|
150
|
1 //===- HexagonCFGOptimizer.cpp - CFG optimizations ------------------------===//
|
|
|
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 "Hexagon.h"
|
|
|
10 #include "llvm/CodeGen/MachineBasicBlock.h"
|
|
|
11 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
|
|
|
12 #include "llvm/CodeGen/MachineFunction.h"
|
|
|
13 #include "llvm/CodeGen/MachineFunctionPass.h"
|
|
|
14 #include "llvm/CodeGen/MachineInstr.h"
|
|
|
15 #include "llvm/CodeGen/MachineOperand.h"
|
|
|
16 #include "llvm/CodeGen/TargetInstrInfo.h"
|
|
|
17 #include "llvm/CodeGen/TargetSubtargetInfo.h"
|
|
|
18 #include "llvm/Pass.h"
|
|
|
19 #include "llvm/Support/ErrorHandling.h"
|
|
|
20 #include <cassert>
|
|
|
21 #include <vector>
|
|
|
22
|
|
|
23 using namespace llvm;
|
|
|
24
|
|
|
25 #define DEBUG_TYPE "hexagon_cfg"
|
|
|
26
|
|
|
27 namespace llvm {
|
|
|
28
|
|
|
29 FunctionPass *createHexagonCFGOptimizer();
|
|
|
30 void initializeHexagonCFGOptimizerPass(PassRegistry&);
|
|
|
31
|
|
|
32 } // end namespace llvm
|
|
|
33
|
|
|
34 namespace {
|
|
|
35
|
|
|
36 class HexagonCFGOptimizer : public MachineFunctionPass {
|
|
|
37 private:
|
|
|
38 void InvertAndChangeJumpTarget(MachineInstr &, MachineBasicBlock *);
|
|
|
39 bool isOnFallThroughPath(MachineBasicBlock *MBB);
|
|
|
40
|
|
|
41 public:
|
|
|
42 static char ID;
|
|
|
43
|
|
|
44 HexagonCFGOptimizer() : MachineFunctionPass(ID) {
|
|
|
45 initializeHexagonCFGOptimizerPass(*PassRegistry::getPassRegistry());
|
|
|
46 }
|
|
|
47
|
|
|
48 StringRef getPassName() const override { return "Hexagon CFG Optimizer"; }
|
|
|
49 bool runOnMachineFunction(MachineFunction &Fn) override;
|
|
|
50
|
|
|
51 MachineFunctionProperties getRequiredProperties() const override {
|
|
|
52 return MachineFunctionProperties().set(
|
|
|
53 MachineFunctionProperties::Property::NoVRegs);
|
|
|
54 }
|
|
|
55 };
|
|
|
56
|
|
|
57 } // end anonymous namespace
|
|
|
58
|
|
|
59 char HexagonCFGOptimizer::ID = 0;
|
|
|
60
|
|
|
61 static bool IsConditionalBranch(int Opc) {
|
|
|
62 switch (Opc) {
|
|
|
63 case Hexagon::J2_jumpt:
|
|
|
64 case Hexagon::J2_jumptpt:
|
|
|
65 case Hexagon::J2_jumpf:
|
|
|
66 case Hexagon::J2_jumpfpt:
|
|
|
67 case Hexagon::J2_jumptnew:
|
|
|
68 case Hexagon::J2_jumpfnew:
|
|
|
69 case Hexagon::J2_jumptnewpt:
|
|
|
70 case Hexagon::J2_jumpfnewpt:
|
|
|
71 return true;
|
|
|
72 }
|
|
|
73 return false;
|
|
|
74 }
|
|
|
75
|
|
|
76 static bool IsUnconditionalJump(int Opc) {
|
|
|
77 return (Opc == Hexagon::J2_jump);
|
|
|
78 }
|
|
|
79
|
|
|
80 void HexagonCFGOptimizer::InvertAndChangeJumpTarget(
|
|
|
81 MachineInstr &MI, MachineBasicBlock *NewTarget) {
|
|
|
82 const TargetInstrInfo *TII =
|
|
|
83 MI.getParent()->getParent()->getSubtarget().getInstrInfo();
|
|
|
84 int NewOpcode = 0;
|
|
|
85 switch (MI.getOpcode()) {
|
|
|
86 case Hexagon::J2_jumpt:
|
|
|
87 NewOpcode = Hexagon::J2_jumpf;
|
|
|
88 break;
|
|
|
89 case Hexagon::J2_jumpf:
|
|
|
90 NewOpcode = Hexagon::J2_jumpt;
|
|
|
91 break;
|
|
|
92 case Hexagon::J2_jumptnewpt:
|
|
|
93 NewOpcode = Hexagon::J2_jumpfnewpt;
|
|
|
94 break;
|
|
|
95 case Hexagon::J2_jumpfnewpt:
|
|
|
96 NewOpcode = Hexagon::J2_jumptnewpt;
|
|
|
97 break;
|
|
|
98 default:
|
|
|
99 llvm_unreachable("Cannot handle this case");
|
|
|
100 }
|
|
|
101
|
|
|
102 MI.setDesc(TII->get(NewOpcode));
|
|
|
103 MI.getOperand(1).setMBB(NewTarget);
|
|
|
104 }
|
|
|
105
|
|
|
106 bool HexagonCFGOptimizer::isOnFallThroughPath(MachineBasicBlock *MBB) {
|
|
|
107 if (MBB->canFallThrough())
|
|
|
108 return true;
|
|
|
109 for (MachineBasicBlock *PB : MBB->predecessors())
|
|
|
110 if (PB->isLayoutSuccessor(MBB) && PB->canFallThrough())
|
|
|
111 return true;
|
|
|
112 return false;
|
|
|
113 }
|
|
|
114
|
|
|
115 bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
|
|
|
116 if (skipFunction(Fn.getFunction()))
|
|
|
117 return false;
|
|
|
118
|
|
|
119 // Loop over all of the basic blocks.
|
|
|
120 for (MachineFunction::iterator MBBb = Fn.begin(), MBBe = Fn.end();
|
|
|
121 MBBb != MBBe; ++MBBb) {
|
|
|
122 MachineBasicBlock *MBB = &*MBBb;
|
|
|
123
|
|
|
124 // Traverse the basic block.
|
|
|
125 MachineBasicBlock::iterator MII = MBB->getFirstTerminator();
|
|
|
126 if (MII != MBB->end()) {
|
|
|
127 MachineInstr &MI = *MII;
|
|
|
128 int Opc = MI.getOpcode();
|
|
|
129 if (IsConditionalBranch(Opc)) {
|
|
|
130 // (Case 1) Transform the code if the following condition occurs:
|
|
|
131 // BB1: if (p0) jump BB3
|
|
|
132 // ...falls-through to BB2 ...
|
|
|
133 // BB2: jump BB4
|
|
|
134 // ...next block in layout is BB3...
|
|
|
135 // BB3: ...
|
|
|
136 //
|
|
|
137 // Transform this to:
|
|
|
138 // BB1: if (!p0) jump BB4
|
|
|
139 // Remove BB2
|
|
|
140 // BB3: ...
|
|
|
141 //
|
|
|
142 // (Case 2) A variation occurs when BB3 contains a JMP to BB4:
|
|
|
143 // BB1: if (p0) jump BB3
|
|
|
144 // ...falls-through to BB2 ...
|
|
|
145 // BB2: jump BB4
|
|
|
146 // ...other basic blocks ...
|
|
|
147 // BB4:
|
|
|
148 // ...not a fall-thru
|
|
|
149 // BB3: ...
|
|
|
150 // jump BB4
|
|
|
151 //
|
|
|
152 // Transform this to:
|
|
|
153 // BB1: if (!p0) jump BB4
|
|
|
154 // Remove BB2
|
|
|
155 // BB3: ...
|
|
|
156 // BB4: ...
|
|
|
157 unsigned NumSuccs = MBB->succ_size();
|
|
|
158 MachineBasicBlock::succ_iterator SI = MBB->succ_begin();
|
|
|
159 MachineBasicBlock* FirstSucc = *SI;
|
|
|
160 MachineBasicBlock* SecondSucc = *(++SI);
|
|
|
161 MachineBasicBlock* LayoutSucc = nullptr;
|
|
|
162 MachineBasicBlock* JumpAroundTarget = nullptr;
|
|
|
163
|
|
|
164 if (MBB->isLayoutSuccessor(FirstSucc)) {
|
|
|
165 LayoutSucc = FirstSucc;
|
|
|
166 JumpAroundTarget = SecondSucc;
|
|
|
167 } else if (MBB->isLayoutSuccessor(SecondSucc)) {
|
|
|
168 LayoutSucc = SecondSucc;
|
|
|
169 JumpAroundTarget = FirstSucc;
|
|
|
170 } else {
|
|
|
171 // Odd case...cannot handle.
|
|
|
172 }
|
|
|
173
|
|
|
174 // The target of the unconditional branch must be JumpAroundTarget.
|
|
|
175 // TODO: If not, we should not invert the unconditional branch.
|
|
|
176 MachineBasicBlock* CondBranchTarget = nullptr;
|
|
|
177 if (MI.getOpcode() == Hexagon::J2_jumpt ||
|
|
|
178 MI.getOpcode() == Hexagon::J2_jumpf) {
|
|
|
179 CondBranchTarget = MI.getOperand(1).getMBB();
|
|
|
180 }
|
|
|
181
|
|
|
182 if (!LayoutSucc || (CondBranchTarget != JumpAroundTarget)) {
|
|
|
183 continue;
|
|
|
184 }
|
|
|
185
|
|
|
186 if ((NumSuccs == 2) && LayoutSucc && (LayoutSucc->pred_size() == 1)) {
|
|
|
187 // Ensure that BB2 has one instruction -- an unconditional jump.
|
|
|
188 if ((LayoutSucc->size() == 1) &&
|
|
|
189 IsUnconditionalJump(LayoutSucc->front().getOpcode())) {
|
|
|
190 assert(JumpAroundTarget && "jump target is needed to process second basic block");
|
|
|
191 MachineBasicBlock* UncondTarget =
|
|
|
192 LayoutSucc->front().getOperand(0).getMBB();
|
|
|
193 // Check if the layout successor of BB2 is BB3.
|
|
|
194 bool case1 = LayoutSucc->isLayoutSuccessor(JumpAroundTarget);
|
|
|
195 bool case2 = JumpAroundTarget->isSuccessor(UncondTarget) &&
|
|
|
196 !JumpAroundTarget->empty() &&
|
|
|
197 IsUnconditionalJump(JumpAroundTarget->back().getOpcode()) &&
|
|
|
198 JumpAroundTarget->pred_size() == 1 &&
|
|
|
199 JumpAroundTarget->succ_size() == 1;
|
|
|
200
|
|
|
201 if (case1 || case2) {
|
|
|
202 InvertAndChangeJumpTarget(MI, UncondTarget);
|
|
|
203 MBB->replaceSuccessor(JumpAroundTarget, UncondTarget);
|
|
|
204
|
|
|
205 // Remove the unconditional branch in LayoutSucc.
|
|
|
206 LayoutSucc->erase(LayoutSucc->begin());
|
|
|
207 LayoutSucc->replaceSuccessor(UncondTarget, JumpAroundTarget);
|
|
|
208
|
|
|
209 // This code performs the conversion for case 2, which moves
|
|
|
210 // the block to the fall-thru case (BB3 in the code above).
|
|
|
211 if (case2 && !case1) {
|
|
|
212 JumpAroundTarget->moveAfter(LayoutSucc);
|
|
|
213 // only move a block if it doesn't have a fall-thru. otherwise
|
|
|
214 // the CFG will be incorrect.
|
|
|
215 if (!isOnFallThroughPath(UncondTarget))
|
|
|
216 UncondTarget->moveAfter(JumpAroundTarget);
|
|
|
217 }
|
|
|
218
|
|
|
219 // Correct live-in information. Is used by post-RA scheduler
|
|
|
220 // The live-in to LayoutSucc is now all values live-in to
|
|
|
221 // JumpAroundTarget.
|
|
|
222 std::vector<MachineBasicBlock::RegisterMaskPair> OrigLiveIn(
|
|
|
223 LayoutSucc->livein_begin(), LayoutSucc->livein_end());
|
|
|
224 std::vector<MachineBasicBlock::RegisterMaskPair> NewLiveIn(
|
|
|
225 JumpAroundTarget->livein_begin(),
|
|
|
226 JumpAroundTarget->livein_end());
|
|
|
227 for (const auto &OrigLI : OrigLiveIn)
|
|
|
228 LayoutSucc->removeLiveIn(OrigLI.PhysReg);
|
|
|
229 for (const auto &NewLI : NewLiveIn)
|
|
|
230 LayoutSucc->addLiveIn(NewLI);
|
|
|
231 }
|
|
|
232 }
|
|
|
233 }
|
|
|
234 }
|
|
|
235 }
|
|
|
236 }
|
|
|
237 return true;
|
|
|
238 }
|
|
|
239
|
|
|
240 //===----------------------------------------------------------------------===//
|
|
|
241 // Public Constructor Functions
|
|
|
242 //===----------------------------------------------------------------------===//
|
|
|
243
|
|
|
244 INITIALIZE_PASS(HexagonCFGOptimizer, "hexagon-cfg", "Hexagon CFG Optimizer",
|
|
|
245 false, false)
|
|
|
246
|
|
|
247 FunctionPass *llvm::createHexagonCFGOptimizer() {
|
|
|
248 return new HexagonCFGOptimizer();
|
|
|
249 }
|
