//===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the Constant class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_CONSTANT_H
#define LLVM_IR_CONSTANT_H
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
namespace llvm {
class APInt;
/// This is an important base class in LLVM. It provides the common facilities
/// of all constant values in an LLVM program. A constant is a value that is
/// immutable at runtime. Functions are constants because their address is
/// immutable. Same with global variables.
///
/// All constants share the capabilities provided in this class. All constants
/// can have a null value. They can have an operand list. Constants can be
/// simple (integer and floating point values), complex (arrays and structures),
/// or expression based (computations yielding a constant value composed of
/// only certain operators and other constant values).
///
/// Note that Constants are immutable (once created they never change)
/// and are fully shared by structural equivalence. This means that two
/// structurally equivalent constants will always have the same address.
/// Constants are created on demand as needed and never deleted: thus clients
/// don't have to worry about the lifetime of the objects.
/// LLVM Constant Representation
class Constant : public User {
protected:
Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
: User(ty, vty, Ops, NumOps) {}
~Constant() = default;
public:
void operator=(const Constant &) = delete;
Constant(const Constant &) = delete;
/// Return true if this is the value that would be returned by getNullValue.
bool isNullValue() const;
/// Returns true if the value is one.
bool isOneValue() const;
/// Return true if the value is not the one value, or,
/// for vectors, does not contain one value elements.
bool isNotOneValue() const;
/// Return true if this is the value that would be returned by
/// getAllOnesValue.
bool isAllOnesValue() const;
/// Return true if the value is what would be returned by
/// getZeroValueForNegation.
bool isNegativeZeroValue() const;
/// Return true if the value is negative zero or null value.
bool isZeroValue() const;
/// Return true if the value is not the smallest signed value, or,
/// for vectors, does not contain smallest signed value elements.
bool isNotMinSignedValue() const;
/// Return true if the value is the smallest signed value.
bool isMinSignedValue() const;
/// Return true if this is a finite and non-zero floating-point scalar
/// constant or a fixed width vector constant with all finite and non-zero
/// elements.
bool isFiniteNonZeroFP() const;
/// Return true if this is a normal (as opposed to denormal, infinity, nan,
/// or zero) floating-point scalar constant or a vector constant with all
/// normal elements. See APFloat::isNormal.
bool isNormalFP() const;
/// Return true if this scalar has an exact multiplicative inverse or this
/// vector has an exact multiplicative inverse for each element in the vector.
bool hasExactInverseFP() const;
/// Return true if this is a floating-point NaN constant or a vector
/// floating-point constant with all NaN elements.
bool isNaN() const;
/// Return true if this constant and a constant 'Y' are element-wise equal.
/// This is identical to just comparing the pointers, with the exception that
/// for vectors, if only one of the constants has an `undef` element in some
/// lane, the constants still match.
bool isElementWiseEqual(Value *Y) const;
/// Return true if this is a vector constant that includes any undef or
/// poison elements. Since it is impossible to inspect a scalable vector
/// element- wise at compile time, this function returns true only if the
/// entire vector is undef or poison.
bool containsUndefOrPoisonElement() const;
/// Return true if this is a vector constant that includes any poison
/// elements.
bool containsPoisonElement() const;
/// Return true if this is a vector constant that includes any strictly undef
/// (not poison) elements.
bool containsUndefElement() const;
/// Return true if this is a fixed width vector constant that includes
/// any constant expressions.
bool containsConstantExpression() const;
/// Return true if the value can vary between threads.
bool isThreadDependent() const;
/// Return true if the value is dependent on a dllimport variable.
bool isDLLImportDependent() const;
/// Return true if the constant has users other than constant expressions and
/// other dangling things.
bool isConstantUsed() const;
/// This method classifies the entry according to whether or not it may
/// generate a relocation entry (either static or dynamic). This must be
/// conservative, so if it might codegen to a relocatable entry, it should say
/// so.
///
/// FIXME: This really should not be in IR.
bool needsRelocation() const;
bool needsDynamicRelocation() const;
/// For aggregates (struct/array/vector) return the constant that corresponds
/// to the specified element if possible, or null if not. This can return null
/// if the element index is a ConstantExpr, if 'this' is a constant expr or
/// if the constant does not fit into an uint64_t.
Constant *getAggregateElement(unsigned Elt) const;
Constant *getAggregateElement(Constant *Elt) const;
/// If all elements of the vector constant have the same value, return that
/// value. Otherwise, return nullptr. Ignore undefined elements by setting
/// AllowUndefs to true.
Constant *getSplatValue(bool AllowUndefs = false) const;
/// If C is a constant integer then return its value, otherwise C must be a
/// vector of constant integers, all equal, and the common value is returned.
const APInt &getUniqueInteger() const;
/// Called if some element of this constant is no longer valid.
/// At this point only other constants may be on the use_list for this
/// constant. Any constants on our Use list must also be destroy'd. The
/// implementation must be sure to remove the constant from the list of
/// available cached constants. Implementations should implement
/// destroyConstantImpl to remove constants from any pools/maps they are
/// contained it.
void destroyConstant();
//// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const Value *V) {
static_assert(ConstantFirstVal == 0, "V->getValueID() >= ConstantFirstVal always succeeds");
return V->getValueID() <= ConstantLastVal;
}
/// This method is a special form of User::replaceUsesOfWith
/// (which does not work on constants) that does work
/// on constants. Basically this method goes through the trouble of building
/// a new constant that is equivalent to the current one, with all uses of
/// From replaced with uses of To. After this construction is completed, all
/// of the users of 'this' are replaced to use the new constant, and then
/// 'this' is deleted. In general, you should not call this method, instead,
/// use Value::replaceAllUsesWith, which automatically dispatches to this
/// method as needed.
///
void handleOperandChange(Value *, Value *);
static Constant *getNullValue(Type* Ty);
/// @returns the value for an integer or vector of integer constant of the
/// given type that has all its bits set to true.
/// Get the all ones value
static Constant *getAllOnesValue(Type* Ty);
/// Return the value for an integer or pointer constant, or a vector thereof,
/// with the given scalar value.
static Constant *getIntegerValue(Type *Ty, const APInt &V);
/// If there are any dead constant users dangling off of this constant, remove
/// them. This method is useful for clients that want to check to see if a
/// global is unused, but don't want to deal with potentially dead constants
/// hanging off of the globals.
void removeDeadConstantUsers() const;
/// Return true if the constant has exactly one live use.
///
/// This returns the same result as calling Value::hasOneUse after
/// Constant::removeDeadConstantUsers, but doesn't remove dead constants.
bool hasOneLiveUse() const;
/// Return true if the constant has no live uses.
///
/// This returns the same result as calling Value::use_empty after
/// Constant::removeDeadConstantUsers, but doesn't remove dead constants.
bool hasZeroLiveUses() const;
const Constant *stripPointerCasts() const {
return cast<Constant>(Value::stripPointerCasts());
}
Constant *stripPointerCasts() {
return const_cast<Constant*>(
static_cast<const Constant *>(this)->stripPointerCasts());
}
/// Try to replace undefined constant C or undefined elements in C with
/// Replacement. If no changes are made, the constant C is returned.
static Constant *replaceUndefsWith(Constant *C, Constant *Replacement);
/// Merges undefs of a Constant with another Constant, along with the
/// undefs already present. Other doesn't have to be the same type as C, but
/// both must either be scalars or vectors with the same element count. If no
/// changes are made, the constant C is returned.
static Constant *mergeUndefsWith(Constant *C, Constant *Other);
/// Return true if a constant is ConstantData or a ConstantAggregate or
/// ConstantExpr that contain only ConstantData.
bool isManifestConstant() const;
private:
enum PossibleRelocationsTy {
/// This constant requires no relocations. That is, it holds simple
/// constants (like integrals).
NoRelocation = 0,
/// This constant holds static relocations that can be resolved by the
/// static linker.
LocalRelocation = 1,
/// This constant holds dynamic relocations that the dynamic linker will
/// need to resolve.
GlobalRelocation = 2,
};
/// Determine what potential relocations may be needed by this constant.
PossibleRelocationsTy getRelocationInfo() const;
bool hasNLiveUses(unsigned N) const;
};
} // end namespace llvm
#endif // LLVM_IR_CONSTANT_H