Bug Summary

File:llvm/lib/CodeGen/MachineLoopInfo.cpp
Warning:line 143, column 33
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name MachineLoopInfo.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 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/CodeGen -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/CodeGen -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/CodeGen -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/include -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/include -D NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/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-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/CodeGen -fdebug-prefix-map=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-09-04-040900-46481-1 -x c++ /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/CodeGen/MachineLoopInfo.cpp
1//===- MachineLoopInfo.cpp - Natural Loop Calculator ----------------------===//
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 defines the MachineLoopInfo class that is used to identify natural
10// loops and determine the loop depth of various nodes of the CFG. Note that
11// the loops identified may actually be several natural loops that share the
12// same header node... not just a single natural loop.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/CodeGen/MachineLoopInfo.h"
17#include "llvm/Analysis/LoopInfoImpl.h"
18#include "llvm/CodeGen/MachineDominators.h"
19#include "llvm/CodeGen/MachineRegisterInfo.h"
20#include "llvm/CodeGen/Passes.h"
21#include "llvm/CodeGen/TargetSubtargetInfo.h"
22#include "llvm/Config/llvm-config.h"
23#include "llvm/InitializePasses.h"
24#include "llvm/Support/Debug.h"
25#include "llvm/Support/raw_ostream.h"
26
27using namespace llvm;
28
29// Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
30template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
31template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
32
33char MachineLoopInfo::ID = 0;
34MachineLoopInfo::MachineLoopInfo() : MachineFunctionPass(ID) {
35 initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
36}
37INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",static void *initializeMachineLoopInfoPassOnce(PassRegistry &
Registry) {
38 "Machine Natural Loop Construction", true, true)static void *initializeMachineLoopInfoPassOnce(PassRegistry &
Registry) {
39INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)initializeMachineDominatorTreePass(Registry);
40INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",PassInfo *PI = new PassInfo( "Machine Natural Loop Construction"
, "machine-loops", &MachineLoopInfo::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MachineLoopInfo>), true, true); Registry
.registerPass(*PI, true); return PI; } static llvm::once_flag
InitializeMachineLoopInfoPassFlag; void llvm::initializeMachineLoopInfoPass
(PassRegistry &Registry) { llvm::call_once(InitializeMachineLoopInfoPassFlag
, initializeMachineLoopInfoPassOnce, std::ref(Registry)); }
41 "Machine Natural Loop Construction", true, true)PassInfo *PI = new PassInfo( "Machine Natural Loop Construction"
, "machine-loops", &MachineLoopInfo::ID, PassInfo::NormalCtor_t
(callDefaultCtor<MachineLoopInfo>), true, true); Registry
.registerPass(*PI, true); return PI; } static llvm::once_flag
InitializeMachineLoopInfoPassFlag; void llvm::initializeMachineLoopInfoPass
(PassRegistry &Registry) { llvm::call_once(InitializeMachineLoopInfoPassFlag
, initializeMachineLoopInfoPassOnce, std::ref(Registry)); }
42
43char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
44
45bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
46 calculate(getAnalysis<MachineDominatorTree>());
47 return false;
48}
49
50void MachineLoopInfo::calculate(MachineDominatorTree &MDT) {
51 releaseMemory();
52 LI.analyze(MDT.getBase());
53}
54
55void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
56 AU.setPreservesAll();
57 AU.addRequired<MachineDominatorTree>();
58 MachineFunctionPass::getAnalysisUsage(AU);
59}
60
61MachineBasicBlock *MachineLoop::getTopBlock() {
62 MachineBasicBlock *TopMBB = getHeader();
63 MachineFunction::iterator Begin = TopMBB->getParent()->begin();
64 if (TopMBB->getIterator() != Begin) {
65 MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator());
66 while (contains(PriorMBB)) {
67 TopMBB = PriorMBB;
68 if (TopMBB->getIterator() == Begin)
69 break;
70 PriorMBB = &*std::prev(TopMBB->getIterator());
71 }
72 }
73 return TopMBB;
74}
75
76MachineBasicBlock *MachineLoop::getBottomBlock() {
77 MachineBasicBlock *BotMBB = getHeader();
78 MachineFunction::iterator End = BotMBB->getParent()->end();
79 if (BotMBB->getIterator() != std::prev(End)) {
80 MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator());
81 while (contains(NextMBB)) {
82 BotMBB = NextMBB;
83 if (BotMBB == &*std::next(BotMBB->getIterator()))
84 break;
85 NextMBB = &*std::next(BotMBB->getIterator());
86 }
87 }
88 return BotMBB;
89}
90
91MachineBasicBlock *MachineLoop::findLoopControlBlock() {
92 if (MachineBasicBlock *Latch = getLoopLatch()) {
93 if (isLoopExiting(Latch))
94 return Latch;
95 else
96 return getExitingBlock();
97 }
98 return nullptr;
99}
100
101DebugLoc MachineLoop::getStartLoc() const {
102 // Try the pre-header first.
103 if (MachineBasicBlock *PHeadMBB = getLoopPreheader())
104 if (const BasicBlock *PHeadBB = PHeadMBB->getBasicBlock())
105 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
106 return DL;
107
108 // If we have no pre-header or there are no instructions with debug
109 // info in it, try the header.
110 if (MachineBasicBlock *HeadMBB = getHeader())
111 if (const BasicBlock *HeadBB = HeadMBB->getBasicBlock())
112 return HeadBB->getTerminator()->getDebugLoc();
113
114 return DebugLoc();
115}
116
117MachineBasicBlock *
118MachineLoopInfo::findLoopPreheader(MachineLoop *L, bool SpeculativePreheader,
119 bool FindMultiLoopPreheader) const {
120 if (MachineBasicBlock *PB = L->getLoopPreheader())
1
Assuming 'PB' is null
2
Taking false branch
121 return PB;
122
123 if (!SpeculativePreheader)
3
Assuming 'SpeculativePreheader' is true
4
Taking false branch
124 return nullptr;
125
126 MachineBasicBlock *HB = L->getHeader(), *LB = L->getLoopLatch();
127 if (HB->pred_size() != 2 || HB->hasAddressTaken())
5
Assuming the condition is false
6
Assuming the condition is false
7
Taking false branch
128 return nullptr;
129 // Find the predecessor of the header that is not the latch block.
130 MachineBasicBlock *Preheader = nullptr;
8
'Preheader' initialized to a null pointer value
131 for (MachineBasicBlock *P : HB->predecessors()) {
132 if (P == LB)
133 continue;
134 // Sanity.
135 if (Preheader)
136 return nullptr;
137 Preheader = P;
138 }
139
140 // Check if the preheader candidate is a successor of any other loop
141 // headers. We want to avoid having two loop setups in the same block.
142 if (!FindMultiLoopPreheader) {
9
Assuming 'FindMultiLoopPreheader' is false
10
Taking true branch
143 for (MachineBasicBlock *S : Preheader->successors()) {
11
Called C++ object pointer is null
144 if (S == HB)
145 continue;
146 MachineLoop *T = getLoopFor(S);
147 if (T && T->getHeader() == S)
148 return nullptr;
149 }
150 }
151 return Preheader;
152}
153
154bool MachineLoop::isLoopInvariant(MachineInstr &I) const {
155 MachineFunction *MF = I.getParent()->getParent();
156 MachineRegisterInfo *MRI = &MF->getRegInfo();
157 const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
158
159 // The instruction is loop invariant if all of its operands are.
160 for (const MachineOperand &MO : I.operands()) {
161 if (!MO.isReg())
162 continue;
163
164 Register Reg = MO.getReg();
165 if (Reg == 0) continue;
166
167 // An instruction that uses or defines a physical register can't e.g. be
168 // hoisted, so mark this as not invariant.
169 if (Register::isPhysicalRegister(Reg)) {
170 if (MO.isUse()) {
171 // If the physreg has no defs anywhere, it's just an ambient register
172 // and we can freely move its uses. Alternatively, if it's allocatable,
173 // it could get allocated to something with a def during allocation.
174 // However, if the physreg is known to always be caller saved/restored
175 // then this use is safe to hoist.
176 if (!MRI->isConstantPhysReg(Reg) &&
177 !(TRI->isCallerPreservedPhysReg(Reg.asMCReg(), *I.getMF())))
178 return false;
179 // Otherwise it's safe to move.
180 continue;
181 } else if (!MO.isDead()) {
182 // A def that isn't dead can't be moved.
183 return false;
184 } else if (getHeader()->isLiveIn(Reg)) {
185 // If the reg is live into the loop, we can't hoist an instruction
186 // which would clobber it.
187 return false;
188 }
189 }
190
191 if (!MO.isUse())
192 continue;
193
194 assert(MRI->getVRegDef(Reg) &&(static_cast<void> (0))
195 "Machine instr not mapped for this vreg?!")(static_cast<void> (0));
196
197 // If the loop contains the definition of an operand, then the instruction
198 // isn't loop invariant.
199 if (contains(MRI->getVRegDef(Reg)))
200 return false;
201 }
202
203 // If we got this far, the instruction is loop invariant!
204 return true;
205}
206
207#if !defined(NDEBUG1) || defined(LLVM_ENABLE_DUMP)
208LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void MachineLoop::dump() const {
209 print(dbgs());
210}
211#endif