llvm/lib/VMCore/ConstantFold.cpp
Chris Lattner 27287de06b Allow constant folding of GEP instructions, even if we don't do a whole lot yet.
Fold ConstExpr casts better
castToPointer shouldn't be forced to return a constantpointer


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5800 91177308-0d34-0410-b5e6-96231b3b80d8
2003-04-17 19:24:18 +00:00

558 lines
23 KiB
C++

//===- ConstantHandling.cpp - Implement ConstantHandling.h ----------------===//
//
// This file implements the various intrinsic operations, on constant values.
//
//===----------------------------------------------------------------------===//
#include "llvm/ConstantHandling.h"
#include "llvm/iPHINode.h"
#include "llvm/DerivedTypes.h"
#include <cmath>
AnnotationID ConstRules::AID(AnnotationManager::getID("opt::ConstRules",
&ConstRules::find));
// ConstantFoldInstruction - Attempt to constant fold the specified instruction.
// If successful, the constant result is returned, if not, null is returned.
//
Constant *ConstantFoldInstruction(Instruction *I) {
if (PHINode *PN = dyn_cast<PHINode>(I)) {
if (PN->getNumIncomingValues() == 0)
return Constant::getNullValue(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)
return 0; // Not all the same incoming constants...
// If we reach here, all incoming values are the same constant.
return Result;
}
Constant *Op0 = 0;
Constant *Op1 = 0;
if (I->getNumOperands() != 0) { // Get first operand if it's a constant...
Op0 = dyn_cast<Constant>(I->getOperand(0));
if (Op0 == 0) return 0; // Not a constant?, can't fold
if (I->getNumOperands() != 1) { // Get second operand if it's a constant...
Op1 = dyn_cast<Constant>(I->getOperand(1));
if (Op1 == 0) return 0; // Not a constant?, can't fold
}
}
switch (I->getOpcode()) {
case Instruction::Cast:
return ConstRules::get(*Op0)->castTo(Op0, I->getType());
case Instruction::Add: return *Op0 + *Op1;
case Instruction::Sub: return *Op0 - *Op1;
case Instruction::Mul: return *Op0 * *Op1;
case Instruction::Div: return *Op0 / *Op1;
case Instruction::Rem: return *Op0 % *Op1;
case Instruction::And: return *Op0 & *Op1;
case Instruction::Or: return *Op0 | *Op1;
case Instruction::Xor: return *Op0 ^ *Op1;
case Instruction::SetEQ: return *Op0 == *Op1;
case Instruction::SetNE: return *Op0 != *Op1;
case Instruction::SetLE: return *Op0 <= *Op1;
case Instruction::SetGE: return *Op0 >= *Op1;
case Instruction::SetLT: return *Op0 < *Op1;
case Instruction::SetGT: return *Op0 > *Op1;
case Instruction::Shl: return *Op0 << *Op1;
case Instruction::Shr: return *Op0 >> *Op1;
case Instruction::GetElementPtr: {
std::vector<Constant*> IdxList;
IdxList.reserve(I->getNumOperands()-1);
if (Op1) IdxList.push_back(Op1);
for (unsigned i = 2, e = I->getNumOperands(); i != e; ++i)
if (Constant *C = dyn_cast<Constant>(I->getOperand(i)))
IdxList.push_back(C);
else
return 0; // Non-constant operand
return ConstantFoldGetElementPtr(Op0, IdxList);
}
default:
return 0;
}
}
static unsigned getSize(const Type *Ty) {
unsigned S = Ty->getPrimitiveSize();
return S ? S : 8; // Treat pointers at 8 bytes
}
Constant *ConstantFoldCastInstruction(const Constant *V, const Type *DestTy) {
if (V->getType() == DestTy) return (Constant*)V;
if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
if (CE->getOpcode() == Instruction::Cast) {
Constant *Op = (Constant*)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->getType()->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);
}
}
return ConstRules::get(*V)->castTo(V, DestTy);
}
Constant *ConstantFoldBinaryInstruction(unsigned Opcode, const Constant *V1,
const Constant *V2) {
switch (Opcode) {
case Instruction::Add: return *V1 + *V2;
case Instruction::Sub: return *V1 - *V2;
case Instruction::Mul: return *V1 * *V2;
case Instruction::Div: return *V1 / *V2;
case Instruction::Rem: return *V1 % *V2;
case Instruction::And: return *V1 & *V2;
case Instruction::Or: return *V1 | *V2;
case Instruction::Xor: return *V1 ^ *V2;
case Instruction::SetEQ: return *V1 == *V2;
case Instruction::SetNE: return *V1 != *V2;
case Instruction::SetLE: return *V1 <= *V2;
case Instruction::SetGE: return *V1 >= *V2;
case Instruction::SetLT: return *V1 < *V2;
case Instruction::SetGT: return *V1 > *V2;
}
return 0;
}
Constant *ConstantFoldShiftInstruction(unsigned Opcode, const Constant *V1,
const Constant *V2) {
switch (Opcode) {
case Instruction::Shl: return *V1 << *V2;
case Instruction::Shr: return *V1 >> *V2;
default: return 0;
}
}
Constant *ConstantFoldGetElementPtr(const Constant *C,
const std::vector<Constant*> &IdxList) {
if (IdxList.size() == 0 ||
(IdxList.size() == 1 && IdxList[0]->isNullValue()))
return const_cast<Constant*>(C);
// If C is null and all idx's are null, return null of the right type.
// FIXME: Implement folding of GEP constant exprs the same as instcombine does
return 0;
}
//===----------------------------------------------------------------------===//
// TemplateRules Class
//===----------------------------------------------------------------------===//
//
// TemplateRules - Implement a subclass of ConstRules that provides all
// operations as noops. All other rules classes inherit from this class so
// that if functionality is needed in the future, it can simply be added here
// and to ConstRules without changing anything else...
//
// This class also provides subclasses with typesafe implementations of methods
// so that don't have to do type casting.
//
template<class ArgType, class SubClassName>
class TemplateRules : public ConstRules {
//===--------------------------------------------------------------------===//
// Redirecting functions that cast to the appropriate types
//===--------------------------------------------------------------------===//
virtual Constant *add(const Constant *V1, const Constant *V2) const {
return SubClassName::Add((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *sub(const Constant *V1, const Constant *V2) const {
return SubClassName::Sub((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *mul(const Constant *V1, const Constant *V2) const {
return SubClassName::Mul((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *div(const Constant *V1, const Constant *V2) const {
return SubClassName::Div((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *rem(const Constant *V1, const Constant *V2) const {
return SubClassName::Rem((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *op_and(const Constant *V1, const Constant *V2) const {
return SubClassName::And((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *op_or(const Constant *V1, const Constant *V2) const {
return SubClassName::Or((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *op_xor(const Constant *V1, const Constant *V2) const {
return SubClassName::Xor((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *shl(const Constant *V1, const Constant *V2) const {
return SubClassName::Shl((const ArgType *)V1, (const ArgType *)V2);
}
virtual Constant *shr(const Constant *V1, const Constant *V2) const {
return SubClassName::Shr((const ArgType *)V1, (const ArgType *)V2);
}
virtual ConstantBool *lessthan(const Constant *V1,
const Constant *V2) const {
return SubClassName::LessThan((const ArgType *)V1, (const ArgType *)V2);
}
// Casting operators. ick
virtual ConstantBool *castToBool(const Constant *V) const {
return SubClassName::CastToBool((const ArgType*)V);
}
virtual ConstantSInt *castToSByte(const Constant *V) const {
return SubClassName::CastToSByte((const ArgType*)V);
}
virtual ConstantUInt *castToUByte(const Constant *V) const {
return SubClassName::CastToUByte((const ArgType*)V);
}
virtual ConstantSInt *castToShort(const Constant *V) const {
return SubClassName::CastToShort((const ArgType*)V);
}
virtual ConstantUInt *castToUShort(const Constant *V) const {
return SubClassName::CastToUShort((const ArgType*)V);
}
virtual ConstantSInt *castToInt(const Constant *V) const {
return SubClassName::CastToInt((const ArgType*)V);
}
virtual ConstantUInt *castToUInt(const Constant *V) const {
return SubClassName::CastToUInt((const ArgType*)V);
}
virtual ConstantSInt *castToLong(const Constant *V) const {
return SubClassName::CastToLong((const ArgType*)V);
}
virtual ConstantUInt *castToULong(const Constant *V) const {
return SubClassName::CastToULong((const ArgType*)V);
}
virtual ConstantFP *castToFloat(const Constant *V) const {
return SubClassName::CastToFloat((const ArgType*)V);
}
virtual ConstantFP *castToDouble(const Constant *V) const {
return SubClassName::CastToDouble((const ArgType*)V);
}
virtual Constant *castToPointer(const Constant *V,
const PointerType *Ty) const {
return SubClassName::CastToPointer((const ArgType*)V, Ty);
}
//===--------------------------------------------------------------------===//
// Default "noop" implementations
//===--------------------------------------------------------------------===//
static Constant *Add(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Sub(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Mul(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Div(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Rem(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *And(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Or (const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Xor(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Shl(const ArgType *V1, const ArgType *V2) { return 0; }
static Constant *Shr(const ArgType *V1, const ArgType *V2) { return 0; }
static ConstantBool *LessThan(const ArgType *V1, const ArgType *V2) {
return 0;
}
// Casting operators. ick
static ConstantBool *CastToBool (const Constant *V) { return 0; }
static ConstantSInt *CastToSByte (const Constant *V) { return 0; }
static ConstantUInt *CastToUByte (const Constant *V) { return 0; }
static ConstantSInt *CastToShort (const Constant *V) { return 0; }
static ConstantUInt *CastToUShort(const Constant *V) { return 0; }
static ConstantSInt *CastToInt (const Constant *V) { return 0; }
static ConstantUInt *CastToUInt (const Constant *V) { return 0; }
static ConstantSInt *CastToLong (const Constant *V) { return 0; }
static ConstantUInt *CastToULong (const Constant *V) { return 0; }
static ConstantFP *CastToFloat (const Constant *V) { return 0; }
static ConstantFP *CastToDouble(const Constant *V) { return 0; }
static Constant *CastToPointer(const Constant *,
const PointerType *) {return 0;}
};
//===----------------------------------------------------------------------===//
// EmptyRules Class
//===----------------------------------------------------------------------===//
//
// EmptyRules provides a concrete base class of ConstRules that does nothing
//
struct EmptyRules : public TemplateRules<Constant, EmptyRules> {
};
//===----------------------------------------------------------------------===//
// BoolRules Class
//===----------------------------------------------------------------------===//
//
// BoolRules provides a concrete base class of ConstRules for the 'bool' type.
//
struct BoolRules : public TemplateRules<ConstantBool, BoolRules> {
static ConstantBool *LessThan(const ConstantBool *V1, const ConstantBool *V2){
return ConstantBool::get(V1->getValue() < V2->getValue());
}
static Constant *And(const ConstantBool *V1, const ConstantBool *V2) {
return ConstantBool::get(V1->getValue() & V2->getValue());
}
static Constant *Or(const ConstantBool *V1, const ConstantBool *V2) {
return ConstantBool::get(V1->getValue() | V2->getValue());
}
static Constant *Xor(const ConstantBool *V1, const ConstantBool *V2) {
return ConstantBool::get(V1->getValue() ^ V2->getValue());
}
};
//===----------------------------------------------------------------------===//
// PointerRules Class
//===----------------------------------------------------------------------===//
//
// PointerRules provides a concrete base class of ConstRules for pointer types
//
struct PointerRules : public TemplateRules<ConstantPointer, PointerRules> {
static ConstantBool *CastToBool (const Constant *V) {
if (V->isNullValue()) return ConstantBool::False;
return 0; // Can't const prop other types of pointers
}
static ConstantSInt *CastToSByte (const Constant *V) {
if (V->isNullValue()) return ConstantSInt::get(Type::SByteTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantUInt *CastToUByte (const Constant *V) {
if (V->isNullValue()) return ConstantUInt::get(Type::UByteTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantSInt *CastToShort (const Constant *V) {
if (V->isNullValue()) return ConstantSInt::get(Type::ShortTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantUInt *CastToUShort(const Constant *V) {
if (V->isNullValue()) return ConstantUInt::get(Type::UShortTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantSInt *CastToInt (const Constant *V) {
if (V->isNullValue()) return ConstantSInt::get(Type::IntTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantUInt *CastToUInt (const Constant *V) {
if (V->isNullValue()) return ConstantUInt::get(Type::UIntTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantSInt *CastToLong (const Constant *V) {
if (V->isNullValue()) return ConstantSInt::get(Type::LongTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantUInt *CastToULong (const Constant *V) {
if (V->isNullValue()) return ConstantUInt::get(Type::ULongTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantFP *CastToFloat (const Constant *V) {
if (V->isNullValue()) return ConstantFP::get(Type::FloatTy, 0);
return 0; // Can't const prop other types of pointers
}
static ConstantFP *CastToDouble(const Constant *V) {
if (V->isNullValue()) return ConstantFP::get(Type::DoubleTy, 0);
return 0; // Can't const prop other types of pointers
}
static Constant *CastToPointer(const ConstantPointer *V,
const PointerType *PTy) {
if (V->getType() == PTy)
return const_cast<ConstantPointer*>(V); // Allow cast %PTy %ptr to %PTy
if (V->isNullValue())
return ConstantPointerNull::get(PTy);
return 0; // Can't const prop other types of pointers
}
};
//===----------------------------------------------------------------------===//
// DirectRules Class
//===----------------------------------------------------------------------===//
//
// DirectRules provides a concrete base classes of ConstRules for a variety of
// different types. This allows the C++ compiler to automatically generate our
// constant handling operations in a typesafe and accurate manner.
//
template<class ConstantClass, class BuiltinType, Type **Ty, class SuperClass>
struct DirectRules : public TemplateRules<ConstantClass, SuperClass> {
static Constant *Add(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() + (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Sub(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() - (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Mul(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() * (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Div(const ConstantClass *V1, const ConstantClass *V2) {
if (V2->isNullValue()) return 0;
BuiltinType R = (BuiltinType)V1->getValue() / (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static ConstantBool *LessThan(const ConstantClass *V1,
const ConstantClass *V2) {
bool R = (BuiltinType)V1->getValue() < (BuiltinType)V2->getValue();
return ConstantBool::get(R);
}
static Constant *CastToPointer(const ConstantClass *V,
const PointerType *PTy) {
if (V->isNullValue()) // Is it a FP or Integral null value?
return ConstantPointerNull::get(PTy);
return 0; // Can't const prop other types of pointers
}
// Casting operators. ick
#define DEF_CAST(TYPE, CLASS, CTYPE) \
static CLASS *CastTo##TYPE (const ConstantClass *V) { \
return CLASS::get(Type::TYPE##Ty, (CTYPE)(BuiltinType)V->getValue()); \
}
DEF_CAST(Bool , ConstantBool, bool)
DEF_CAST(SByte , ConstantSInt, signed char)
DEF_CAST(UByte , ConstantUInt, unsigned char)
DEF_CAST(Short , ConstantSInt, signed short)
DEF_CAST(UShort, ConstantUInt, unsigned short)
DEF_CAST(Int , ConstantSInt, signed int)
DEF_CAST(UInt , ConstantUInt, unsigned int)
DEF_CAST(Long , ConstantSInt, int64_t)
DEF_CAST(ULong , ConstantUInt, uint64_t)
DEF_CAST(Float , ConstantFP , float)
DEF_CAST(Double, ConstantFP , double)
#undef DEF_CAST
};
//===----------------------------------------------------------------------===//
// DirectIntRules Class
//===----------------------------------------------------------------------===//
//
// DirectIntRules provides implementations of functions that are valid on
// integer types, but not all types in general.
//
template <class ConstantClass, class BuiltinType, Type **Ty>
struct DirectIntRules
: public DirectRules<ConstantClass, BuiltinType, Ty,
DirectIntRules<ConstantClass, BuiltinType, Ty> > {
static Constant *Rem(const ConstantClass *V1,
const ConstantClass *V2) {
if (V2->isNullValue()) return 0;
BuiltinType R = (BuiltinType)V1->getValue() % (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *And(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() & (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Or(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() | (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Xor(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() ^ (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Shl(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() << (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
static Constant *Shr(const ConstantClass *V1, const ConstantClass *V2) {
BuiltinType R = (BuiltinType)V1->getValue() >> (BuiltinType)V2->getValue();
return ConstantClass::get(*Ty, R);
}
};
//===----------------------------------------------------------------------===//
// DirectFPRules Class
//===----------------------------------------------------------------------===//
//
// DirectFPRules provides implementations of functions that are valid on
// floating point types, but not all types in general.
//
template <class ConstantClass, class BuiltinType, Type **Ty>
struct DirectFPRules
: public DirectRules<ConstantClass, BuiltinType, Ty,
DirectFPRules<ConstantClass, BuiltinType, Ty> > {
static Constant *Rem(const ConstantClass *V1, const ConstantClass *V2) {
if (V2->isNullValue()) return 0;
BuiltinType Result = std::fmod((BuiltinType)V1->getValue(),
(BuiltinType)V2->getValue());
return ConstantClass::get(*Ty, Result);
}
};
//===----------------------------------------------------------------------===//
// DirectRules Subclasses
//===----------------------------------------------------------------------===//
//
// Given the DirectRules class we can now implement lots of types with little
// code. Thank goodness C++ compilers are great at stomping out layers of
// templates... can you imagine having to do this all by hand? (/me is lazy :)
//
// ConstRules::find - Return the constant rules that take care of the specified
// type.
//
Annotation *ConstRules::find(AnnotationID AID, const Annotable *TyA, void *) {
assert(AID == ConstRules::AID && "Bad annotation for factory!");
const Type *Ty = cast<Type>((const Value*)TyA);
switch (Ty->getPrimitiveID()) {
case Type::BoolTyID: return new BoolRules();
case Type::PointerTyID: return new PointerRules();
case Type::SByteTyID:
return new DirectIntRules<ConstantSInt, signed char , &Type::SByteTy>();
case Type::UByteTyID:
return new DirectIntRules<ConstantUInt, unsigned char , &Type::UByteTy>();
case Type::ShortTyID:
return new DirectIntRules<ConstantSInt, signed short, &Type::ShortTy>();
case Type::UShortTyID:
return new DirectIntRules<ConstantUInt, unsigned short, &Type::UShortTy>();
case Type::IntTyID:
return new DirectIntRules<ConstantSInt, signed int , &Type::IntTy>();
case Type::UIntTyID:
return new DirectIntRules<ConstantUInt, unsigned int , &Type::UIntTy>();
case Type::LongTyID:
return new DirectIntRules<ConstantSInt, int64_t , &Type::LongTy>();
case Type::ULongTyID:
return new DirectIntRules<ConstantUInt, uint64_t , &Type::ULongTy>();
case Type::FloatTyID:
return new DirectFPRules<ConstantFP , float , &Type::FloatTy>();
case Type::DoubleTyID:
return new DirectFPRules<ConstantFP , double , &Type::DoubleTy>();
default:
return new EmptyRules();
}
}