Bug Summary

File:lib/Target/Hexagon/HexagonCFGOptimizer.cpp
Location:line 184, column 26
Description:Called C++ object pointer is null

Annotated Source Code

1//===-- HexagonCFGOptimizer.cpp - CFG optimizations -----------------------===//
2// The LLVM Compiler Infrastructure
3//
4// This file is distributed under the University of Illinois Open Source
5// License. See LICENSE.TXT for details.
6//
7//===----------------------------------------------------------------------===//
8
9#include "Hexagon.h"
10#include "HexagonMachineFunctionInfo.h"
11#include "HexagonSubtarget.h"
12#include "HexagonTargetMachine.h"
13#include "llvm/CodeGen/MachineDominators.h"
14#include "llvm/CodeGen/MachineFunctionPass.h"
15#include "llvm/CodeGen/MachineInstrBuilder.h"
16#include "llvm/CodeGen/MachineLoopInfo.h"
17#include "llvm/CodeGen/MachineRegisterInfo.h"
18#include "llvm/CodeGen/Passes.h"
19#include "llvm/Support/Compiler.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/Support/MathExtras.h"
22#include "llvm/Target/TargetInstrInfo.h"
23#include "llvm/Target/TargetMachine.h"
24#include "llvm/Target/TargetRegisterInfo.h"
25
26using namespace llvm;
27
28#define DEBUG_TYPE"hexagon_cfg" "hexagon_cfg"
29
30namespace llvm {
31 void initializeHexagonCFGOptimizerPass(PassRegistry&);
32}
33
34
35namespace {
36
37class HexagonCFGOptimizer : public MachineFunctionPass {
38
39private:
40 const HexagonTargetMachine& QTM;
41 const HexagonSubtarget &QST;
42
43 void InvertAndChangeJumpTarget(MachineInstr*, MachineBasicBlock*);
44
45 public:
46 static char ID;
47 HexagonCFGOptimizer(const HexagonTargetMachine& TM)
48 : MachineFunctionPass(ID), QTM(TM), QST(*TM.getSubtargetImpl()) {
49 initializeHexagonCFGOptimizerPass(*PassRegistry::getPassRegistry());
50 }
51
52 const char *getPassName() const override {
53 return "Hexagon CFG Optimizer";
54 }
55 bool runOnMachineFunction(MachineFunction &Fn) override;
56};
57
58
59char HexagonCFGOptimizer::ID = 0;
60
61static bool IsConditionalBranch(int Opc) {
62 return (Opc == Hexagon::J2_jumpt) || (Opc == Hexagon::J2_jumpf)
63 || (Opc == Hexagon::J2_jumptnewpt) || (Opc == Hexagon::J2_jumpfnewpt);
64}
65
66
67static bool IsUnconditionalJump(int Opc) {
68 return (Opc == Hexagon::J2_jump);
69}
70
71
72void
73HexagonCFGOptimizer::InvertAndChangeJumpTarget(MachineInstr* MI,
74 MachineBasicBlock* NewTarget) {
75 const HexagonInstrInfo *QII = QTM.getSubtargetImpl()->getInstrInfo();
76 int NewOpcode = 0;
77 switch(MI->getOpcode()) {
78 case Hexagon::J2_jumpt:
79 NewOpcode = Hexagon::J2_jumpf;
80 break;
81
82 case Hexagon::J2_jumpf:
83 NewOpcode = Hexagon::J2_jumpt;
84 break;
85
86 case Hexagon::J2_jumptnewpt:
87 NewOpcode = Hexagon::J2_jumpfnewpt;
88 break;
89
90 case Hexagon::J2_jumpfnewpt:
91 NewOpcode = Hexagon::J2_jumptnewpt;
92 break;
93
94 default:
95 llvm_unreachable("Cannot handle this case")::llvm::llvm_unreachable_internal("Cannot handle this case", "/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227765/lib/Target/Hexagon/HexagonCFGOptimizer.cpp"
, 95);
96 }
97
98 MI->setDesc(QII->get(NewOpcode));
99 MI->getOperand(1).setMBB(NewTarget);
100}
101
102
103bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
104
105 // Loop over all of the basic blocks.
106 for (MachineFunction::iterator MBBb = Fn.begin(), MBBe = Fn.end();
1
Loop condition is true. Entering loop body
→
3
←
Loop condition is true. Entering loop body
→
5
←
Loop condition is true. Entering loop body
→
7
←
Loop condition is true. Entering loop body
→
107 MBBb != MBBe; ++MBBb) {
108 MachineBasicBlock* MBB = MBBb;
109
110 // Traverse the basic block.
111 MachineBasicBlock::iterator MII = MBB->getFirstTerminator();
112 if (MII != MBB->end()) {
2
←
Taking false branch
→
4
←
Taking false branch
→
6
←
Taking false branch
→
8
←
Taking true branch
→
113 MachineInstr *MI = MII;
114 int Opc = MI->getOpcode();
115 if (IsConditionalBranch(Opc)) {
9
←
Taking true branch
→
116
117 //
118 // (Case 1) Transform the code if the following condition occurs:
119 // BB1: if (p0) jump BB3
120 // ...falls-through to BB2 ...
121 // BB2: jump BB4
122 // ...next block in layout is BB3...
123 // BB3: ...
124 //
125 // Transform this to:
126 // BB1: if (!p0) jump BB4
127 // Remove BB2
128 // BB3: ...
129 //
130 // (Case 2) A variation occurs when BB3 contains a JMP to BB4:
131 // BB1: if (p0) jump BB3
132 // ...falls-through to BB2 ...
133 // BB2: jump BB4
134 // ...other basic blocks ...
135 // BB4:
136 // ...not a fall-thru
137 // BB3: ...
138 // jump BB4
139 //
140 // Transform this to:
141 // BB1: if (!p0) jump BB4
142 // Remove BB2
143 // BB3: ...
144 // BB4: ...
145 //
146 unsigned NumSuccs = MBB->succ_size();
147 MachineBasicBlock::succ_iterator SI = MBB->succ_begin();
148 MachineBasicBlock* FirstSucc = *SI;
149 MachineBasicBlock* SecondSucc = *(++SI);
150 MachineBasicBlock* LayoutSucc = nullptr;
151 MachineBasicBlock* JumpAroundTarget = nullptr;
152
153 if (MBB->isLayoutSuccessor(FirstSucc)) {
10
←
Taking true branch
→
154 LayoutSucc = FirstSucc;
155 JumpAroundTarget = SecondSucc;
11
←
Value assigned to 'JumpAroundTarget'
→
156 } else if (MBB->isLayoutSuccessor(SecondSucc)) {
157 LayoutSucc = SecondSucc;
158 JumpAroundTarget = FirstSucc;
159 } else {
160 // Odd case...cannot handle.
161 }
162
163 // The target of the unconditional branch must be JumpAroundTarget.
164 // TODO: If not, we should not invert the unconditional branch.
165 MachineBasicBlock* CondBranchTarget = nullptr;
166 if ((MI->getOpcode() == Hexagon::J2_jumpt) ||
12
←
Taking false branch
→
167 (MI->getOpcode() == Hexagon::J2_jumpf)) {
168 CondBranchTarget = MI->getOperand(1).getMBB();
169 }
170
171 if (!LayoutSucc || (CondBranchTarget != JumpAroundTarget)) {
13
←
Assuming 'LayoutSucc' is non-null
→
14
←
Assuming 'CondBranchTarget' is equal to 'JumpAroundTarget'
→
15
←
Taking false branch
→
172 continue;
173 }
174
175 if ((NumSuccs == 2) && LayoutSucc && (LayoutSucc->pred_size() == 1)) {
16
←
Assuming 'NumSuccs' is equal to 2
→
17
←
Taking true branch
→
176
177 // Ensure that BB2 has one instruction -- an unconditional jump.
178 if ((LayoutSucc->size() == 1) &&
18
←
Taking true branch
→
179 IsUnconditionalJump(LayoutSucc->front().getOpcode())) {
180 MachineBasicBlock* UncondTarget =
181 LayoutSucc->front().getOperand(0).getMBB();
182 // Check if the layout successor of BB2 is BB3.
183 bool case1 = LayoutSucc->isLayoutSuccessor(JumpAroundTarget);
184 bool case2 = JumpAroundTarget->isSuccessor(UncondTarget) &&
19
←
Called C++ object pointer is null
185 JumpAroundTarget->size() >= 1 &&
186 IsUnconditionalJump(JumpAroundTarget->back().getOpcode()) &&
187 JumpAroundTarget->pred_size() == 1 &&
188 JumpAroundTarget->succ_size() == 1;
189
190 if (case1 || case2) {
191 InvertAndChangeJumpTarget(MI, UncondTarget);
192 MBB->removeSuccessor(JumpAroundTarget);
193 MBB->addSuccessor(UncondTarget);
194
195 // Remove the unconditional branch in LayoutSucc.
196 LayoutSucc->erase(LayoutSucc->begin());
197 LayoutSucc->removeSuccessor(UncondTarget);
198 LayoutSucc->addSuccessor(JumpAroundTarget);
199
200 // This code performs the conversion for case 2, which moves
201 // the block to the fall-thru case (BB3 in the code above).
202 if (case2 && !case1) {
203 JumpAroundTarget->moveAfter(LayoutSucc);
204 // only move a block if it doesn't have a fall-thru. otherwise
205 // the CFG will be incorrect.
206 if (!UncondTarget->canFallThrough()) {
207 UncondTarget->moveAfter(JumpAroundTarget);
208 }
209 }
210
211 //
212 // Correct live-in information. Is used by post-RA scheduler
213 // The live-in to LayoutSucc is now all values live-in to
214 // JumpAroundTarget.
215 //
216 std::vector<unsigned> OrigLiveIn(LayoutSucc->livein_begin(),
217 LayoutSucc->livein_end());
218 std::vector<unsigned> NewLiveIn(JumpAroundTarget->livein_begin(),
219 JumpAroundTarget->livein_end());
220 for (unsigned i = 0; i < OrigLiveIn.size(); ++i) {
221 LayoutSucc->removeLiveIn(OrigLiveIn[i]);
222 }
223 for (unsigned i = 0; i < NewLiveIn.size(); ++i) {
224 LayoutSucc->addLiveIn(NewLiveIn[i]);
225 }
226 }
227 }
228 }
229 }
230 }
231 }
232 return true;
233}
234}
235
236
237//===----------------------------------------------------------------------===//
238// Public Constructor Functions
239//===----------------------------------------------------------------------===//
240
241static void initializePassOnce(PassRegistry &Registry) {
242 PassInfo *PI = new PassInfo("Hexagon CFG Optimizer", "hexagon-cfg",
243 &HexagonCFGOptimizer::ID, nullptr, false, false);
244 Registry.registerPass(*PI, true);
245}
246
247void llvm::initializeHexagonCFGOptimizerPass(PassRegistry &Registry) {
248 CALL_ONCE_INITIALIZATION(initializePassOnce)static volatile sys::cas_flag initialized = 0; sys::cas_flag old_val
= sys::CompareAndSwap(&initialized, 1, 0); if (old_val ==
0) { initializePassOnce(Registry); sys::MemoryFence(); AnnotateIgnoreWritesBegin
("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227765/lib/Target/Hexagon/HexagonCFGOptimizer.cpp"
, 248); AnnotateHappensBefore("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227765/lib/Target/Hexagon/HexagonCFGOptimizer.cpp"
, 248, &initialized); initialized = 2; AnnotateIgnoreWritesEnd
("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227765/lib/Target/Hexagon/HexagonCFGOptimizer.cpp"
, 248); } else { sys::cas_flag tmp = initialized; sys::MemoryFence
(); while (tmp != 2) { tmp = initialized; sys::MemoryFence();
} } AnnotateHappensAfter("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227765/lib/Target/Hexagon/HexagonCFGOptimizer.cpp"
, 248, &initialized);
249}
250
251FunctionPass *llvm::createHexagonCFGOptimizer(const HexagonTargetMachine &TM) {
252 return new HexagonCFGOptimizer(TM);
253}