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FixedPoint.h
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1 //===- FixedPoint.h - Fixed point constant handling -------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 /// \file
10 /// Defines the fixed point number interface.
11 /// This is a class for abstracting various operations performed on fixed point
12 /// types described in ISO/IEC JTC1 SC22 WG14 N1169 starting at clause 4.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CLANG_BASIC_FIXEDPOINT_H
17 #define LLVM_CLANG_BASIC_FIXEDPOINT_H
18 
19 #include "llvm/ADT/APSInt.h"
20 #include "llvm/ADT/SmallString.h"
21 #include "llvm/Support/raw_ostream.h"
22 
23 namespace clang {
24 
25 class ASTContext;
26 class QualType;
27 
28 /// The fixed point semantics work similarly to llvm::fltSemantics. The width
29 /// specifies the whole bit width of the underlying scaled integer (with padding
30 /// if any). The scale represents the number of fractional bits in this type.
31 /// When HasUnsignedPadding is true and this type is signed, the first bit
32 /// in the value this represents is treaded as padding.
34 public:
35  FixedPointSemantics(unsigned Width, unsigned Scale, bool IsSigned,
36  bool IsSaturated, bool HasUnsignedPadding)
37  : Width(Width), Scale(Scale), IsSigned(IsSigned),
38  IsSaturated(IsSaturated), HasUnsignedPadding(HasUnsignedPadding) {
39  assert(Width >= Scale && "Not enough room for the scale");
40  assert(!(IsSigned && HasUnsignedPadding) &&
41  "Cannot have unsigned padding on a signed type.");
42  }
43 
44  unsigned getWidth() const { return Width; }
45  unsigned getScale() const { return Scale; }
46  bool isSigned() const { return IsSigned; }
47  bool isSaturated() const { return IsSaturated; }
48  bool hasUnsignedPadding() const { return HasUnsignedPadding; }
49 
50  void setSaturated(bool Saturated) { IsSaturated = Saturated; }
51 
52  /// Return the number of integral bits represented by these semantics. These
53  /// are separate from the fractional bits and do not include the sign or
54  /// padding bit.
55  unsigned getIntegralBits() const {
56  if (IsSigned || (!IsSigned && HasUnsignedPadding))
57  return Width - Scale - 1;
58  else
59  return Width - Scale;
60  }
61 
62  /// Return the FixedPointSemantics that allows for calculating the full
63  /// precision semantic that can precisely represent the precision and ranges
64  /// of both input values. This does not compute the resulting semantics for a
65  /// given binary operation.
67  getCommonSemantics(const FixedPointSemantics &Other) const;
68 
69  /// Return the FixedPointSemantics for an integer type.
71  bool IsSigned) {
72  return FixedPointSemantics(Width, /*Scale=*/0, IsSigned,
73  /*IsSaturated=*/false,
74  /*HasUnsignedPadding=*/false);
75  }
76 
77 private:
78  unsigned Width;
79  unsigned Scale;
80  bool IsSigned;
81  bool IsSaturated;
82  bool HasUnsignedPadding;
83 };
84 
85 /// The APFixedPoint class works similarly to APInt/APSInt in that it is a
86 /// functional replacement for a scaled integer. It is meant to replicate the
87 /// fixed point types proposed in ISO/IEC JTC1 SC22 WG14 N1169. The class carries
88 /// info about the fixed point type's width, sign, scale, and saturation, and
89 /// provides different operations that would normally be performed on fixed point
90 /// types.
91 ///
92 /// Semantically this does not represent any existing C type other than fixed
93 /// point types and should eventually be moved to LLVM if fixed point types gain
94 /// native IR support.
95 class APFixedPoint {
96  public:
97  APFixedPoint(const llvm::APInt &Val, const FixedPointSemantics &Sema)
98  : Val(Val, !Sema.isSigned()), Sema(Sema) {
99  assert(Val.getBitWidth() == Sema.getWidth() &&
100  "The value should have a bit width that matches the Sema width");
101  }
102 
103  APFixedPoint(uint64_t Val, const FixedPointSemantics &Sema)
104  : APFixedPoint(llvm::APInt(Sema.getWidth(), Val, Sema.isSigned()),
105  Sema) {}
106 
107  // Zero initialization.
109 
110  llvm::APSInt getValue() const { return llvm::APSInt(Val, !Sema.isSigned()); }
111  inline unsigned getWidth() const { return Sema.getWidth(); }
112  inline unsigned getScale() const { return Sema.getScale(); }
113  inline bool isSaturated() const { return Sema.isSaturated(); }
114  inline bool isSigned() const { return Sema.isSigned(); }
115  inline bool hasPadding() const { return Sema.hasUnsignedPadding(); }
117 
118  bool getBoolValue() const { return Val.getBoolValue(); }
119 
120  // Convert this number to match the semantics provided. If the overflow
121  // parameter is provided, set this value to true or false to indicate if this
122  // operation results in an overflow.
123  APFixedPoint convert(const FixedPointSemantics &DstSema,
124  bool *Overflow = nullptr) const;
125 
126  // Perform binary operations on a fixed point type. The resulting fixed point
127  // value will be in the common, full precision semantics that can represent
128  // the precision and ranges os both input values. See convert() for an
129  // explanation of the Overflow parameter.
130  APFixedPoint add(const APFixedPoint &Other, bool *Overflow = nullptr) const;
131 
132  /// Perform a unary negation (-X) on this fixed point type, taking into
133  /// account saturation if applicable.
134  APFixedPoint negate(bool *Overflow = nullptr) const;
135 
136  APFixedPoint shr(unsigned Amt) const {
137  return APFixedPoint(Val >> Amt, Sema);
138  }
139 
140  APFixedPoint shl(unsigned Amt) const {
141  return APFixedPoint(Val << Amt, Sema);
142  }
143 
144  /// Return the integral part of this fixed point number, rounded towards
145  /// zero. (-2.5k -> -2)
146  llvm::APSInt getIntPart() const {
147  if (Val < 0 && Val != -Val) // Cover the case when we have the min val
148  return -(-Val >> getScale());
149  else
150  return Val >> getScale();
151  }
152 
153  /// Return the integral part of this fixed point number, rounded towards
154  /// zero. The value is stored into an APSInt with the provided width and sign.
155  /// If the overflow parameter is provided, and the integral value is not able
156  /// to be fully stored in the provided width and sign, the overflow parameter
157  /// is set to true.
158  ///
159  /// If the overflow parameter is provided, set this value to true or false to
160  /// indicate if this operation results in an overflow.
161  llvm::APSInt convertToInt(unsigned DstWidth, bool DstSign,
162  bool *Overflow = nullptr) const;
163 
164  void toString(llvm::SmallVectorImpl<char> &Str) const;
165  std::string toString() const {
167  toString(S);
168  return S.str();
169  }
170 
171  // If LHS > RHS, return 1. If LHS == RHS, return 0. If LHS < RHS, return -1.
172  int compare(const APFixedPoint &Other) const;
173  bool operator==(const APFixedPoint &Other) const {
174  return compare(Other) == 0;
175  }
176  bool operator!=(const APFixedPoint &Other) const {
177  return compare(Other) != 0;
178  }
179  bool operator>(const APFixedPoint &Other) const { return compare(Other) > 0; }
180  bool operator<(const APFixedPoint &Other) const { return compare(Other) < 0; }
181  bool operator>=(const APFixedPoint &Other) const {
182  return compare(Other) >= 0;
183  }
184  bool operator<=(const APFixedPoint &Other) const {
185  return compare(Other) <= 0;
186  }
187 
188  static APFixedPoint getMax(const FixedPointSemantics &Sema);
189  static APFixedPoint getMin(const FixedPointSemantics &Sema);
190 
191  /// Create an APFixedPoint with a value equal to that of the provided integer,
192  /// and in the same semantics as the provided target semantics. If the value
193  /// is not able to fit in the specified fixed point semantics, and the
194  /// overflow parameter is provided, it is set to true.
195  static APFixedPoint getFromIntValue(const llvm::APSInt &Value,
196  const FixedPointSemantics &DstFXSema,
197  bool *Overflow = nullptr);
198 
199 private:
200  llvm::APSInt Val;
201  FixedPointSemantics Sema;
202 };
203 
204 inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
205  const APFixedPoint &FX) {
206  OS << FX.toString();
207  return OS;
208 }
209 
210 } // namespace clang
211 
212 #endif
bool getBoolValue() const
Definition: FixedPoint.h:118
llvm::APSInt getValue() const
Definition: FixedPoint.h:110
DominatorTree GraphTraits specialization so the DominatorTree can be iterable by generic graph iterat...
Definition: Dominators.h:29
The fixed point semantics work similarly to llvm::fltSemantics.
Definition: FixedPoint.h:33
unsigned getScale() const
Definition: FixedPoint.h:112
const DiagnosticBuilder & operator<<(const DiagnosticBuilder &DB, const Attr *At)
Definition: Attr.h:335
unsigned getWidth() const
Definition: FixedPoint.h:111
bool isSaturated() const
Definition: FixedPoint.h:113
bool operator!=(const APFixedPoint &Other) const
Definition: FixedPoint.h:176
llvm::APSInt getIntPart() const
Return the integral part of this fixed point number, rounded towards zero.
Definition: FixedPoint.h:146
void setSaturated(bool Saturated)
Definition: FixedPoint.h:50
static std::string toString(const clang::SanitizerSet &Sanitizers)
Produce a string containing comma-separated names of sanitizers in Sanitizers set.
unsigned getIntegralBits() const
Return the number of integral bits represented by these semantics.
Definition: FixedPoint.h:55
bool operator>(const APFixedPoint &Other) const
Definition: FixedPoint.h:179
bool isSigned() const
Definition: FixedPoint.h:114
unsigned getScale() const
Definition: FixedPoint.h:45
std::string toString() const
Definition: FixedPoint.h:165
The APFixedPoint class works similarly to APInt/APSInt in that it is a functional replacement for a s...
Definition: FixedPoint.h:95
bool hasPadding() const
Definition: FixedPoint.h:115
Sema - This implements semantic analysis and AST building for C.
Definition: Sema.h:328
static bool compare(const PathDiagnostic &X, const PathDiagnostic &Y)
APFixedPoint(const FixedPointSemantics &Sema)
Definition: FixedPoint.h:108
APFixedPoint shl(unsigned Amt) const
Definition: FixedPoint.h:140
bool operator<(const APFixedPoint &Other) const
Definition: FixedPoint.h:180
APFixedPoint(uint64_t Val, const FixedPointSemantics &Sema)
Definition: FixedPoint.h:103
bool hasUnsignedPadding() const
Definition: FixedPoint.h:48
FixedPointSemantics getCommonSemantics(const FixedPointSemantics &Other) const
Return the FixedPointSemantics that allows for calculating the full precision semantic that can preci...
Definition: FixedPoint.cpp:127
bool operator<=(const APFixedPoint &Other) const
Definition: FixedPoint.h:184
void toString(llvm::SmallVectorImpl< char > &Str) const
Definition: FixedPoint.cpp:176
FixedPointSemantics getSemantics() const
Definition: FixedPoint.h:116
FixedPointSemantics(unsigned Width, unsigned Scale, bool IsSigned, bool IsSaturated, bool HasUnsignedPadding)
Definition: FixedPoint.h:35
bool operator==(const APFixedPoint &Other) const
Definition: FixedPoint.h:173
bool isSaturated() const
Definition: FixedPoint.h:47
Dataflow Directional Tag Classes.
APFixedPoint shr(unsigned Amt) const
Definition: FixedPoint.h:136
static FixedPointSemantics GetIntegerSemantics(unsigned Width, bool IsSigned)
Return the FixedPointSemantics for an integer type.
Definition: FixedPoint.h:70
unsigned getWidth() const
Definition: FixedPoint.h:44
APFixedPoint(const llvm::APInt &Val, const FixedPointSemantics &Sema)
Definition: FixedPoint.h:97
bool operator>=(const APFixedPoint &Other) const
Definition: FixedPoint.h:181