+
+
+Constant *llvm::ConstantFoldCastInstruction(const Constant *V,
+ const Type *DestTy) {
+ if (V->getType() == DestTy) return (Constant*)V;
+
+ // Cast of a global address to boolean is always true.
+ if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
+ if (DestTy == Type::BoolTy)
+ // FIXME: When we support 'external weak' references, we have to prevent
+ // this transformation from happening. This code will need to be updated
+ // to ignore external weak symbols when we support it.
+ return ConstantBool::getTrue();
+ } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+ if (CE->getOpcode() == Instruction::Cast) {
+ Constant *Op = const_cast<Constant*>(CE->getOperand(0));
+ // Try to not produce a cast of a cast, which is almost always redundant.
+ if (!Op->getType()->isFloatingPoint() &&
+ !CE->getType()->isFloatingPoint() &&
+ !DestTy->isFloatingPoint()) {
+ unsigned S1 = getSize(Op->getType()), S2 = getSize(CE->getType());
+ unsigned S3 = getSize(DestTy);
+ if (Op->getType() == DestTy && S3 >= S2)
+ return Op;
+ if (S1 >= S2 && S2 >= S3)
+ return ConstantExpr::getCast(Op, DestTy);
+ if (S1 <= S2 && S2 >= S3 && S1 <= S3)
+ return ConstantExpr::getCast(Op, DestTy);
+ }
+ } else if (CE->getOpcode() == Instruction::GetElementPtr) {
+ // If all of the indexes in the GEP are null values, there is no pointer
+ // adjustment going on. We might as well cast the source pointer.
+ bool isAllNull = true;
+ for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
+ if (!CE->getOperand(i)->isNullValue()) {
+ isAllNull = false;
+ break;
+ }
+ if (isAllNull)
+ return ConstantExpr::getCast(CE->getOperand(0), DestTy);
+ }
+ } else if (isa<UndefValue>(V)) {
+ return UndefValue::get(DestTy);
+ }
+
+ // Check to see if we are casting an pointer to an aggregate to a pointer to
+ // the first element. If so, return the appropriate GEP instruction.
+ if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
+ if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) {
+ std::vector<Value*> IdxList;
+ IdxList.push_back(Constant::getNullValue(Type::IntTy));
+ const Type *ElTy = PTy->getElementType();
+ while (ElTy != DPTy->getElementType()) {
+ if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
+ if (STy->getNumElements() == 0) break;
+ ElTy = STy->getElementType(0);
+ IdxList.push_back(Constant::getNullValue(Type::UIntTy));
+ } else if (const SequentialType *STy = dyn_cast<SequentialType>(ElTy)) {
+ if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
+ ElTy = STy->getElementType();
+ IdxList.push_back(IdxList[0]);
+ } else {
+ break;
+ }
+ }
+
+ if (ElTy == DPTy->getElementType())
+ return ConstantExpr::getGetElementPtr(const_cast<Constant*>(V),IdxList);
+ }
+
+ // Handle casts from one packed constant to another. We know that the src and
+ // dest type have the same size.
+ if (const PackedType *DestPTy = dyn_cast<PackedType>(DestTy)) {
+ if (const PackedType *SrcTy = dyn_cast<PackedType>(V->getType())) {
+ assert(DestPTy->getElementType()->getPrimitiveSizeInBits() *
+ DestPTy->getNumElements() ==
+ SrcTy->getElementType()->getPrimitiveSizeInBits() *
+ SrcTy->getNumElements() && "Not cast between same sized vectors!");
+ if (isa<ConstantAggregateZero>(V))
+ return Constant::getNullValue(DestTy);
+ if (isa<UndefValue>(V))
+ return UndefValue::get(DestTy);
+ if (const ConstantPacked *CP = dyn_cast<ConstantPacked>(V)) {
+ // This is a cast from a ConstantPacked of one type to a ConstantPacked
+ // of another type. Check to see if all elements of the input are
+ // simple.
+ bool AllSimpleConstants = true;
+ for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) {
+ if (!isa<ConstantInt>(CP->getOperand(i)) &&
+ !isa<ConstantFP>(CP->getOperand(i))) {
+ AllSimpleConstants = false;
+ break;
+ }
+ }
+
+ // If all of the elements are simple constants, we can fold this.
+ if (AllSimpleConstants)
+ return CastConstantPacked(const_cast<ConstantPacked*>(CP), DestPTy);
+ }
+ }
+ }
+
+ ConstRules &Rules = ConstRules::get(V, V);
+
+ switch (DestTy->getTypeID()) {
+ case Type::BoolTyID: return Rules.castToBool(V);
+ case Type::UByteTyID: return Rules.castToUByte(V);
+ case Type::SByteTyID: return Rules.castToSByte(V);
+ case Type::UShortTyID: return Rules.castToUShort(V);
+ case Type::ShortTyID: return Rules.castToShort(V);
+ case Type::UIntTyID: return Rules.castToUInt(V);
+ case Type::IntTyID: return Rules.castToInt(V);
+ case Type::ULongTyID: return Rules.castToULong(V);
+ case Type::LongTyID: return Rules.castToLong(V);
+ case Type::FloatTyID: return Rules.castToFloat(V);
+ case Type::DoubleTyID: return Rules.castToDouble(V);
+ case Type::PointerTyID:
+ return Rules.castToPointer(V, cast<PointerType>(DestTy));
+ default: return 0;
+ }
+}
+
+Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond,
+ const Constant *V1,
+ const Constant *V2) {
+ if (const ConstantBool *CB = dyn_cast<ConstantBool>(Cond))
+ return const_cast<Constant*>(CB->getValue() ? V1 : V2);
+
+ if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
+ if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
+ if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
+ if (V1 == V2) return const_cast<Constant*>(V1);
+ return 0;
+}
+
+Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val,
+ const Constant *Idx) {
+ if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
+ return UndefValue::get(cast<PackedType>(Val->getType())->getElementType());
+ if (Val->isNullValue()) // ee(zero, x) -> zero
+ return Constant::getNullValue(
+ cast<PackedType>(Val->getType())->getElementType());
+
+ if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) {
+ if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
+ return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
+ } else if (isa<UndefValue>(Idx)) {
+ // ee({w,x,y,z}, undef) -> w (an arbitrary value).
+ return const_cast<Constant*>(CVal->getOperand(0));
+ }
+ }
+ return 0;
+}
+
+Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val,
+ const Constant *Elt,
+ const Constant *Idx) {
+ const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
+ if (!CIdx) return 0;
+ uint64_t idxVal = CIdx->getZExtValue();
+ if (const UndefValue *UVal = dyn_cast<UndefValue>(Val)) {
+ // Insertion of scalar constant into packed undef
+ // Optimize away insertion of undef
+ if (isa<UndefValue>(Elt))
+ return const_cast<Constant*>(Val);
+ // Otherwise break the aggregate undef into multiple undefs and do
+ // the insertion
+ unsigned numOps =
+ cast<PackedType>(Val->getType())->getNumElements();
+ std::vector<Constant*> Ops;
+ Ops.reserve(numOps);
+ for (unsigned i = 0; i < numOps; ++i) {
+ const Constant *Op =
+ (i == idxVal) ? Elt : UndefValue::get(Elt->getType());
+ Ops.push_back(const_cast<Constant*>(Op));
+ }
+ return ConstantPacked::get(Ops);
+ }
+ if (const ConstantAggregateZero *CVal =
+ dyn_cast<ConstantAggregateZero>(Val)) {
+ // Insertion of scalar constant into packed aggregate zero
+ // Optimize away insertion of zero
+ if (Elt->isNullValue())
+ return const_cast<Constant*>(Val);
+ // Otherwise break the aggregate zero into multiple zeros and do
+ // the insertion
+ unsigned numOps =
+ cast<PackedType>(Val->getType())->getNumElements();
+ std::vector<Constant*> Ops;
+ Ops.reserve(numOps);
+ for (unsigned i = 0; i < numOps; ++i) {
+ const Constant *Op =
+ (i == idxVal) ? Elt : Constant::getNullValue(Elt->getType());
+ Ops.push_back(const_cast<Constant*>(Op));
+ }
+ return ConstantPacked::get(Ops);
+ }
+ if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) {
+ // Insertion of scalar constant into packed constant
+ std::vector<Constant*> Ops;
+ Ops.reserve(CVal->getNumOperands());
+ for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
+ const Constant *Op =
+ (i == idxVal) ? Elt : cast<Constant>(CVal->getOperand(i));
+ Ops.push_back(const_cast<Constant*>(Op));
+ }
+ return ConstantPacked::get(Ops);
+ }
+ return 0;
+}
+
+Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
+ const Constant *V2,
+ const Constant *Mask) {
+ // TODO:
+ return 0;
+}
+
+
+/// isZeroSizedType - This type is zero sized if its an array or structure of
+/// zero sized types. The only leaf zero sized type is an empty structure.
+static bool isMaybeZeroSizedType(const Type *Ty) {
+ if (isa<OpaqueType>(Ty)) return true; // Can't say.
+ if (const StructType *STy = dyn_cast<StructType>(Ty)) {
+
+ // If all of elements have zero size, this does too.
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
+ return true;
+
+ } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
+ return isMaybeZeroSizedType(ATy->getElementType());
+ }
+ return false;
+}
+
+/// IdxCompare - Compare the two constants as though they were getelementptr
+/// indices. This allows coersion of the types to be the same thing.
+///
+/// If the two constants are the "same" (after coersion), return 0. If the
+/// first is less than the second, return -1, if the second is less than the
+/// first, return 1. If the constants are not integral, return -2.
+///
+static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) {
+ if (C1 == C2) return 0;
+
+ // Ok, we found a different index. Are either of the operands
+ // ConstantExprs? If so, we can't do anything with them.
+ if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
+ return -2; // don't know!
+
+ // Ok, we have two differing integer indices. Sign extend them to be the same
+ // type. Long is always big enough, so we use it.
+ C1 = ConstantExpr::getSignExtend(C1, Type::LongTy);
+ C2 = ConstantExpr::getSignExtend(C2, Type::LongTy);
+ if (C1 == C2) return 0; // Are they just differing types?
+
+ // If the type being indexed over is really just a zero sized type, there is
+ // no pointer difference being made here.
+ if (isMaybeZeroSizedType(ElTy))
+ return -2; // dunno.
+
+ // If they are really different, now that they are the same type, then we
+ // found a difference!
+ if (cast<ConstantInt>(C1)->getSExtValue() <
+ cast<ConstantInt>(C2)->getSExtValue())
+ return -1;
+ else
+ return 1;
+}
+
+/// evaluateRelation - This function determines if there is anything we can
+/// decide about the two constants provided. This doesn't need to handle simple
+/// things like integer comparisons, but should instead handle ConstantExprs
+/// and GlobalValuess. If we can determine that the two constants have a
+/// particular relation to each other, we should return the corresponding SetCC
+/// code, otherwise return Instruction::BinaryOpsEnd.
+///
+/// To simplify this code we canonicalize the relation so that the first
+/// operand is always the most "complex" of the two. We consider simple
+/// constants (like ConstantInt) to be the simplest, followed by
+/// GlobalValues, followed by ConstantExpr's (the most complex).
+///
+static Instruction::BinaryOps evaluateRelation(Constant *V1, Constant *V2) {
+ assert(V1->getType() == V2->getType() &&
+ "Cannot compare different types of values!");
+ if (V1 == V2) return Instruction::SetEQ;
+
+ if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
+ if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
+ // We distilled this down to a simple case, use the standard constant
+ // folder.
+ ConstantBool *R = dyn_cast<ConstantBool>(ConstantExpr::getSetEQ(V1, V2));
+ if (R && R->getValue()) return Instruction::SetEQ;
+ R = dyn_cast<ConstantBool>(ConstantExpr::getSetLT(V1, V2));
+ if (R && R->getValue()) return Instruction::SetLT;
+ R = dyn_cast<ConstantBool>(ConstantExpr::getSetGT(V1, V2));
+ if (R && R->getValue()) return Instruction::SetGT;
+
+ // If we couldn't figure it out, bail.
+ return Instruction::BinaryOpsEnd;
+ }
+
+ // If the first operand is simple, swap operands.
+ Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
+ if (SwappedRelation != Instruction::BinaryOpsEnd)
+ return SetCondInst::getSwappedCondition(SwappedRelation);
+
+ } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
+ if (isa<ConstantExpr>(V2)) { // Swap as necessary.
+ Instruction::BinaryOps SwappedRelation = evaluateRelation(V2, V1);
+ if (SwappedRelation != Instruction::BinaryOpsEnd)
+ return SetCondInst::getSwappedCondition(SwappedRelation);
+ else
+ return Instruction::BinaryOpsEnd;
+ }
+
+ // Now we know that the RHS is a GlobalValue or simple constant,
+ // which (since the types must match) means that it's a ConstantPointerNull.
+ if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
+ assert(CPR1 != CPR2 &&
+ "GVs for the same value exist at different addresses??");
+ // FIXME: If both globals are external weak, they might both be null!
+ return Instruction::SetNE;
+ } else {
+ assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
+ // Global can never be null. FIXME: if we implement external weak
+ // linkage, this is not necessarily true!
+ return Instruction::SetNE;
+ }
+
+ } else {
+ // Ok, the LHS is known to be a constantexpr. The RHS can be any of a
+ // constantexpr, a CPR, or a simple constant.
+ ConstantExpr *CE1 = cast<ConstantExpr>(V1);
+ Constant *CE1Op0 = CE1->getOperand(0);
+
+ switch (CE1->getOpcode()) {
+ case Instruction::Cast:
+ // If the cast is not actually changing bits, and the second operand is a
+ // null pointer, do the comparison with the pre-casted value.
+ if (V2->isNullValue() &&
+ (isa<PointerType>(CE1->getType()) || CE1->getType()->isIntegral()))
+ return evaluateRelation(CE1Op0,
+ Constant::getNullValue(CE1Op0->getType()));
+
+ // If the dest type is a pointer type, and the RHS is a constantexpr cast
+ // from the same type as the src of the LHS, evaluate the inputs. This is
+ // important for things like "seteq (cast 4 to int*), (cast 5 to int*)",
+ // which happens a lot in compilers with tagged integers.
+ if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
+ if (isa<PointerType>(CE1->getType()) &&
+ CE2->getOpcode() == Instruction::Cast &&
+ CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
+ CE1->getOperand(0)->getType()->isIntegral()) {
+ return evaluateRelation(CE1->getOperand(0), CE2->getOperand(0));
+ }
+ break;
+
+ case Instruction::GetElementPtr:
+ // Ok, since this is a getelementptr, we know that the constant has a
+ // pointer type. Check the various cases.
+ if (isa<ConstantPointerNull>(V2)) {
+ // If we are comparing a GEP to a null pointer, check to see if the base
+ // of the GEP equals the null pointer.
+ if (isa<GlobalValue>(CE1Op0)) {
+ // FIXME: this is not true when we have external weak references!
+ // No offset can go from a global to a null pointer.
+ return Instruction::SetGT;
+ } else if (isa<ConstantPointerNull>(CE1Op0)) {
+ // If we are indexing from a null pointer, check to see if we have any
+ // non-zero indices.
+ for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
+ if (!CE1->getOperand(i)->isNullValue())
+ // Offsetting from null, must not be equal.
+ return Instruction::SetGT;
+ // Only zero indexes from null, must still be zero.
+ return Instruction::SetEQ;
+ }
+ // Otherwise, we can't really say if the first operand is null or not.
+ } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
+ if (isa<ConstantPointerNull>(CE1Op0)) {
+ // FIXME: This is not true with external weak references.
+ return Instruction::SetLT;
+ } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
+ if (CPR1 == CPR2) {
+ // If this is a getelementptr of the same global, then it must be
+ // different. Because the types must match, the getelementptr could
+ // only have at most one index, and because we fold getelementptr's
+ // with a single zero index, it must be nonzero.
+ assert(CE1->getNumOperands() == 2 &&
+ !CE1->getOperand(1)->isNullValue() &&
+ "Suprising getelementptr!");
+ return Instruction::SetGT;
+ } else {
+ // If they are different globals, we don't know what the value is,
+ // but they can't be equal.
+ return Instruction::SetNE;
+ }
+ }
+ } else {
+ const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
+ const Constant *CE2Op0 = CE2->getOperand(0);
+
+ // There are MANY other foldings that we could perform here. They will
+ // probably be added on demand, as they seem needed.
+ switch (CE2->getOpcode()) {
+ default: break;
+ case Instruction::GetElementPtr:
+ // By far the most common case to handle is when the base pointers are
+ // obviously to the same or different globals.
+ if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
+ if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
+ return Instruction::SetNE;
+ // Ok, we know that both getelementptr instructions are based on the
+ // same global. From this, we can precisely determine the relative
+ // ordering of the resultant pointers.
+ unsigned i = 1;
+
+ // Compare all of the operands the GEP's have in common.
+ gep_type_iterator GTI = gep_type_begin(CE1);
+ for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
+ ++i, ++GTI)
+ switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i),
+ GTI.getIndexedType())) {
+ case -1: return Instruction::SetLT;
+ case 1: return Instruction::SetGT;
+ case -2: return Instruction::BinaryOpsEnd;
+ }
+
+ // Ok, we ran out of things they have in common. If any leftovers
+ // are non-zero then we have a difference, otherwise we are equal.
+ for (; i < CE1->getNumOperands(); ++i)
+ if (!CE1->getOperand(i)->isNullValue())
+ if (isa<ConstantIntegral>(CE1->getOperand(i)))
+ return Instruction::SetGT;
+ else
+ return Instruction::BinaryOpsEnd; // Might be equal.
+
+ for (; i < CE2->getNumOperands(); ++i)
+ if (!CE2->getOperand(i)->isNullValue())
+ if (isa<ConstantIntegral>(CE2->getOperand(i)))
+ return Instruction::SetLT;
+ else
+ return Instruction::BinaryOpsEnd; // Might be equal.
+ return Instruction::SetEQ;
+ }
+ }
+ }
+
+ default:
+ break;
+ }
+ }
+
+ return Instruction::BinaryOpsEnd;
+}
+
+Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
+ const Constant *V1,
+ const Constant *V2) {
+ Constant *C = 0;
+ switch (Opcode) {
+ default: break;
+ case Instruction::Add: C = ConstRules::get(V1, V2).add(V1, V2); break;
+ case Instruction::Sub: C = ConstRules::get(V1, V2).sub(V1, V2); break;
+ case Instruction::Mul: C = ConstRules::get(V1, V2).mul(V1, V2); break;
+ case Instruction::Div: C = ConstRules::get(V1, V2).div(V1, V2); break;
+ case Instruction::Rem: C = ConstRules::get(V1, V2).rem(V1, V2); break;
+ case Instruction::And: C = ConstRules::get(V1, V2).op_and(V1, V2); break;
+ case Instruction::Or: C = ConstRules::get(V1, V2).op_or (V1, V2); break;
+ case Instruction::Xor: C = ConstRules::get(V1, V2).op_xor(V1, V2); break;
+ case Instruction::Shl: C = ConstRules::get(V1, V2).shl(V1, V2); break;
+ case Instruction::Shr: C = ConstRules::get(V1, V2).shr(V1, V2); break;
+ case Instruction::SetEQ: C = ConstRules::get(V1, V2).equalto(V1, V2); break;
+ case Instruction::SetLT: C = ConstRules::get(V1, V2).lessthan(V1, V2);break;
+ case Instruction::SetGT: C = ConstRules::get(V1, V2).lessthan(V2, V1);break;
+ case Instruction::SetNE: // V1 != V2 === !(V1 == V2)
+ C = ConstRules::get(V1, V2).equalto(V1, V2);
+ if (C) return ConstantExpr::getNot(C);
+ break;
+ case Instruction::SetLE: // V1 <= V2 === !(V2 < V1)
+ C = ConstRules::get(V1, V2).lessthan(V2, V1);
+ if (C) return ConstantExpr::getNot(C);
+ break;
+ case Instruction::SetGE: // V1 >= V2 === !(V1 < V2)
+ C = ConstRules::get(V1, V2).lessthan(V1, V2);
+ if (C) return ConstantExpr::getNot(C);
+ break;
+ }
+
+ // If we successfully folded the expression, return it now.
+ if (C) return C;
+
+ if (SetCondInst::isComparison(Opcode)) {
+ if (isa<UndefValue>(V1) || isa<UndefValue>(V2))
+ return UndefValue::get(Type::BoolTy);
+ switch (evaluateRelation(const_cast<Constant*>(V1),
+ const_cast<Constant*>(V2))) {
+ default: assert(0 && "Unknown relational!");
+ case Instruction::BinaryOpsEnd:
+ break; // Couldn't determine anything about these constants.
+ case Instruction::SetEQ: // We know the constants are equal!
+ // If we know the constants are equal, we can decide the result of this
+ // computation precisely.
+ return ConstantBool::get(Opcode == Instruction::SetEQ ||
+ Opcode == Instruction::SetLE ||
+ Opcode == Instruction::SetGE);
+ case Instruction::SetLT:
+ // If we know that V1 < V2, we can decide the result of this computation
+ // precisely.
+ return ConstantBool::get(Opcode == Instruction::SetLT ||
+ Opcode == Instruction::SetNE ||
+ Opcode == Instruction::SetLE);
+ case Instruction::SetGT:
+ // If we know that V1 > V2, we can decide the result of this computation
+ // precisely.
+ return ConstantBool::get(Opcode == Instruction::SetGT ||
+ Opcode == Instruction::SetNE ||
+ Opcode == Instruction::SetGE);
+ case Instruction::SetLE:
+ // If we know that V1 <= V2, we can only partially decide this relation.
+ if (Opcode == Instruction::SetGT) return ConstantBool::getFalse();
+ if (Opcode == Instruction::SetLT) return ConstantBool::getTrue();
+ break;
+
+ case Instruction::SetGE:
+ // If we know that V1 >= V2, we can only partially decide this relation.
+ if (Opcode == Instruction::SetLT) return ConstantBool::getFalse();
+ if (Opcode == Instruction::SetGT) return ConstantBool::getTrue();
+ break;
+
+ case Instruction::SetNE:
+ // If we know that V1 != V2, we can only partially decide this relation.
+ if (Opcode == Instruction::SetEQ) return ConstantBool::getFalse();
+ if (Opcode == Instruction::SetNE) return ConstantBool::getTrue();
+ break;
+ }
+ }
+
+ if (isa<UndefValue>(V1) || isa<UndefValue>(V2)) {
+ switch (Opcode) {
+ case Instruction::Add:
+ case Instruction::Sub:
+ case Instruction::Xor:
+ return UndefValue::get(V1->getType());
+
+ case Instruction::Mul:
+ case Instruction::And:
+ return Constant::getNullValue(V1->getType());
+ case Instruction::Div:
+ case Instruction::Rem:
+ if (!isa<UndefValue>(V2)) // undef/X -> 0
+ return Constant::getNullValue(V1->getType());
+ return const_cast<Constant*>(V2); // X/undef -> undef
+ case Instruction::Or: // X|undef -> -1
+ return ConstantInt::getAllOnesValue(V1->getType());
+ case Instruction::Shr:
+ if (!isa<UndefValue>(V2)) {
+ if (V1->getType()->isSigned())
+ return const_cast<Constant*>(V1); // undef >>s X -> undef
+ // undef >>u X -> 0
+ } else if (isa<UndefValue>(V1)) {
+ return const_cast<Constant*>(V1); // undef >> undef -> undef
+ } else {
+ if (V1->getType()->isSigned())
+ return const_cast<Constant*>(V1); // X >>s undef -> X
+ // X >>u undef -> 0
+ }
+ return Constant::getNullValue(V1->getType());
+
+ case Instruction::Shl:
+ // undef << X -> 0 X << undef -> 0
+ return Constant::getNullValue(V1->getType());
+ }
+ }
+
+ if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(V1)) {
+ if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
+ // There are many possible foldings we could do here. We should probably
+ // at least fold add of a pointer with an integer into the appropriate
+ // getelementptr. This will improve alias analysis a bit.
+
+
+
+
+ } else {
+ // Just implement a couple of simple identities.
+ switch (Opcode) {
+ case Instruction::Add:
+ if (V2->isNullValue()) return const_cast<Constant*>(V1); // X + 0 == X
+ break;
+ case Instruction::Sub:
+ if (V2->isNullValue()) return const_cast<Constant*>(V1); // X - 0 == X
+ break;
+ case Instruction::Mul:
+ if (V2->isNullValue()) return const_cast<Constant*>(V2); // X * 0 == 0
+ if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
+ if (CI->getZExtValue() == 1)
+ return const_cast<Constant*>(V1); // X * 1 == X
+ break;
+ case Instruction::Div:
+ if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
+ if (CI->getZExtValue() == 1)
+ return const_cast<Constant*>(V1); // X / 1 == X
+ break;
+ case Instruction::Rem:
+ if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
+ if (CI->getZExtValue() == 1)
+ return Constant::getNullValue(CI->getType()); // X % 1 == 0
+ break;
+ case Instruction::And:
+ if (cast<ConstantIntegral>(V2)->isAllOnesValue())
+ return const_cast<Constant*>(V1); // X & -1 == X
+ if (V2->isNullValue()) return const_cast<Constant*>(V2); // X & 0 == 0
+ if (CE1->getOpcode() == Instruction::Cast &&
+ isa<GlobalValue>(CE1->getOperand(0))) {
+ GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
+
+ // Functions are at least 4-byte aligned. If and'ing the address of a
+ // function with a constant < 4, fold it to zero.
+ if (const ConstantInt *CI = dyn_cast<ConstantInt>(V2))
+ if (CI->getZExtValue() < 4 && isa<Function>(CPR))
+ return Constant::getNullValue(CI->getType());
+ }
+ break;
+ case Instruction::Or:
+ if (V2->isNullValue()) return const_cast<Constant*>(V1); // X | 0 == X
+ if (cast<ConstantIntegral>(V2)->isAllOnesValue())
+ return const_cast<Constant*>(V2); // X | -1 == -1
+ break;
+ case Instruction::Xor:
+ if (V2->isNullValue()) return const_cast<Constant*>(V1); // X ^ 0 == X
+ break;
+ }
+ }
+
+ } else if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) {
+ // If V2 is a constant expr and V1 isn't, flop them around and fold the
+ // other way if possible.
+ switch (Opcode) {
+ case Instruction::Add:
+ case Instruction::Mul:
+ case Instruction::And:
+ case Instruction::Or:
+ case Instruction::Xor:
+ case Instruction::SetEQ:
+ case Instruction::SetNE:
+ // No change of opcode required.
+ return ConstantFoldBinaryInstruction(Opcode, V2, V1);
+
+ case Instruction::SetLT:
+ case Instruction::SetGT:
+ case Instruction::SetLE:
+ case Instruction::SetGE:
+ // Change the opcode as necessary to swap the operands.
+ Opcode = SetCondInst::getSwappedCondition((Instruction::BinaryOps)Opcode);
+ return ConstantFoldBinaryInstruction(Opcode, V2, V1);
+
+ case Instruction::Shl:
+ case Instruction::Shr:
+ case Instruction::Sub:
+ case Instruction::Div:
+ case Instruction::Rem:
+ default: // These instructions cannot be flopped around.
+ break;
+ }
+ }
+ return 0;
+}
+
+Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
+ const std::vector<Value*> &IdxList) {
+ if (IdxList.size() == 0 ||
+ (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue()))
+ return const_cast<Constant*>(C);
+
+ if (isa<UndefValue>(C)) {
+ const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList,
+ true);
+ assert(Ty != 0 && "Invalid indices for GEP!");
+ return UndefValue::get(PointerType::get(Ty));
+ }
+
+ Constant *Idx0 = cast<Constant>(IdxList[0]);
+ if (C->isNullValue()) {
+ bool isNull = true;
+ for (unsigned i = 0, e = IdxList.size(); i != e; ++i)
+ if (!cast<Constant>(IdxList[i])->isNullValue()) {
+ isNull = false;
+ break;
+ }
+ if (isNull) {
+ const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList,
+ true);
+ assert(Ty != 0 && "Invalid indices for GEP!");
+ return ConstantPointerNull::get(PointerType::get(Ty));
+ }
+
+ if (IdxList.size() == 1) {
+ const Type *ElTy = cast<PointerType>(C->getType())->getElementType();
+ if (uint32_t ElSize = ElTy->getPrimitiveSize()) {
+ // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm
+ // type, we can statically fold this.
+ Constant *R = ConstantInt::get(Type::UIntTy, ElSize);
+ R = ConstantExpr::getCast(R, Idx0->getType());
+ R = ConstantExpr::getMul(R, Idx0);
+ return ConstantExpr::getCast(R, C->getType());
+ }
+ }
+ }
+
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) {
+ // Combine Indices - If the source pointer to this getelementptr instruction
+ // is a getelementptr instruction, combine the indices of the two
+ // getelementptr instructions into a single instruction.
+ //
+ if (CE->getOpcode() == Instruction::GetElementPtr) {
+ const Type *LastTy = 0;
+ for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
+ I != E; ++I)
+ LastTy = *I;
+
+ if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
+ std::vector<Value*> NewIndices;
+ NewIndices.reserve(IdxList.size() + CE->getNumOperands());
+ for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
+ NewIndices.push_back(CE->getOperand(i));
+
+ // Add the last index of the source with the first index of the new GEP.
+ // Make sure to handle the case when they are actually different types.
+ Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
+ // Otherwise it must be an array.
+ if (!Idx0->isNullValue()) {
+ const Type *IdxTy = Combined->getType();
+ if (IdxTy != Idx0->getType()) IdxTy = Type::LongTy;
+ Combined =
+ ConstantExpr::get(Instruction::Add,
+ ConstantExpr::getCast(Idx0, IdxTy),
+ ConstantExpr::getCast(Combined, IdxTy));
+ }
+
+ NewIndices.push_back(Combined);
+ NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end());
+ return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices);
+ }
+ }
+
+ // Implement folding of:
+ // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
+ // long 0, long 0)
+ // To: int* getelementptr ([3 x int]* %X, long 0, long 0)
+ //
+ if (CE->getOpcode() == Instruction::Cast && IdxList.size() > 1 &&
+ Idx0->isNullValue())
+ if (const PointerType *SPT =
+ dyn_cast<PointerType>(CE->getOperand(0)->getType()))
+ if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
+ if (const ArrayType *CAT =
+ dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
+ if (CAT->getElementType() == SAT->getElementType())
+ return ConstantExpr::getGetElementPtr(
+ (Constant*)CE->getOperand(0), IdxList);
+ }
+ return 0;
+}
+