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//===- FixedPoint.h - Fixed point constant handling -------------*- 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
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Defines the fixed point number interface.
/// This is a class for abstracting various operations performed on fixed point
/// types described in ISO/IEC JTC1 SC22 WG14 N1169 starting at clause 4.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_BASIC_FIXEDPOINT_H
#define LLVM_CLANG_BASIC_FIXEDPOINT_H
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/raw_ostream.h"
namespace clang {
class ASTContext;
class QualType;
/// The fixed point semantics work similarly to llvm::fltSemantics. The width
/// specifies the whole bit width of the underlying scaled integer (with padding
/// if any). The scale represents the number of fractional bits in this type.
/// When HasUnsignedPadding is true and this type is signed, the first bit
/// in the value this represents is treaded as padding.
class FixedPointSemantics {
public:
FixedPointSemantics(unsigned Width, unsigned Scale, bool IsSigned,
bool IsSaturated, bool HasUnsignedPadding)
: Width(Width), Scale(Scale), IsSigned(IsSigned),
IsSaturated(IsSaturated), HasUnsignedPadding(HasUnsignedPadding) {
assert(Width >= Scale && "Not enough room for the scale");
assert(!(IsSigned && HasUnsignedPadding) &&
"Cannot have unsigned padding on a signed type.");
}
unsigned getWidth() const { return Width; }
unsigned getScale() const { return Scale; }
bool isSigned() const { return IsSigned; }
bool isSaturated() const { return IsSaturated; }
bool hasUnsignedPadding() const { return HasUnsignedPadding; }
void setSaturated(bool Saturated) { IsSaturated = Saturated; }
/// Return the number of integral bits represented by these semantics. These
/// are separate from the fractional bits and do not include the sign or
/// padding bit.
unsigned getIntegralBits() const {
if (IsSigned || (!IsSigned && HasUnsignedPadding))
return Width - Scale - 1;
else
return Width - Scale;
}
/// Return the FixedPointSemantics that allows for calculating the full
/// precision semantic that can precisely represent the precision and ranges
/// of both input values. This does not compute the resulting semantics for a
/// given binary operation.
FixedPointSemantics
getCommonSemantics(const FixedPointSemantics &Other) const;
/// Return the FixedPointSemantics for an integer type.
static FixedPointSemantics GetIntegerSemantics(unsigned Width,
bool IsSigned) {
return FixedPointSemantics(Width, /*Scale=*/0, IsSigned,
/*IsSaturated=*/false,
/*HasUnsignedPadding=*/false);
}
private:
unsigned Width;
unsigned Scale;
bool IsSigned;
bool IsSaturated;
bool HasUnsignedPadding;
};
/// The APFixedPoint class works similarly to APInt/APSInt in that it is a
/// functional replacement for a scaled integer. It is meant to replicate the
/// fixed point types proposed in ISO/IEC JTC1 SC22 WG14 N1169. The class carries
/// info about the fixed point type's width, sign, scale, and saturation, and
/// provides different operations that would normally be performed on fixed point
/// types.
///
/// Semantically this does not represent any existing C type other than fixed
/// point types and should eventually be moved to LLVM if fixed point types gain
/// native IR support.
class APFixedPoint {
public:
APFixedPoint(const llvm::APInt &Val, const FixedPointSemantics &Sema)
: Val(Val, !Sema.isSigned()), Sema(Sema) {
assert(Val.getBitWidth() == Sema.getWidth() &&
"The value should have a bit width that matches the Sema width");
}
APFixedPoint(uint64_t Val, const FixedPointSemantics &Sema)
: APFixedPoint(llvm::APInt(Sema.getWidth(), Val, Sema.isSigned()),
Sema) {}
// Zero initialization.
APFixedPoint(const FixedPointSemantics &Sema) : APFixedPoint(0, Sema) {}
llvm::APSInt getValue() const { return llvm::APSInt(Val, !Sema.isSigned()); }
inline unsigned getWidth() const { return Sema.getWidth(); }
inline unsigned getScale() const { return Sema.getScale(); }
inline bool isSaturated() const { return Sema.isSaturated(); }
inline bool isSigned() const { return Sema.isSigned(); }
inline bool hasPadding() const { return Sema.hasUnsignedPadding(); }
FixedPointSemantics getSemantics() const { return Sema; }
bool getBoolValue() const { return Val.getBoolValue(); }
// Convert this number to match the semantics provided. If the overflow
// parameter is provided, set this value to true or false to indicate if this
// operation results in an overflow.
APFixedPoint convert(const FixedPointSemantics &DstSema,
bool *Overflow = nullptr) const;
// Perform binary operations on a fixed point type. The resulting fixed point
// value will be in the common, full precision semantics that can represent
// the precision and ranges os both input values. See convert() for an
// explanation of the Overflow parameter.
APFixedPoint add(const APFixedPoint &Other, bool *Overflow = nullptr) const;
/// Perform a unary negation (-X) on this fixed point type, taking into
/// account saturation if applicable.
APFixedPoint negate(bool *Overflow = nullptr) const;
APFixedPoint shr(unsigned Amt) const {
return APFixedPoint(Val >> Amt, Sema);
}
APFixedPoint shl(unsigned Amt) const {
return APFixedPoint(Val << Amt, Sema);
}
/// Return the integral part of this fixed point number, rounded towards
/// zero. (-2.5k -> -2)
llvm::APSInt getIntPart() const {
if (Val < 0 && Val != -Val) // Cover the case when we have the min val
return -(-Val >> getScale());
else
return Val >> getScale();
}
/// Return the integral part of this fixed point number, rounded towards
/// zero. The value is stored into an APSInt with the provided width and sign.
/// If the overflow parameter is provided, and the integral value is not able
/// to be fully stored in the provided width and sign, the overflow parameter
/// is set to true.
///
/// If the overflow parameter is provided, set this value to true or false to
/// indicate if this operation results in an overflow.
llvm::APSInt convertToInt(unsigned DstWidth, bool DstSign,
bool *Overflow = nullptr) const;
void toString(llvm::SmallVectorImpl<char> &Str) const;
std::string toString() const {
llvm::SmallString<40> S;
toString(S);
return S.str();
}
// If LHS > RHS, return 1. If LHS == RHS, return 0. If LHS < RHS, return -1.
int compare(const APFixedPoint &Other) const;
bool operator==(const APFixedPoint &Other) const {
return compare(Other) == 0;
}
bool operator!=(const APFixedPoint &Other) const {
return compare(Other) != 0;
}
bool operator>(const APFixedPoint &Other) const { return compare(Other) > 0; }
bool operator<(const APFixedPoint &Other) const { return compare(Other) < 0; }
bool operator>=(const APFixedPoint &Other) const {
return compare(Other) >= 0;
}
bool operator<=(const APFixedPoint &Other) const {
return compare(Other) <= 0;
}
static APFixedPoint getMax(const FixedPointSemantics &Sema);
static APFixedPoint getMin(const FixedPointSemantics &Sema);
/// Create an APFixedPoint with a value equal to that of the provided integer,
/// and in the same semantics as the provided target semantics. If the value
/// is not able to fit in the specified fixed point semantics, and the
/// overflow parameter is provided, it is set to true.
static APFixedPoint getFromIntValue(const llvm::APSInt &Value,
const FixedPointSemantics &DstFXSema,
bool *Overflow = nullptr);
private:
llvm::APSInt Val;
FixedPointSemantics Sema;
};
inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
const APFixedPoint &FX) {
OS << FX.toString();
return OS;
}
} // namespace clang
#endif
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