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| //===- FixedPoint.cpp - 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 implementation for the fixed point number interface.
//
//===----------------------------------------------------------------------===//
#include "clang/Basic/FixedPoint.h"
namespace clang {
APFixedPoint APFixedPoint::convert(const FixedPointSemantics &DstSema,
bool *Overflow) const {
llvm::APSInt NewVal = Val;
unsigned DstWidth = DstSema.getWidth();
unsigned DstScale = DstSema.getScale();
bool Upscaling = DstScale > getScale();
if (Overflow)
*Overflow = false;
if (Upscaling) {
NewVal = NewVal.extend(NewVal.getBitWidth() + DstScale - getScale());
NewVal <<= (DstScale - getScale());
} else {
NewVal >>= (getScale() - DstScale);
}
auto Mask = llvm::APInt::getBitsSetFrom(
NewVal.getBitWidth(),
std::min(DstScale + DstSema.getIntegralBits(), NewVal.getBitWidth()));
llvm::APInt Masked(NewVal & Mask);
// Change in the bits above the sign
if (!(Masked == Mask || Masked == 0)) {
// Found overflow in the bits above the sign
if (DstSema.isSaturated())
NewVal = NewVal.isNegative() ? Mask : ~Mask;
else if (Overflow)
*Overflow = true;
}
// If the dst semantics are unsigned, but our value is signed and negative, we
// clamp to zero.
if (!DstSema.isSigned() && NewVal.isSigned() && NewVal.isNegative()) {
// Found negative overflow for unsigned result
if (DstSema.isSaturated())
NewVal = 0;
else if (Overflow)
*Overflow = true;
}
NewVal = NewVal.extOrTrunc(DstWidth);
NewVal.setIsSigned(DstSema.isSigned());
return APFixedPoint(NewVal, DstSema);
}
int APFixedPoint::compare(const APFixedPoint &Other) const {
llvm::APSInt ThisVal = getValue();
llvm::APSInt OtherVal = Other.getValue();
bool ThisSigned = Val.isSigned();
bool OtherSigned = OtherVal.isSigned();
unsigned OtherScale = Other.getScale();
unsigned OtherWidth = OtherVal.getBitWidth();
unsigned CommonWidth = std::max(Val.getBitWidth(), OtherWidth);
// Prevent overflow in the event the widths are the same but the scales differ
CommonWidth += getScale() >= OtherScale ? getScale() - OtherScale
: OtherScale - getScale();
ThisVal = ThisVal.extOrTrunc(CommonWidth);
OtherVal = OtherVal.extOrTrunc(CommonWidth);
unsigned CommonScale = std::max(getScale(), OtherScale);
ThisVal = ThisVal.shl(CommonScale - getScale());
OtherVal = OtherVal.shl(CommonScale - OtherScale);
if (ThisSigned && OtherSigned) {
if (ThisVal.sgt(OtherVal))
return 1;
else if (ThisVal.slt(OtherVal))
return -1;
} else if (!ThisSigned && !OtherSigned) {
if (ThisVal.ugt(OtherVal))
return 1;
else if (ThisVal.ult(OtherVal))
return -1;
} else if (ThisSigned && !OtherSigned) {
if (ThisVal.isSignBitSet())
return -1;
else if (ThisVal.ugt(OtherVal))
return 1;
else if (ThisVal.ult(OtherVal))
return -1;
} else {
// !ThisSigned && OtherSigned
if (OtherVal.isSignBitSet())
return 1;
else if (ThisVal.ugt(OtherVal))
return 1;
else if (ThisVal.ult(OtherVal))
return -1;
}
return 0;
}
APFixedPoint APFixedPoint::getMax(const FixedPointSemantics &Sema) {
bool IsUnsigned = !Sema.isSigned();
auto Val = llvm::APSInt::getMaxValue(Sema.getWidth(), IsUnsigned);
if (IsUnsigned && Sema.hasUnsignedPadding())
Val = Val.lshr(1);
return APFixedPoint(Val, Sema);
}
APFixedPoint APFixedPoint::getMin(const FixedPointSemantics &Sema) {
auto Val = llvm::APSInt::getMinValue(Sema.getWidth(), !Sema.isSigned());
return APFixedPoint(Val, Sema);
}
FixedPointSemantics FixedPointSemantics::getCommonSemantics(
const FixedPointSemantics &Other) const {
unsigned CommonScale = std::max(getScale(), Other.getScale());
unsigned CommonWidth =
std::max(getIntegralBits(), Other.getIntegralBits()) + CommonScale;
bool ResultIsSigned = isSigned() || Other.isSigned();
bool ResultIsSaturated = isSaturated() || Other.isSaturated();
bool ResultHasUnsignedPadding = false;
if (!ResultIsSigned) {
// Both are unsigned.
ResultHasUnsignedPadding = hasUnsignedPadding() &&
Other.hasUnsignedPadding() && !ResultIsSaturated;
}
// If the result is signed, add an extra bit for the sign. Otherwise, if it is
// unsigned and has unsigned padding, we only need to add the extra padding
// bit back if we are not saturating.
if (ResultIsSigned || ResultHasUnsignedPadding)
CommonWidth++;
return FixedPointSemantics(CommonWidth, CommonScale, ResultIsSigned,
ResultIsSaturated, ResultHasUnsignedPadding);
}
APFixedPoint APFixedPoint::add(const APFixedPoint &Other,
bool *Overflow) const {
auto CommonFXSema = Sema.getCommonSemantics(Other.getSemantics());
APFixedPoint ConvertedThis = convert(CommonFXSema);
APFixedPoint ConvertedOther = Other.convert(CommonFXSema);
llvm::APSInt ThisVal = ConvertedThis.getValue();
llvm::APSInt OtherVal = ConvertedOther.getValue();
bool Overflowed = false;
llvm::APSInt Result;
if (CommonFXSema.isSaturated()) {
Result = CommonFXSema.isSigned() ? ThisVal.sadd_sat(OtherVal)
: ThisVal.uadd_sat(OtherVal);
} else {
Result = ThisVal.isSigned() ? ThisVal.sadd_ov(OtherVal, Overflowed)
: ThisVal.uadd_ov(OtherVal, Overflowed);
}
if (Overflow)
*Overflow = Overflowed;
return APFixedPoint(Result, CommonFXSema);
}
void APFixedPoint::toString(llvm::SmallVectorImpl<char> &Str) const {
llvm::APSInt Val = getValue();
unsigned Scale = getScale();
if (Val.isSigned() && Val.isNegative() && Val != -Val) {
Val = -Val;
Str.push_back('-');
}
llvm::APSInt IntPart = Val >> Scale;
// Add 4 digits to hold the value after multiplying 10 (the radix)
unsigned Width = Val.getBitWidth() + 4;
llvm::APInt FractPart = Val.zextOrTrunc(Scale).zext(Width);
llvm::APInt FractPartMask = llvm::APInt::getAllOnesValue(Scale).zext(Width);
llvm::APInt RadixInt = llvm::APInt(Width, 10);
IntPart.toString(Str, /*Radix=*/10);
Str.push_back('.');
do {
(FractPart * RadixInt)
.lshr(Scale)
.toString(Str, /*Radix=*/10, Val.isSigned());
FractPart = (FractPart * RadixInt) & FractPartMask;
} while (FractPart != 0);
}
APFixedPoint APFixedPoint::negate(bool *Overflow) const {
if (!isSaturated()) {
if (Overflow)
*Overflow =
(!isSigned() && Val != 0) || (isSigned() && Val.isMinSignedValue());
return APFixedPoint(-Val, Sema);
}
// We never overflow for saturation
if (Overflow)
*Overflow = false;
if (isSigned())
return Val.isMinSignedValue() ? getMax(Sema) : APFixedPoint(-Val, Sema);
else
return APFixedPoint(Sema);
}
llvm::APSInt APFixedPoint::convertToInt(unsigned DstWidth, bool DstSign,
bool *Overflow) const {
llvm::APSInt Result = getIntPart();
unsigned SrcWidth = getWidth();
llvm::APSInt DstMin = llvm::APSInt::getMinValue(DstWidth, !DstSign);
llvm::APSInt DstMax = llvm::APSInt::getMaxValue(DstWidth, !DstSign);
if (SrcWidth < DstWidth) {
Result = Result.extend(DstWidth);
} else if (SrcWidth > DstWidth) {
DstMin = DstMin.extend(SrcWidth);
DstMax = DstMax.extend(SrcWidth);
}
if (Overflow) {
if (Result.isSigned() && !DstSign) {
*Overflow = Result.isNegative() || Result.ugt(DstMax);
} else if (Result.isUnsigned() && DstSign) {
*Overflow = Result.ugt(DstMax);
} else {
*Overflow = Result < DstMin || Result > DstMax;
}
}
Result.setIsSigned(DstSign);
return Result.extOrTrunc(DstWidth);
}
APFixedPoint APFixedPoint::getFromIntValue(const llvm::APSInt &Value,
const FixedPointSemantics &DstFXSema,
bool *Overflow) {
FixedPointSemantics IntFXSema = FixedPointSemantics::GetIntegerSemantics(
Value.getBitWidth(), Value.isSigned());
return APFixedPoint(Value, IntFXSema).convert(DstFXSema, Overflow);
}
} // namespace clang
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