Bug Summary

File:llvm/lib/CodeGen/MachineLoopInfo.cpp
Warning:line 135, column 31
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 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 -mthread-model posix -mframe-pointer=none -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -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~+201911111502510600c19528f1809/build-llvm/lib/CodeGen -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/llvm/lib/CodeGen -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/build-llvm/include -I /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/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~+201911111502510600c19528f1809/build-llvm/lib/CodeGen -fdebug-prefix-map=/build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809=. -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-2019-12-11-181444-25759-1 -x c++ /build/llvm-toolchain-snapshot-10~+201911111502510600c19528f1809/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/Passes.h"
20#include "llvm/Config/llvm-config.h"
21#include "llvm/Support/Debug.h"
22#include "llvm/Support/raw_ostream.h"
23using namespace llvm;
24
25// Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
26template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
27template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
28
29char MachineLoopInfo::ID = 0;
30INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",static void *initializeMachineLoopInfoPassOnce(PassRegistry &
Registry) {
31 "Machine Natural Loop Construction", true, true)static void *initializeMachineLoopInfoPassOnce(PassRegistry &
Registry) {
32INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)initializeMachineDominatorTreePass(Registry);
33INITIALIZE_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)); }
34 "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)); }
35
36char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
37
38bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
39 calculate(getAnalysis<MachineDominatorTree>());
40 return false;
41}
42
43void MachineLoopInfo::calculate(MachineDominatorTree &MDT) {
44 releaseMemory();
45 LI.analyze(MDT.getBase());
46}
47
48void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
49 AU.setPreservesAll();
50 AU.addRequired<MachineDominatorTree>();
51 MachineFunctionPass::getAnalysisUsage(AU);
52}
53
54MachineBasicBlock *MachineLoop::getTopBlock() {
55 MachineBasicBlock *TopMBB = getHeader();
56 MachineFunction::iterator Begin = TopMBB->getParent()->begin();
57 if (TopMBB->getIterator() != Begin) {
58 MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator());
59 while (contains(PriorMBB)) {
60 TopMBB = PriorMBB;
61 if (TopMBB->getIterator() == Begin)
62 break;
63 PriorMBB = &*std::prev(TopMBB->getIterator());
64 }
65 }
66 return TopMBB;
67}
68
69MachineBasicBlock *MachineLoop::getBottomBlock() {
70 MachineBasicBlock *BotMBB = getHeader();
71 MachineFunction::iterator End = BotMBB->getParent()->end();
72 if (BotMBB->getIterator() != std::prev(End)) {
73 MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator());
74 while (contains(NextMBB)) {
75 BotMBB = NextMBB;
76 if (BotMBB == &*std::next(BotMBB->getIterator()))
77 break;
78 NextMBB = &*std::next(BotMBB->getIterator());
79 }
80 }
81 return BotMBB;
82}
83
84MachineBasicBlock *MachineLoop::findLoopControlBlock() {
85 if (MachineBasicBlock *Latch = getLoopLatch()) {
86 if (isLoopExiting(Latch))
87 return Latch;
88 else
89 return getExitingBlock();
90 }
91 return nullptr;
92}
93
94DebugLoc MachineLoop::getStartLoc() const {
95 // Try the pre-header first.
96 if (MachineBasicBlock *PHeadMBB = getLoopPreheader())
97 if (const BasicBlock *PHeadBB = PHeadMBB->getBasicBlock())
98 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
99 return DL;
100
101 // If we have no pre-header or there are no instructions with debug
102 // info in it, try the header.
103 if (MachineBasicBlock *HeadMBB = getHeader())
104 if (const BasicBlock *HeadBB = HeadMBB->getBasicBlock())
105 return HeadBB->getTerminator()->getDebugLoc();
106
107 return DebugLoc();
108}
109
110MachineBasicBlock *
111MachineLoopInfo::findLoopPreheader(MachineLoop *L,
112 bool SpeculativePreheader) const {
113 if (MachineBasicBlock *PB = L->getLoopPreheader())
1
Assuming 'PB' is null
2
Taking false branch
114 return PB;
115
116 if (!SpeculativePreheader)
3
Assuming 'SpeculativePreheader' is true
4
Taking false branch
117 return nullptr;
118
119 MachineBasicBlock *HB = L->getHeader(), *LB = L->getLoopLatch();
120 if (HB->pred_size() != 2 || HB->hasAddressTaken())
5
Assuming the condition is false
6
Assuming the condition is false
7
Taking false branch
121 return nullptr;
122 // Find the predecessor of the header that is not the latch block.
123 MachineBasicBlock *Preheader = nullptr;
8
'Preheader' initialized to a null pointer value
124 for (MachineBasicBlock *P : HB->predecessors()) {
125 if (P == LB)
126 continue;
127 // Sanity.
128 if (Preheader)
129 return nullptr;
130 Preheader = P;
131 }
132
133 // Check if the preheader candidate is a successor of any other loop
134 // headers. We want to avoid having two loop setups in the same block.
135 for (MachineBasicBlock *S : Preheader->successors()) {
9
Called C++ object pointer is null
136 if (S == HB)
137 continue;
138 MachineLoop *T = getLoopFor(S);
139 if (T && T->getHeader() == S)
140 return nullptr;
141 }
142 return Preheader;
143}
144
145#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
146LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void MachineLoop::dump() const {
147 print(dbgs());
148}
149#endif