Bug Summary

File:llvm/lib/Target/Mips/MipsAnalyzeImmediate.cpp
Warning:line 47, column 20
The result of the right shift is undefined due to shifting by '64', which is greater or equal to the width of type 'uint64_t'

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name MipsAnalyzeImmediate.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=none -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-10/lib/clang/10.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/build-llvm/lib/Target/Mips -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/Target/Mips -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/build-llvm/include -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-10/lib/clang/10.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/build-llvm/lib/Target/Mips -fdebug-prefix-map=/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-01-13-084841-49055-1 -x c++ /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/Target/Mips/MipsAnalyzeImmediate.cpp

/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/Target/Mips/MipsAnalyzeImmediate.cpp

1//===- MipsAnalyzeImmediate.cpp - Analyze Immediates ----------------------===//
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#include "MipsAnalyzeImmediate.h"
10#include "Mips.h"
11#include "llvm/Support/MathExtras.h"
12#include <cassert>
13#include <cstdint>
14#include <iterator>
15
16using namespace llvm;
17
18MipsAnalyzeImmediate::Inst::Inst(unsigned O, unsigned I) : Opc(O), ImmOpnd(I) {}
19
20// Add I to the instruction sequences.
21void MipsAnalyzeImmediate::AddInstr(InstSeqLs &SeqLs, const Inst &I) {
22 // Add an instruction seqeunce consisting of just I.
23 if (SeqLs.empty()) {
24 SeqLs.push_back(InstSeq(1, I));
25 return;
26 }
27
28 for (InstSeqLs::iterator Iter = SeqLs.begin(); Iter != SeqLs.end(); ++Iter)
29 Iter->push_back(I);
30}
31
32void MipsAnalyzeImmediate::GetInstSeqLsADDiu(uint64_t Imm, unsigned RemSize,
33 InstSeqLs &SeqLs) {
34 GetInstSeqLs((Imm + 0x8000ULL) & 0xffffffffffff0000ULL, RemSize, SeqLs);
7
Calling 'MipsAnalyzeImmediate::GetInstSeqLs'
35 AddInstr(SeqLs, Inst(ADDiu, Imm & 0xffffULL));
36}
37
38void MipsAnalyzeImmediate::GetInstSeqLsORi(uint64_t Imm, unsigned RemSize,
39 InstSeqLs &SeqLs) {
40 GetInstSeqLs(Imm & 0xffffffffffff0000ULL, RemSize, SeqLs);
41 AddInstr(SeqLs, Inst(ORi, Imm & 0xffffULL));
42}
43
44void MipsAnalyzeImmediate::GetInstSeqLsSLL(uint64_t Imm, unsigned RemSize,
45 InstSeqLs &SeqLs) {
46 unsigned Shamt = countTrailingZeros(Imm);
14
Calling 'countTrailingZeros<unsigned long>'
21
Returning from 'countTrailingZeros<unsigned long>'
22
'Shamt' initialized to 64
47 GetInstSeqLs(Imm >> Shamt, RemSize - Shamt, SeqLs);
23
The result of the right shift is undefined due to shifting by '64', which is greater or equal to the width of type 'uint64_t'
48 AddInstr(SeqLs, Inst(SLL, Shamt));
49}
50
51void MipsAnalyzeImmediate::GetInstSeqLs(uint64_t Imm, unsigned RemSize,
52 InstSeqLs &SeqLs) {
53 uint64_t MaskedImm = Imm & (0xffffffffffffffffULL >> (64 - Size));
54
55 // Do nothing if Imm is 0.
56 if (!MaskedImm)
8
Assuming 'MaskedImm' is not equal to 0
9
Taking false branch
57 return;
58
59 // A single ADDiu will do if RemSize <= 16.
60 if (RemSize
9.1
'RemSize' is > 16
9.1
'RemSize' is > 16
<= 16) {
10
Taking false branch
61 AddInstr(SeqLs, Inst(ADDiu, MaskedImm));
62 return;
63 }
64
65 // Shift if the lower 16-bit is cleared.
66 if (!(Imm & 0xffff)) {
11
Assuming the condition is true
12
Taking true branch
67 GetInstSeqLsSLL(Imm, RemSize, SeqLs);
13
Calling 'MipsAnalyzeImmediate::GetInstSeqLsSLL'
68 return;
69 }
70
71 GetInstSeqLsADDiu(Imm, RemSize, SeqLs);
72
73 // If bit 15 is cleared, it doesn't make a difference whether the last
74 // instruction is an ADDiu or ORi. In that case, do not call GetInstSeqLsORi.
75 if (Imm & 0x8000) {
76 InstSeqLs SeqLsORi;
77 GetInstSeqLsORi(Imm, RemSize, SeqLsORi);
78 SeqLs.append(std::make_move_iterator(SeqLsORi.begin()),
79 std::make_move_iterator(SeqLsORi.end()));
80 }
81}
82
83// Replace a ADDiu & SLL pair with a LUi.
84// e.g. the following two instructions
85// ADDiu 0x0111
86// SLL 18
87// are replaced with
88// LUi 0x444
89void MipsAnalyzeImmediate::ReplaceADDiuSLLWithLUi(InstSeq &Seq) {
90 // Check if the first two instructions are ADDiu and SLL and the shift amount
91 // is at least 16.
92 if ((Seq.size() < 2) || (Seq[0].Opc != ADDiu) ||
93 (Seq[1].Opc != SLL) || (Seq[1].ImmOpnd < 16))
94 return;
95
96 // Sign-extend and shift operand of ADDiu and see if it still fits in 16-bit.
97 int64_t Imm = SignExtend64<16>(Seq[0].ImmOpnd);
98 int64_t ShiftedImm = (uint64_t)Imm << (Seq[1].ImmOpnd - 16);
99
100 if (!isInt<16>(ShiftedImm))
101 return;
102
103 // Replace the first instruction and erase the second.
104 Seq[0].Opc = LUi;
105 Seq[0].ImmOpnd = (unsigned)(ShiftedImm & 0xffff);
106 Seq.erase(Seq.begin() + 1);
107}
108
109void MipsAnalyzeImmediate::GetShortestSeq(InstSeqLs &SeqLs, InstSeq &Insts) {
110 InstSeqLs::iterator ShortestSeq = SeqLs.end();
111 // The length of an instruction sequence is at most 7.
112 unsigned ShortestLength = 8;
113
114 for (InstSeqLs::iterator S = SeqLs.begin(); S != SeqLs.end(); ++S) {
115 ReplaceADDiuSLLWithLUi(*S);
116 assert(S->size() <= 7)((S->size() <= 7) ? static_cast<void> (0) : __assert_fail
("S->size() <= 7", "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/Target/Mips/MipsAnalyzeImmediate.cpp"
, 116, __PRETTY_FUNCTION__))
;
117
118 if (S->size() < ShortestLength) {
119 ShortestSeq = S;
120 ShortestLength = S->size();
121 }
122 }
123
124 Insts.clear();
125 Insts.append(ShortestSeq->begin(), ShortestSeq->end());
126}
127
128const MipsAnalyzeImmediate::InstSeq
129&MipsAnalyzeImmediate::Analyze(uint64_t Imm, unsigned Size,
130 bool LastInstrIsADDiu) {
131 this->Size = Size;
132
133 if (Size == 32) {
1
Assuming 'Size' is equal to 32
2
Taking true branch
134 ADDiu = Mips::ADDiu;
135 ORi = Mips::ORi;
136 SLL = Mips::SLL;
137 LUi = Mips::LUi;
138 } else {
139 ADDiu = Mips::DADDiu;
140 ORi = Mips::ORi64;
141 SLL = Mips::DSLL;
142 LUi = Mips::LUi64;
143 }
144
145 InstSeqLs SeqLs;
146
147 // Get the list of instruction sequences.
148 if (LastInstrIsADDiu | !Imm)
3
Assuming 'Imm' is not equal to 0
4
Assuming the condition is true
5
Taking true branch
149 GetInstSeqLsADDiu(Imm, Size, SeqLs);
6
Calling 'MipsAnalyzeImmediate::GetInstSeqLsADDiu'
150 else
151 GetInstSeqLs(Imm, Size, SeqLs);
152
153 // Set Insts to the shortest instruction sequence.
154 GetShortestSeq(SeqLs, Insts);
155
156 return Insts;
157}

/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h

1//===-- llvm/Support/MathExtras.h - Useful math functions -------*- 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// This file contains some functions that are useful for math stuff.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_SUPPORT_MATHEXTRAS_H
14#define LLVM_SUPPORT_MATHEXTRAS_H
15
16#include "llvm/Support/Compiler.h"
17#include "llvm/Support/SwapByteOrder.h"
18#include <algorithm>
19#include <cassert>
20#include <climits>
21#include <cstring>
22#include <limits>
23#include <type_traits>
24
25#ifdef __ANDROID_NDK__
26#include <android/api-level.h>
27#endif
28
29#ifdef _MSC_VER
30// Declare these intrinsics manually rather including intrin.h. It's very
31// expensive, and MathExtras.h is popular.
32// #include <intrin.h>
33extern "C" {
34unsigned char _BitScanForward(unsigned long *_Index, unsigned long _Mask);
35unsigned char _BitScanForward64(unsigned long *_Index, unsigned __int64 _Mask);
36unsigned char _BitScanReverse(unsigned long *_Index, unsigned long _Mask);
37unsigned char _BitScanReverse64(unsigned long *_Index, unsigned __int64 _Mask);
38}
39#endif
40
41namespace llvm {
42
43/// The behavior an operation has on an input of 0.
44enum ZeroBehavior {
45 /// The returned value is undefined.
46 ZB_Undefined,
47 /// The returned value is numeric_limits<T>::max()
48 ZB_Max,
49 /// The returned value is numeric_limits<T>::digits
50 ZB_Width
51};
52
53/// Mathematical constants.
54namespace numbers {
55// TODO: Track C++20 std::numbers.
56// TODO: Favor using the hexadecimal FP constants (requires C++17).
57constexpr double e = 2.7182818284590452354, // (0x1.5bf0a8b145749P+1) https://oeis.org/A001113
58 egamma = .57721566490153286061, // (0x1.2788cfc6fb619P-1) https://oeis.org/A001620
59 ln2 = .69314718055994530942, // (0x1.62e42fefa39efP-1) https://oeis.org/A002162
60 ln10 = 2.3025850929940456840, // (0x1.24bb1bbb55516P+1) https://oeis.org/A002392
61 log2e = 1.4426950408889634074, // (0x1.71547652b82feP+0)
62 log10e = .43429448190325182765, // (0x1.bcb7b1526e50eP-2)
63 pi = 3.1415926535897932385, // (0x1.921fb54442d18P+1) https://oeis.org/A000796
64 inv_pi = .31830988618379067154, // (0x1.45f306bc9c883P-2) https://oeis.org/A049541
65 sqrtpi = 1.7724538509055160273, // (0x1.c5bf891b4ef6bP+0) https://oeis.org/A002161
66 inv_sqrtpi = .56418958354775628695, // (0x1.20dd750429b6dP-1) https://oeis.org/A087197
67 sqrt2 = 1.4142135623730950488, // (0x1.6a09e667f3bcdP+0) https://oeis.org/A00219
68 inv_sqrt2 = .70710678118654752440, // (0x1.6a09e667f3bcdP-1)
69 sqrt3 = 1.7320508075688772935, // (0x1.bb67ae8584caaP+0) https://oeis.org/A002194
70 inv_sqrt3 = .57735026918962576451, // (0x1.279a74590331cP-1)
71 phi = 1.6180339887498948482; // (0x1.9e3779b97f4a8P+0) https://oeis.org/A001622
72constexpr float ef = 2.71828183F, // (0x1.5bf0a8P+1) https://oeis.org/A001113
73 egammaf = .577215665F, // (0x1.2788d0P-1) https://oeis.org/A001620
74 ln2f = .693147181F, // (0x1.62e430P-1) https://oeis.org/A002162
75 ln10f = 2.30258509F, // (0x1.26bb1cP+1) https://oeis.org/A002392
76 log2ef = 1.44269504F, // (0x1.715476P+0)
77 log10ef = .434294482F, // (0x1.bcb7b2P-2)
78 pif = 3.14159265F, // (0x1.921fb6P+1) https://oeis.org/A000796
79 inv_pif = .318309886F, // (0x1.45f306P-2) https://oeis.org/A049541
80 sqrtpif = 1.77245385F, // (0x1.c5bf8aP+0) https://oeis.org/A002161
81 inv_sqrtpif = .564189584F, // (0x1.20dd76P-1) https://oeis.org/A087197
82 sqrt2f = 1.41421356F, // (0x1.6a09e6P+0) https://oeis.org/A002193
83 inv_sqrt2f = .707106781F, // (0x1.6a09e6P-1)
84 sqrt3f = 1.73205081F, // (0x1.bb67aeP+0) https://oeis.org/A002194
85 inv_sqrt3f = .577350269F, // (0x1.279a74P-1)
86 phif = 1.61803399F; // (0x1.9e377aP+0) https://oeis.org/A001622
87} // namespace numbers
88
89namespace detail {
90template <typename T, std::size_t SizeOfT> struct TrailingZerosCounter {
91 static unsigned count(T Val, ZeroBehavior) {
92 if (!Val)
93 return std::numeric_limits<T>::digits;
94 if (Val & 0x1)
95 return 0;
96
97 // Bisection method.
98 unsigned ZeroBits = 0;
99 T Shift = std::numeric_limits<T>::digits >> 1;
100 T Mask = std::numeric_limits<T>::max() >> Shift;
101 while (Shift) {
102 if ((Val & Mask) == 0) {
103 Val >>= Shift;
104 ZeroBits |= Shift;
105 }
106 Shift >>= 1;
107 Mask >>= Shift;
108 }
109 return ZeroBits;
110 }
111};
112
113#if defined(__GNUC__4) || defined(_MSC_VER)
114template <typename T> struct TrailingZerosCounter<T, 4> {
115 static unsigned count(T Val, ZeroBehavior ZB) {
116 if (ZB != ZB_Undefined && Val == 0)
117 return 32;
118
119#if __has_builtin(__builtin_ctz)1 || defined(__GNUC__4)
120 return __builtin_ctz(Val);
121#elif defined(_MSC_VER)
122 unsigned long Index;
123 _BitScanForward(&Index, Val);
124 return Index;
125#endif
126 }
127};
128
129#if !defined(_MSC_VER) || defined(_M_X64)
130template <typename T> struct TrailingZerosCounter<T, 8> {
131 static unsigned count(T Val, ZeroBehavior ZB) {
132 if (ZB
15.1
'ZB' is not equal to ZB_Undefined
15.1
'ZB' is not equal to ZB_Undefined
!= ZB_Undefined && Val == 0)
16
Assuming 'Val' is equal to 0
17
Taking true branch
133 return 64;
18
Returning the value 64
134
135#if __has_builtin(__builtin_ctzll)1 || defined(__GNUC__4)
136 return __builtin_ctzll(Val);
137#elif defined(_MSC_VER)
138 unsigned long Index;
139 _BitScanForward64(&Index, Val);
140 return Index;
141#endif
142 }
143};
144#endif
145#endif
146} // namespace detail
147
148/// Count number of 0's from the least significant bit to the most
149/// stopping at the first 1.
150///
151/// Only unsigned integral types are allowed.
152///
153/// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
154/// valid arguments.
155template <typename T>
156unsigned countTrailingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
157 static_assert(std::numeric_limits<T>::is_integer &&
158 !std::numeric_limits<T>::is_signed,
159 "Only unsigned integral types are allowed.");
160 return llvm::detail::TrailingZerosCounter<T, sizeof(T)>::count(Val, ZB);
15
Calling 'TrailingZerosCounter::count'
19
Returning from 'TrailingZerosCounter::count'
20
Returning the value 64
161}
162
163namespace detail {
164template <typename T, std::size_t SizeOfT> struct LeadingZerosCounter {
165 static unsigned count(T Val, ZeroBehavior) {
166 if (!Val)
167 return std::numeric_limits<T>::digits;
168
169 // Bisection method.
170 unsigned ZeroBits = 0;
171 for (T Shift = std::numeric_limits<T>::digits >> 1; Shift; Shift >>= 1) {
172 T Tmp = Val >> Shift;
173 if (Tmp)
174 Val = Tmp;
175 else
176 ZeroBits |= Shift;
177 }
178 return ZeroBits;
179 }
180};
181
182#if defined(__GNUC__4) || defined(_MSC_VER)
183template <typename T> struct LeadingZerosCounter<T, 4> {
184 static unsigned count(T Val, ZeroBehavior ZB) {
185 if (ZB != ZB_Undefined && Val == 0)
186 return 32;
187
188#if __has_builtin(__builtin_clz)1 || defined(__GNUC__4)
189 return __builtin_clz(Val);
190#elif defined(_MSC_VER)
191 unsigned long Index;
192 _BitScanReverse(&Index, Val);
193 return Index ^ 31;
194#endif
195 }
196};
197
198#if !defined(_MSC_VER) || defined(_M_X64)
199template <typename T> struct LeadingZerosCounter<T, 8> {
200 static unsigned count(T Val, ZeroBehavior ZB) {
201 if (ZB != ZB_Undefined && Val == 0)
202 return 64;
203
204#if __has_builtin(__builtin_clzll)1 || defined(__GNUC__4)
205 return __builtin_clzll(Val);
206#elif defined(_MSC_VER)
207 unsigned long Index;
208 _BitScanReverse64(&Index, Val);
209 return Index ^ 63;
210#endif
211 }
212};
213#endif
214#endif
215} // namespace detail
216
217/// Count number of 0's from the most significant bit to the least
218/// stopping at the first 1.
219///
220/// Only unsigned integral types are allowed.
221///
222/// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
223/// valid arguments.
224template <typename T>
225unsigned countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
226 static_assert(std::numeric_limits<T>::is_integer &&
227 !std::numeric_limits<T>::is_signed,
228 "Only unsigned integral types are allowed.");
229 return llvm::detail::LeadingZerosCounter<T, sizeof(T)>::count(Val, ZB);
230}
231
232/// Get the index of the first set bit starting from the least
233/// significant bit.
234///
235/// Only unsigned integral types are allowed.
236///
237/// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are
238/// valid arguments.
239template <typename T> T findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) {
240 if (ZB == ZB_Max && Val == 0)
241 return std::numeric_limits<T>::max();
242
243 return countTrailingZeros(Val, ZB_Undefined);
244}
245
246/// Create a bitmask with the N right-most bits set to 1, and all other
247/// bits set to 0. Only unsigned types are allowed.
248template <typename T> T maskTrailingOnes(unsigned N) {
249 static_assert(std::is_unsigned<T>::value, "Invalid type!");
250 const unsigned Bits = CHAR_BIT8 * sizeof(T);
251 assert(N <= Bits && "Invalid bit index")((N <= Bits && "Invalid bit index") ? static_cast<
void> (0) : __assert_fail ("N <= Bits && \"Invalid bit index\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 251, __PRETTY_FUNCTION__))
;
252 return N == 0 ? 0 : (T(-1) >> (Bits - N));
253}
254
255/// Create a bitmask with the N left-most bits set to 1, and all other
256/// bits set to 0. Only unsigned types are allowed.
257template <typename T> T maskLeadingOnes(unsigned N) {
258 return ~maskTrailingOnes<T>(CHAR_BIT8 * sizeof(T) - N);
259}
260
261/// Create a bitmask with the N right-most bits set to 0, and all other
262/// bits set to 1. Only unsigned types are allowed.
263template <typename T> T maskTrailingZeros(unsigned N) {
264 return maskLeadingOnes<T>(CHAR_BIT8 * sizeof(T) - N);
265}
266
267/// Create a bitmask with the N left-most bits set to 0, and all other
268/// bits set to 1. Only unsigned types are allowed.
269template <typename T> T maskLeadingZeros(unsigned N) {
270 return maskTrailingOnes<T>(CHAR_BIT8 * sizeof(T) - N);
271}
272
273/// Get the index of the last set bit starting from the least
274/// significant bit.
275///
276/// Only unsigned integral types are allowed.
277///
278/// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are
279/// valid arguments.
280template <typename T> T findLastSet(T Val, ZeroBehavior ZB = ZB_Max) {
281 if (ZB == ZB_Max && Val == 0)
282 return std::numeric_limits<T>::max();
283
284 // Use ^ instead of - because both gcc and llvm can remove the associated ^
285 // in the __builtin_clz intrinsic on x86.
286 return countLeadingZeros(Val, ZB_Undefined) ^
287 (std::numeric_limits<T>::digits - 1);
288}
289
290/// Macro compressed bit reversal table for 256 bits.
291///
292/// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
293static const unsigned char BitReverseTable256[256] = {
294#define R2(n) n, n + 2 * 64, n + 1 * 64, n + 3 * 64
295#define R4(n) R2(n), R2(n + 2 * 16), R2(n + 1 * 16), R2(n + 3 * 16)
296#define R6(n) R4(n), R4(n + 2 * 4), R4(n + 1 * 4), R4(n + 3 * 4)
297 R6(0), R6(2), R6(1), R6(3)
298#undef R2
299#undef R4
300#undef R6
301};
302
303/// Reverse the bits in \p Val.
304template <typename T>
305T reverseBits(T Val) {
306 unsigned char in[sizeof(Val)];
307 unsigned char out[sizeof(Val)];
308 std::memcpy(in, &Val, sizeof(Val));
309 for (unsigned i = 0; i < sizeof(Val); ++i)
310 out[(sizeof(Val) - i) - 1] = BitReverseTable256[in[i]];
311 std::memcpy(&Val, out, sizeof(Val));
312 return Val;
313}
314
315// NOTE: The following support functions use the _32/_64 extensions instead of
316// type overloading so that signed and unsigned integers can be used without
317// ambiguity.
318
319/// Return the high 32 bits of a 64 bit value.
320constexpr inline uint32_t Hi_32(uint64_t Value) {
321 return static_cast<uint32_t>(Value >> 32);
322}
323
324/// Return the low 32 bits of a 64 bit value.
325constexpr inline uint32_t Lo_32(uint64_t Value) {
326 return static_cast<uint32_t>(Value);
327}
328
329/// Make a 64-bit integer from a high / low pair of 32-bit integers.
330constexpr inline uint64_t Make_64(uint32_t High, uint32_t Low) {
331 return ((uint64_t)High << 32) | (uint64_t)Low;
332}
333
334/// Checks if an integer fits into the given bit width.
335template <unsigned N> constexpr inline bool isInt(int64_t x) {
336 return N >= 64 || (-(INT64_C(1)1L<<(N-1)) <= x && x < (INT64_C(1)1L<<(N-1)));
337}
338// Template specializations to get better code for common cases.
339template <> constexpr inline bool isInt<8>(int64_t x) {
340 return static_cast<int8_t>(x) == x;
341}
342template <> constexpr inline bool isInt<16>(int64_t x) {
343 return static_cast<int16_t>(x) == x;
344}
345template <> constexpr inline bool isInt<32>(int64_t x) {
346 return static_cast<int32_t>(x) == x;
347}
348
349/// Checks if a signed integer is an N bit number shifted left by S.
350template <unsigned N, unsigned S>
351constexpr inline bool isShiftedInt(int64_t x) {
352 static_assert(
353 N > 0, "isShiftedInt<0> doesn't make sense (refers to a 0-bit number.");
354 static_assert(N + S <= 64, "isShiftedInt<N, S> with N + S > 64 is too wide.");
355 return isInt<N + S>(x) && (x % (UINT64_C(1)1UL << S) == 0);
356}
357
358/// Checks if an unsigned integer fits into the given bit width.
359///
360/// This is written as two functions rather than as simply
361///
362/// return N >= 64 || X < (UINT64_C(1) << N);
363///
364/// to keep MSVC from (incorrectly) warning on isUInt<64> that we're shifting
365/// left too many places.
366template <unsigned N>
367constexpr inline typename std::enable_if<(N < 64), bool>::type
368isUInt(uint64_t X) {
369 static_assert(N > 0, "isUInt<0> doesn't make sense");
370 return X < (UINT64_C(1)1UL << (N));
371}
372template <unsigned N>
373constexpr inline typename std::enable_if<N >= 64, bool>::type
374isUInt(uint64_t X) {
375 return true;
376}
377
378// Template specializations to get better code for common cases.
379template <> constexpr inline bool isUInt<8>(uint64_t x) {
380 return static_cast<uint8_t>(x) == x;
381}
382template <> constexpr inline bool isUInt<16>(uint64_t x) {
383 return static_cast<uint16_t>(x) == x;
384}
385template <> constexpr inline bool isUInt<32>(uint64_t x) {
386 return static_cast<uint32_t>(x) == x;
387}
388
389/// Checks if a unsigned integer is an N bit number shifted left by S.
390template <unsigned N, unsigned S>
391constexpr inline bool isShiftedUInt(uint64_t x) {
392 static_assert(
393 N > 0, "isShiftedUInt<0> doesn't make sense (refers to a 0-bit number)");
394 static_assert(N + S <= 64,
395 "isShiftedUInt<N, S> with N + S > 64 is too wide.");
396 // Per the two static_asserts above, S must be strictly less than 64. So
397 // 1 << S is not undefined behavior.
398 return isUInt<N + S>(x) && (x % (UINT64_C(1)1UL << S) == 0);
399}
400
401/// Gets the maximum value for a N-bit unsigned integer.
402inline uint64_t maxUIntN(uint64_t N) {
403 assert(N > 0 && N <= 64 && "integer width out of range")((N > 0 && N <= 64 && "integer width out of range"
) ? static_cast<void> (0) : __assert_fail ("N > 0 && N <= 64 && \"integer width out of range\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 403, __PRETTY_FUNCTION__))
;
404
405 // uint64_t(1) << 64 is undefined behavior, so we can't do
406 // (uint64_t(1) << N) - 1
407 // without checking first that N != 64. But this works and doesn't have a
408 // branch.
409 return UINT64_MAX(18446744073709551615UL) >> (64 - N);
410}
411
412/// Gets the minimum value for a N-bit signed integer.
413inline int64_t minIntN(int64_t N) {
414 assert(N > 0 && N <= 64 && "integer width out of range")((N > 0 && N <= 64 && "integer width out of range"
) ? static_cast<void> (0) : __assert_fail ("N > 0 && N <= 64 && \"integer width out of range\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 414, __PRETTY_FUNCTION__))
;
415
416 return -(UINT64_C(1)1UL<<(N-1));
417}
418
419/// Gets the maximum value for a N-bit signed integer.
420inline int64_t maxIntN(int64_t N) {
421 assert(N > 0 && N <= 64 && "integer width out of range")((N > 0 && N <= 64 && "integer width out of range"
) ? static_cast<void> (0) : __assert_fail ("N > 0 && N <= 64 && \"integer width out of range\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 421, __PRETTY_FUNCTION__))
;
422
423 // This relies on two's complement wraparound when N == 64, so we convert to
424 // int64_t only at the very end to avoid UB.
425 return (UINT64_C(1)1UL << (N - 1)) - 1;
426}
427
428/// Checks if an unsigned integer fits into the given (dynamic) bit width.
429inline bool isUIntN(unsigned N, uint64_t x) {
430 return N >= 64 || x <= maxUIntN(N);
431}
432
433/// Checks if an signed integer fits into the given (dynamic) bit width.
434inline bool isIntN(unsigned N, int64_t x) {
435 return N >= 64 || (minIntN(N) <= x && x <= maxIntN(N));
436}
437
438/// Return true if the argument is a non-empty sequence of ones starting at the
439/// least significant bit with the remainder zero (32 bit version).
440/// Ex. isMask_32(0x0000FFFFU) == true.
441constexpr inline bool isMask_32(uint32_t Value) {
442 return Value && ((Value + 1) & Value) == 0;
443}
444
445/// Return true if the argument is a non-empty sequence of ones starting at the
446/// least significant bit with the remainder zero (64 bit version).
447constexpr inline bool isMask_64(uint64_t Value) {
448 return Value && ((Value + 1) & Value) == 0;
449}
450
451/// Return true if the argument contains a non-empty sequence of ones with the
452/// remainder zero (32 bit version.) Ex. isShiftedMask_32(0x0000FF00U) == true.
453constexpr inline bool isShiftedMask_32(uint32_t Value) {
454 return Value && isMask_32((Value - 1) | Value);
455}
456
457/// Return true if the argument contains a non-empty sequence of ones with the
458/// remainder zero (64 bit version.)
459constexpr inline bool isShiftedMask_64(uint64_t Value) {
460 return Value && isMask_64((Value - 1) | Value);
461}
462
463/// Return true if the argument is a power of two > 0.
464/// Ex. isPowerOf2_32(0x00100000U) == true (32 bit edition.)
465constexpr inline bool isPowerOf2_32(uint32_t Value) {
466 return Value && !(Value & (Value - 1));
467}
468
469/// Return true if the argument is a power of two > 0 (64 bit edition.)
470constexpr inline bool isPowerOf2_64(uint64_t Value) {
471 return Value && !(Value & (Value - 1));
472}
473
474/// Return a byte-swapped representation of the 16-bit argument.
475inline uint16_t ByteSwap_16(uint16_t Value) {
476 return sys::SwapByteOrder_16(Value);
477}
478
479/// Return a byte-swapped representation of the 32-bit argument.
480inline uint32_t ByteSwap_32(uint32_t Value) {
481 return sys::SwapByteOrder_32(Value);
482}
483
484/// Return a byte-swapped representation of the 64-bit argument.
485inline uint64_t ByteSwap_64(uint64_t Value) {
486 return sys::SwapByteOrder_64(Value);
487}
488
489/// Count the number of ones from the most significant bit to the first
490/// zero bit.
491///
492/// Ex. countLeadingOnes(0xFF0FFF00) == 8.
493/// Only unsigned integral types are allowed.
494///
495/// \param ZB the behavior on an input of all ones. Only ZB_Width and
496/// ZB_Undefined are valid arguments.
497template <typename T>
498unsigned countLeadingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
499 static_assert(std::numeric_limits<T>::is_integer &&
500 !std::numeric_limits<T>::is_signed,
501 "Only unsigned integral types are allowed.");
502 return countLeadingZeros<T>(~Value, ZB);
503}
504
505/// Count the number of ones from the least significant bit to the first
506/// zero bit.
507///
508/// Ex. countTrailingOnes(0x00FF00FF) == 8.
509/// Only unsigned integral types are allowed.
510///
511/// \param ZB the behavior on an input of all ones. Only ZB_Width and
512/// ZB_Undefined are valid arguments.
513template <typename T>
514unsigned countTrailingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
515 static_assert(std::numeric_limits<T>::is_integer &&
516 !std::numeric_limits<T>::is_signed,
517 "Only unsigned integral types are allowed.");
518 return countTrailingZeros<T>(~Value, ZB);
519}
520
521namespace detail {
522template <typename T, std::size_t SizeOfT> struct PopulationCounter {
523 static unsigned count(T Value) {
524 // Generic version, forward to 32 bits.
525 static_assert(SizeOfT <= 4, "Not implemented!");
526#if defined(__GNUC__4)
527 return __builtin_popcount(Value);
528#else
529 uint32_t v = Value;
530 v = v - ((v >> 1) & 0x55555555);
531 v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
532 return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
533#endif
534 }
535};
536
537template <typename T> struct PopulationCounter<T, 8> {
538 static unsigned count(T Value) {
539#if defined(__GNUC__4)
540 return __builtin_popcountll(Value);
541#else
542 uint64_t v = Value;
543 v = v - ((v >> 1) & 0x5555555555555555ULL);
544 v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL);
545 v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
546 return unsigned((uint64_t)(v * 0x0101010101010101ULL) >> 56);
547#endif
548 }
549};
550} // namespace detail
551
552/// Count the number of set bits in a value.
553/// Ex. countPopulation(0xF000F000) = 8
554/// Returns 0 if the word is zero.
555template <typename T>
556inline unsigned countPopulation(T Value) {
557 static_assert(std::numeric_limits<T>::is_integer &&
558 !std::numeric_limits<T>::is_signed,
559 "Only unsigned integral types are allowed.");
560 return detail::PopulationCounter<T, sizeof(T)>::count(Value);
561}
562
563/// Compile time Log2.
564/// Valid only for positive powers of two.
565template <size_t kValue> constexpr inline size_t CTLog2() {
566 static_assert(kValue > 0 && llvm::isPowerOf2_64(kValue),
567 "Value is not a valid power of 2");
568 return 1 + CTLog2<kValue / 2>();
569}
570
571template <> constexpr inline size_t CTLog2<1>() { return 0; }
572
573/// Return the log base 2 of the specified value.
574inline double Log2(double Value) {
575#if defined(__ANDROID_API__) && __ANDROID_API__ < 18
576 return __builtin_log(Value) / __builtin_log(2.0);
577#else
578 return log2(Value);
579#endif
580}
581
582/// Return the floor log base 2 of the specified value, -1 if the value is zero.
583/// (32 bit edition.)
584/// Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1, Log2_32(6) == 2
585inline unsigned Log2_32(uint32_t Value) {
586 return 31 - countLeadingZeros(Value);
587}
588
589/// Return the floor log base 2 of the specified value, -1 if the value is zero.
590/// (64 bit edition.)
591inline unsigned Log2_64(uint64_t Value) {
592 return 63 - countLeadingZeros(Value);
593}
594
595/// Return the ceil log base 2 of the specified value, 32 if the value is zero.
596/// (32 bit edition).
597/// Ex. Log2_32_Ceil(32) == 5, Log2_32_Ceil(1) == 0, Log2_32_Ceil(6) == 3
598inline unsigned Log2_32_Ceil(uint32_t Value) {
599 return 32 - countLeadingZeros(Value - 1);
600}
601
602/// Return the ceil log base 2 of the specified value, 64 if the value is zero.
603/// (64 bit edition.)
604inline unsigned Log2_64_Ceil(uint64_t Value) {
605 return 64 - countLeadingZeros(Value - 1);
606}
607
608/// Return the greatest common divisor of the values using Euclid's algorithm.
609template <typename T>
610inline T greatestCommonDivisor(T A, T B) {
611 while (B) {
612 T Tmp = B;
613 B = A % B;
614 A = Tmp;
615 }
616 return A;
617}
618
619inline uint64_t GreatestCommonDivisor64(uint64_t A, uint64_t B) {
620 return greatestCommonDivisor<uint64_t>(A, B);
621}
622
623/// This function takes a 64-bit integer and returns the bit equivalent double.
624inline double BitsToDouble(uint64_t Bits) {
625 double D;
626 static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
627 memcpy(&D, &Bits, sizeof(Bits));
628 return D;
629}
630
631/// This function takes a 32-bit integer and returns the bit equivalent float.
632inline float BitsToFloat(uint32_t Bits) {
633 float F;
634 static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
635 memcpy(&F, &Bits, sizeof(Bits));
636 return F;
637}
638
639/// This function takes a double and returns the bit equivalent 64-bit integer.
640/// Note that copying doubles around changes the bits of NaNs on some hosts,
641/// notably x86, so this routine cannot be used if these bits are needed.
642inline uint64_t DoubleToBits(double Double) {
643 uint64_t Bits;
644 static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
645 memcpy(&Bits, &Double, sizeof(Double));
646 return Bits;
647}
648
649/// This function takes a float and returns the bit equivalent 32-bit integer.
650/// Note that copying floats around changes the bits of NaNs on some hosts,
651/// notably x86, so this routine cannot be used if these bits are needed.
652inline uint32_t FloatToBits(float Float) {
653 uint32_t Bits;
654 static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
655 memcpy(&Bits, &Float, sizeof(Float));
656 return Bits;
657}
658
659/// A and B are either alignments or offsets. Return the minimum alignment that
660/// may be assumed after adding the two together.
661constexpr inline uint64_t MinAlign(uint64_t A, uint64_t B) {
662 // The largest power of 2 that divides both A and B.
663 //
664 // Replace "-Value" by "1+~Value" in the following commented code to avoid
665 // MSVC warning C4146
666 // return (A | B) & -(A | B);
667 return (A | B) & (1 + ~(A | B));
668}
669
670/// Returns the next power of two (in 64-bits) that is strictly greater than A.
671/// Returns zero on overflow.
672inline uint64_t NextPowerOf2(uint64_t A) {
673 A |= (A >> 1);
674 A |= (A >> 2);
675 A |= (A >> 4);
676 A |= (A >> 8);
677 A |= (A >> 16);
678 A |= (A >> 32);
679 return A + 1;
680}
681
682/// Returns the power of two which is less than or equal to the given value.
683/// Essentially, it is a floor operation across the domain of powers of two.
684inline uint64_t PowerOf2Floor(uint64_t A) {
685 if (!A) return 0;
686 return 1ull << (63 - countLeadingZeros(A, ZB_Undefined));
687}
688
689/// Returns the power of two which is greater than or equal to the given value.
690/// Essentially, it is a ceil operation across the domain of powers of two.
691inline uint64_t PowerOf2Ceil(uint64_t A) {
692 if (!A)
693 return 0;
694 return NextPowerOf2(A - 1);
695}
696
697/// Returns the next integer (mod 2**64) that is greater than or equal to
698/// \p Value and is a multiple of \p Align. \p Align must be non-zero.
699///
700/// If non-zero \p Skew is specified, the return value will be a minimal
701/// integer that is greater than or equal to \p Value and equal to
702/// \p Align * N + \p Skew for some integer N. If \p Skew is larger than
703/// \p Align, its value is adjusted to '\p Skew mod \p Align'.
704///
705/// Examples:
706/// \code
707/// alignTo(5, 8) = 8
708/// alignTo(17, 8) = 24
709/// alignTo(~0LL, 8) = 0
710/// alignTo(321, 255) = 510
711///
712/// alignTo(5, 8, 7) = 7
713/// alignTo(17, 8, 1) = 17
714/// alignTo(~0LL, 8, 3) = 3
715/// alignTo(321, 255, 42) = 552
716/// \endcode
717inline uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew = 0) {
718 assert(Align != 0u && "Align can't be 0.")((Align != 0u && "Align can't be 0.") ? static_cast<
void> (0) : __assert_fail ("Align != 0u && \"Align can't be 0.\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 718, __PRETTY_FUNCTION__))
;
719 Skew %= Align;
720 return (Value + Align - 1 - Skew) / Align * Align + Skew;
721}
722
723/// Returns the next integer (mod 2**64) that is greater than or equal to
724/// \p Value and is a multiple of \c Align. \c Align must be non-zero.
725template <uint64_t Align> constexpr inline uint64_t alignTo(uint64_t Value) {
726 static_assert(Align != 0u, "Align must be non-zero");
727 return (Value + Align - 1) / Align * Align;
728}
729
730/// Returns the integer ceil(Numerator / Denominator).
731inline uint64_t divideCeil(uint64_t Numerator, uint64_t Denominator) {
732 return alignTo(Numerator, Denominator) / Denominator;
733}
734
735/// Returns the integer nearest(Numerator / Denominator).
736inline uint64_t divideNearest(uint64_t Numerator, uint64_t Denominator) {
737 return (Numerator + (Denominator / 2)) / Denominator;
738}
739
740/// Returns the largest uint64_t less than or equal to \p Value and is
741/// \p Skew mod \p Align. \p Align must be non-zero
742inline uint64_t alignDown(uint64_t Value, uint64_t Align, uint64_t Skew = 0) {
743 assert(Align != 0u && "Align can't be 0.")((Align != 0u && "Align can't be 0.") ? static_cast<
void> (0) : __assert_fail ("Align != 0u && \"Align can't be 0.\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 743, __PRETTY_FUNCTION__))
;
744 Skew %= Align;
745 return (Value - Skew) / Align * Align + Skew;
746}
747
748/// Sign-extend the number in the bottom B bits of X to a 32-bit integer.
749/// Requires 0 < B <= 32.
750template <unsigned B> constexpr inline int32_t SignExtend32(uint32_t X) {
751 static_assert(B > 0, "Bit width can't be 0.");
752 static_assert(B <= 32, "Bit width out of range.");
753 return int32_t(X << (32 - B)) >> (32 - B);
754}
755
756/// Sign-extend the number in the bottom B bits of X to a 32-bit integer.
757/// Requires 0 < B < 32.
758inline int32_t SignExtend32(uint32_t X, unsigned B) {
759 assert(B > 0 && "Bit width can't be 0.")((B > 0 && "Bit width can't be 0.") ? static_cast<
void> (0) : __assert_fail ("B > 0 && \"Bit width can't be 0.\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 759, __PRETTY_FUNCTION__))
;
760 assert(B <= 32 && "Bit width out of range.")((B <= 32 && "Bit width out of range.") ? static_cast
<void> (0) : __assert_fail ("B <= 32 && \"Bit width out of range.\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 760, __PRETTY_FUNCTION__))
;
761 return int32_t(X << (32 - B)) >> (32 - B);
762}
763
764/// Sign-extend the number in the bottom B bits of X to a 64-bit integer.
765/// Requires 0 < B < 64.
766template <unsigned B> constexpr inline int64_t SignExtend64(uint64_t x) {
767 static_assert(B > 0, "Bit width can't be 0.");
768 static_assert(B <= 64, "Bit width out of range.");
769 return int64_t(x << (64 - B)) >> (64 - B);
770}
771
772/// Sign-extend the number in the bottom B bits of X to a 64-bit integer.
773/// Requires 0 < B < 64.
774inline int64_t SignExtend64(uint64_t X, unsigned B) {
775 assert(B > 0 && "Bit width can't be 0.")((B > 0 && "Bit width can't be 0.") ? static_cast<
void> (0) : __assert_fail ("B > 0 && \"Bit width can't be 0.\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 775, __PRETTY_FUNCTION__))
;
776 assert(B <= 64 && "Bit width out of range.")((B <= 64 && "Bit width out of range.") ? static_cast
<void> (0) : __assert_fail ("B <= 64 && \"Bit width out of range.\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/include/llvm/Support/MathExtras.h"
, 776, __PRETTY_FUNCTION__))
;
777 return int64_t(X << (64 - B)) >> (64 - B);
778}
779
780/// Subtract two unsigned integers, X and Y, of type T and return the absolute
781/// value of the result.
782template <typename T>
783typename std::enable_if<std::is_unsigned<T>::value, T>::type
784AbsoluteDifference(T X, T Y) {
785 return std::max(X, Y) - std::min(X, Y);
786}
787
788/// Add two unsigned integers, X and Y, of type T. Clamp the result to the
789/// maximum representable value of T on overflow. ResultOverflowed indicates if
790/// the result is larger than the maximum representable value of type T.
791template <typename T>
792typename std::enable_if<std::is_unsigned<T>::value, T>::type
793SaturatingAdd(T X, T Y, bool *ResultOverflowed = nullptr) {
794 bool Dummy;
795 bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy;
796 // Hacker's Delight, p. 29
797 T Z = X + Y;
798 Overflowed = (Z < X || Z < Y);
799 if (Overflowed)
800 return std::numeric_limits<T>::max();
801 else
802 return Z;
803}
804
805/// Multiply two unsigned integers, X and Y, of type T. Clamp the result to the
806/// maximum representable value of T on overflow. ResultOverflowed indicates if
807/// the result is larger than the maximum representable value of type T.
808template <typename T>
809typename std::enable_if<std::is_unsigned<T>::value, T>::type
810SaturatingMultiply(T X, T Y, bool *ResultOverflowed = nullptr) {
811 bool Dummy;
812 bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy;
813
814 // Hacker's Delight, p. 30 has a different algorithm, but we don't use that
815 // because it fails for uint16_t (where multiplication can have undefined
816 // behavior due to promotion to int), and requires a division in addition
817 // to the multiplication.
818
819 Overflowed = false;
820
821 // Log2(Z) would be either Log2Z or Log2Z + 1.
822 // Special case: if X or Y is 0, Log2_64 gives -1, and Log2Z
823 // will necessarily be less than Log2Max as desired.
824 int Log2Z = Log2_64(X) + Log2_64(Y);
825 const T Max = std::numeric_limits<T>::max();
826 int Log2Max = Log2_64(Max);
827 if (Log2Z < Log2Max) {
828 return X * Y;
829 }
830 if (Log2Z > Log2Max) {
831 Overflowed = true;
832 return Max;
833 }
834
835 // We're going to use the top bit, and maybe overflow one
836 // bit past it. Multiply all but the bottom bit then add
837 // that on at the end.
838 T Z = (X >> 1) * Y;
839 if (Z & ~(Max >> 1)) {
840 Overflowed = true;
841 return Max;
842 }
843 Z <<= 1;
844 if (X & 1)
845 return SaturatingAdd(Z, Y, ResultOverflowed);
846
847 return Z;
848}
849
850/// Multiply two unsigned integers, X and Y, and add the unsigned integer, A to
851/// the product. Clamp the result to the maximum representable value of T on
852/// overflow. ResultOverflowed indicates if the result is larger than the
853/// maximum representable value of type T.
854template <typename T>
855typename std::enable_if<std::is_unsigned<T>::value, T>::type
856SaturatingMultiplyAdd(T X, T Y, T A, bool *ResultOverflowed = nullptr) {
857 bool Dummy;
858 bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy;
859
860 T Product = SaturatingMultiply(X, Y, &Overflowed);
861 if (Overflowed)
862 return Product;
863
864 return SaturatingAdd(A, Product, &Overflowed);
865}
866
867/// Use this rather than HUGE_VALF; the latter causes warnings on MSVC.
868extern const float huge_valf;
869
870
871/// Add two signed integers, computing the two's complement truncated result,
872/// returning true if overflow occured.
873template <typename T>
874typename std::enable_if<std::is_signed<T>::value, T>::type
875AddOverflow(T X, T Y, T &Result) {
876#if __has_builtin(__builtin_add_overflow)1
877 return __builtin_add_overflow(X, Y, &Result);
878#else
879 // Perform the unsigned addition.
880 using U = typename std::make_unsigned<T>::type;
881 const U UX = static_cast<U>(X);
882 const U UY = static_cast<U>(Y);
883 const U UResult = UX + UY;
884
885 // Convert to signed.
886 Result = static_cast<T>(UResult);
887
888 // Adding two positive numbers should result in a positive number.
889 if (X > 0 && Y > 0)
890 return Result <= 0;
891 // Adding two negatives should result in a negative number.
892 if (X < 0 && Y < 0)
893 return Result >= 0;
894 return false;
895#endif
896}
897
898/// Subtract two signed integers, computing the two's complement truncated
899/// result, returning true if an overflow ocurred.
900template <typename T>
901typename std::enable_if<std::is_signed<T>::value, T>::type
902SubOverflow(T X, T Y, T &Result) {
903#if __has_builtin(__builtin_sub_overflow)1
904 return __builtin_sub_overflow(X, Y, &Result);
905#else
906 // Perform the unsigned addition.
907 using U = typename std::make_unsigned<T>::type;
908 const U UX = static_cast<U>(X);
909 const U UY = static_cast<U>(Y);
910 const U UResult = UX - UY;
911
912 // Convert to signed.
913 Result = static_cast<T>(UResult);
914
915 // Subtracting a positive number from a negative results in a negative number.
916 if (X <= 0 && Y > 0)
917 return Result >= 0;
918 // Subtracting a negative number from a positive results in a positive number.
919 if (X >= 0 && Y < 0)
920 return Result <= 0;
921 return false;
922#endif
923}
924
925
926/// Multiply two signed integers, computing the two's complement truncated
927/// result, returning true if an overflow ocurred.
928template <typename T>
929typename std::enable_if<std::is_signed<T>::value, T>::type
930MulOverflow(T X, T Y, T &Result) {
931 // Perform the unsigned multiplication on absolute values.
932 using U = typename std::make_unsigned<T>::type;
933 const U UX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
934 const U UY = Y < 0 ? (0 - static_cast<U>(Y)) : static_cast<U>(Y);
935 const U UResult = UX * UY;
936
937 // Convert to signed.
938 const bool IsNegative = (X < 0) ^ (Y < 0);
939 Result = IsNegative ? (0 - UResult) : UResult;
940
941 // If any of the args was 0, result is 0 and no overflow occurs.
942 if (UX == 0 || UY == 0)
943 return false;
944
945 // UX and UY are in [1, 2^n], where n is the number of digits.
946 // Check how the max allowed absolute value (2^n for negative, 2^(n-1) for
947 // positive) divided by an argument compares to the other.
948 if (IsNegative)
949 return UX > (static_cast<U>(std::numeric_limits<T>::max()) + U(1)) / UY;
950 else
951 return UX > (static_cast<U>(std::numeric_limits<T>::max())) / UY;
952}
953
954} // End llvm namespace
955
956#endif