return
+ ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
+ }
+ }
+ }
+ }
+ }
+ }
+ return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
+ case Instruction::Trunc:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ case Instruction::FPTrunc:
+ case Instruction::FPExt:
+ case Instruction::UIToFP:
+ case Instruction::SIToFP:
+ case Instruction::FPToUI:
+ case Instruction::FPToSI:
+ return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
+ case Instruction::BitCast:
+ if (TD)
+ if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
+ return C;
+ return ConstantExpr::getBitCast(Ops[0], DestTy);
+ case Instruction::Select:
+ return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
+ case Instruction::ExtractElement:
+ return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
+ case Instruction::InsertElement:
+ return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
+ case Instruction::ShuffleVector:
+ return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
+ case Instruction::GetElementPtr:
+ if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, Context, TD))
+ return C;
+
+ return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
+ }
+}
+
+/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
+/// instruction (icmp/fcmp) with the specified operands. If it fails, it
+/// returns a constant expression of the specified operands.
+///
+Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
+ Constant*const * Ops,
+ unsigned NumOps,
+ LLVMContext &Context,
+ const TargetData *TD) {
+ // fold: icmp (inttoptr x), null -> icmp x, 0
+ // fold: icmp (ptrtoint x), 0 -> icmp x, null
+ // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
+ // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
+ //
+ // ConstantExpr::getCompare cannot do this, because it doesn't have TD
+ // around to know if bit truncation is happening.
+ if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
+ if (TD && Ops[1]->isNullValue()) {
+ const Type *IntPtrTy = TD->getIntPtrType(Context);
+ if (CE0->getOpcode() == Instruction::IntToPtr) {
+ // Convert the integer value to the right size to ensure we get the
+ // proper extension or truncation.
+ Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
+ IntPtrTy, false);
+ Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
+ return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
+ Context, TD);
+ }
+
+ // Only do this transformation if the int is intptrty in size, otherwise
+ // there is a truncation or extension that we aren't modeling.
+ if (CE0->getOpcode() == Instruction::PtrToInt &&
+ CE0->getType() == IntPtrTy) {
+ Constant *C = CE0->getOperand(0);
+ Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
+ // FIXME!
+ return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
+ Context, TD);
+ }
+ }
+
+ if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
+ if (TD && CE0->getOpcode() == CE1->getOpcode()) {
+ const Type *IntPtrTy = TD->getIntPtrType(Context);
+
+ if (CE0->getOpcode() == Instruction::IntToPtr) {
+ // Convert the integer value to the right size to ensure we get the
+ // proper extension or truncation.
+ Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
+ IntPtrTy, false);
+ Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
+ IntPtrTy, false);
+ Constant *NewOps[] = { C0, C1 };
+ return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
+ Context, TD);
+ }
+
+ // Only do this transformation if the int is intptrty in size, otherwise
+ // there is a truncation or extension that we aren't modeling.
+ if ((CE0->getOpcode() == Instruction::PtrToInt &&
+ CE0->getType() == IntPtrTy &&
+ CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
+ Constant *NewOps[] = {
+ CE0->getOperand(0), CE1->getOperand(0)
+ };
+ return ConstantFoldCompareInstOperands(Predicate, NewOps, 2,
+ Context, TD);
+ }
+ }
+ }
+ }
+ return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
+}
+
+
+/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
+/// getelementptr constantexpr, return the constant value being addressed by the
+/// constant expression, or null if something is funny and we can't decide.
+Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
+ ConstantExpr *CE,
+ LLVMContext &Context) {
+ if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
+ return 0; // Do not allow stepping over the value!
+
+ // Loop over all of the operands, tracking down which value we are
+ // addressing...
+ gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
+ for (++I; I != E; ++I)
+ if (const StructType *STy = dyn_cast<StructType>(*I)) {
+ ConstantInt *CU = cast<ConstantInt>(I.getOperand());
+ assert(CU->getZExtValue() < STy->getNumElements() &&
+ "Struct index out of range!");
+ unsigned El = (unsigned)CU->getZExtValue();
+ if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
+ C = CS->getOperand(El);
+ } else if (isa<ConstantAggregateZero>(C)) {
+ C = Constant::getNullValue(STy->getElementType(El));
+ } else if (isa<UndefValue>(C)) {
+ C = UndefValue::get(STy->getElementType(El));
+ } else {
+ return 0;
+ }
+ } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
+ if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
+ if (CI->getZExtValue() >= ATy->getNumElements())
+ return 0;
+ if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
+ C = CA->getOperand(CI->getZExtValue());
+ else if (isa<ConstantAggregateZero>(C))
+ C = Constant::getNullValue(ATy->getElementType());
+ else if (isa<UndefValue>(C))
+ C = UndefValue::get(ATy->getElementType());
+ else
+ return 0;
+ } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
+ if (CI->getZExtValue() >= PTy->getNumElements())
+ return 0;
+ if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
+ C = CP->getOperand(CI->getZExtValue());
+ else if (isa<ConstantAggregateZero>(C))
+ C = Constant::getNullValue(PTy->getElementType());
+ else if (isa<UndefValue>(C))
+ C = UndefValue::get(PTy->getElementType());
+ else
+ return 0;
+ } else {
+ return 0;
+ }
+ } else {
+ return 0;
+ }
+ return C;
+}
+
+
+//===----------------------------------------------------------------------===//
+// Constant Folding for Calls
+//
+