Bug Summary

File:lib/Target/AArch64/AArch64CompressJumpTables.cpp
Warning:line 121, column 42
Called C++ object pointer is null

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 AArch64CompressJumpTables.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 -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-9~svn359999/build-llvm/lib/Target/AArch64 -I /build/llvm-toolchain-snapshot-9~svn359999/lib/Target/AArch64 -I /build/llvm-toolchain-snapshot-9~svn359999/build-llvm/include -I /build/llvm-toolchain-snapshot-9~svn359999/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/include/clang/9.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-9/lib/clang/9.0.0/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++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-9~svn359999/build-llvm/lib/Target/AArch64 -fdebug-prefix-map=/build/llvm-toolchain-snapshot-9~svn359999=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2019-05-06-051613-19774-1 -x c++ /build/llvm-toolchain-snapshot-9~svn359999/lib/Target/AArch64/AArch64CompressJumpTables.cpp -faddrsig
1//==-- AArch64CompressJumpTables.cpp - Compress jump tables for AArch64 --====//
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// This pass looks at the basic blocks each jump-table refers to and works out
8// whether they can be emitted in a compressed form (with 8 or 16-bit
9// entries). If so, it changes the opcode and flags them in the associated
10// AArch64FunctionInfo.
11//
12//===----------------------------------------------------------------------===//
13
14#include "AArch64.h"
15#include "AArch64MachineFunctionInfo.h"
16#include "AArch64Subtarget.h"
17#include "llvm/ADT/Statistic.h"
18#include "llvm/CodeGen/MachineFunctionPass.h"
19#include "llvm/CodeGen/MachineJumpTableInfo.h"
20#include "llvm/CodeGen/TargetInstrInfo.h"
21#include "llvm/CodeGen/TargetSubtargetInfo.h"
22#include "llvm/MC/MCContext.h"
23#include "llvm/Support/Debug.h"
24
25using namespace llvm;
26
27#define DEBUG_TYPE"aarch64-jump-tables" "aarch64-jump-tables"
28
29STATISTIC(NumJT8, "Number of jump-tables with 1-byte entries")static llvm::Statistic NumJT8 = {"aarch64-jump-tables", "NumJT8"
, "Number of jump-tables with 1-byte entries", {0}, {false}};
30STATISTIC(NumJT16, "Number of jump-tables with 2-byte entries")static llvm::Statistic NumJT16 = {"aarch64-jump-tables", "NumJT16"
, "Number of jump-tables with 2-byte entries", {0}, {false}};
31STATISTIC(NumJT32, "Number of jump-tables with 4-byte entries")static llvm::Statistic NumJT32 = {"aarch64-jump-tables", "NumJT32"
, "Number of jump-tables with 4-byte entries", {0}, {false}};
32
33namespace {
34class AArch64CompressJumpTables : public MachineFunctionPass {
35 const TargetInstrInfo *TII;
36 MachineFunction *MF;
37 SmallVector<int, 8> BlockInfo;
38
39 int computeBlockSize(MachineBasicBlock &MBB);
40 void scanFunction();
41
42 bool compressJumpTable(MachineInstr &MI, int Offset);
43
44public:
45 static char ID;
46 AArch64CompressJumpTables() : MachineFunctionPass(ID) {
47 initializeAArch64CompressJumpTablesPass(*PassRegistry::getPassRegistry());
48 }
49
50 bool runOnMachineFunction(MachineFunction &MF) override;
51
52 MachineFunctionProperties getRequiredProperties() const override {
53 return MachineFunctionProperties().set(
54 MachineFunctionProperties::Property::NoVRegs);
55 }
56 StringRef getPassName() const override {
57 return "AArch64 Compress Jump Tables";
58 }
59};
60char AArch64CompressJumpTables::ID = 0;
61}
62
63INITIALIZE_PASS(AArch64CompressJumpTables, DEBUG_TYPE,static void *initializeAArch64CompressJumpTablesPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "AArch64 compress jump tables pass"
, "aarch64-jump-tables", &AArch64CompressJumpTables::ID, PassInfo
::NormalCtor_t(callDefaultCtor<AArch64CompressJumpTables>
), false, false); Registry.registerPass(*PI, true); return PI
; } static llvm::once_flag InitializeAArch64CompressJumpTablesPassFlag
; void llvm::initializeAArch64CompressJumpTablesPass(PassRegistry
&Registry) { llvm::call_once(InitializeAArch64CompressJumpTablesPassFlag
, initializeAArch64CompressJumpTablesPassOnce, std::ref(Registry
)); }
64 "AArch64 compress jump tables pass", false, false)static void *initializeAArch64CompressJumpTablesPassOnce(PassRegistry
&Registry) { PassInfo *PI = new PassInfo( "AArch64 compress jump tables pass"
, "aarch64-jump-tables", &AArch64CompressJumpTables::ID, PassInfo
::NormalCtor_t(callDefaultCtor<AArch64CompressJumpTables>
), false, false); Registry.registerPass(*PI, true); return PI
; } static llvm::once_flag InitializeAArch64CompressJumpTablesPassFlag
; void llvm::initializeAArch64CompressJumpTablesPass(PassRegistry
&Registry) { llvm::call_once(InitializeAArch64CompressJumpTablesPassFlag
, initializeAArch64CompressJumpTablesPassOnce, std::ref(Registry
)); }
65
66int AArch64CompressJumpTables::computeBlockSize(MachineBasicBlock &MBB) {
67 int Size = 0;
68 for (const MachineInstr &MI : MBB)
69 Size += TII->getInstSizeInBytes(MI);
70 return Size;
71}
72
73void AArch64CompressJumpTables::scanFunction() {
74 BlockInfo.clear();
75 BlockInfo.resize(MF->getNumBlockIDs());
76
77 int Offset = 0;
78 for (MachineBasicBlock &MBB : *MF) {
79 BlockInfo[MBB.getNumber()] = Offset;
80 Offset += computeBlockSize(MBB);
81 }
82}
83
84bool AArch64CompressJumpTables::compressJumpTable(MachineInstr &MI,
85 int Offset) {
86 if (MI.getOpcode() != AArch64::JumpTableDest32)
3
←
Assuming the condition is false
→
4
←
Taking false branch
→
87 return false;
88
89 int JTIdx = MI.getOperand(4).getIndex();
90 auto &JTInfo = *MF->getJumpTableInfo();
91 const MachineJumpTableEntry &JT = JTInfo.getJumpTables()[JTIdx];
92
93 // The jump-table might have been optimized away.
94 if (JT.MBBs.empty())
5
←
Assuming the condition is false
→
6
←
Taking false branch
→
95 return false;
96
97 int MaxOffset = std::numeric_limits<int>::min(),
98 MinOffset = std::numeric_limits<int>::max();
99 MachineBasicBlock *MinBlock = nullptr;
7
←
'MinBlock' initialized to a null pointer value
→
100 for (auto Block : JT.MBBs) {
101 int BlockOffset = BlockInfo[Block->getNumber()];
102 assert(BlockOffset % 4 == 0 && "misaligned basic block")((BlockOffset % 4 == 0 && "misaligned basic block") ?
static_cast<void> (0) : __assert_fail ("BlockOffset % 4 == 0 && \"misaligned basic block\""
, "/build/llvm-toolchain-snapshot-9~svn359999/lib/Target/AArch64/AArch64CompressJumpTables.cpp"
, 102, __PRETTY_FUNCTION__));
103
104 MaxOffset = std::max(MaxOffset, BlockOffset);
105 if (BlockOffset <= MinOffset) {
106 MinOffset = BlockOffset;
107 MinBlock = Block;
108 }
109 }
110
111 // The ADR instruction needed to calculate the address of the first reachable
112 // basic block can address +/-1MB.
113 if (!isInt<21>(MinOffset - Offset)) {
8
←
Taking false branch
→
114 ++NumJT32;
115 return false;
116 }
117
118 int Span = MaxOffset - MinOffset;
119 auto AFI = MF->getInfo<AArch64FunctionInfo>();
120 if (isUInt<8>(Span / 4)) {
9
←
Taking true branch
→
121 AFI->setJumpTableEntryInfo(JTIdx, 1, MinBlock->getSymbol());
10
←
Called C++ object pointer is null
122 MI.setDesc(TII->get(AArch64::JumpTableDest8));
123 ++NumJT8;
124 return true;
125 } else if (isUInt<16>(Span / 4)) {
126 AFI->setJumpTableEntryInfo(JTIdx, 2, MinBlock->getSymbol());
127 MI.setDesc(TII->get(AArch64::JumpTableDest16));
128 ++NumJT16;
129 return true;
130 }
131
132 ++NumJT32;
133 return false;
134}
135
136bool AArch64CompressJumpTables::runOnMachineFunction(MachineFunction &MFIn) {
137 bool Changed = false;
138 MF = &MFIn;
139
140 const auto &ST = MF->getSubtarget<AArch64Subtarget>();
141 TII = ST.getInstrInfo();
142
143 if (ST.force32BitJumpTables() && !MF->getFunction().hasMinSize())
1
Assuming the condition is false
→
144 return false;
145
146 scanFunction();
147
148 for (MachineBasicBlock &MBB : *MF) {
149 int Offset = BlockInfo[MBB.getNumber()];
150 for (MachineInstr &MI : MBB) {
151 Changed |= compressJumpTable(MI, Offset);
2
←
Calling 'AArch64CompressJumpTables::compressJumpTable'
→
152 Offset += TII->getInstSizeInBytes(MI);
153 }
154 }
155
156 return Changed;
157}
158
159FunctionPass *llvm::createAArch64CompressJumpTablesPass() {
160 return new AArch64CompressJumpTables();
161}