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1 //===-- HexagonCFGOptimizer.cpp - CFG optimizations -----------------------===//
2 // The LLVM Compiler Infrastructure
4 // This file is distributed under the University of Illinois Open Source
5 // License. See LICENSE.TXT for details.
7 //===----------------------------------------------------------------------===//
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"
28 #define DEBUG_TYPE "hexagon_cfg"
31 void initializeHexagonCFGOptimizerPass(PassRegistry
&);
37 class HexagonCFGOptimizer
: public MachineFunctionPass
{
40 const HexagonTargetMachine
& QTM
;
41 const HexagonSubtarget
&QST
;
43 void InvertAndChangeJumpTarget(MachineInstr
*, MachineBasicBlock
*);
47 HexagonCFGOptimizer(const HexagonTargetMachine
& TM
)
48 : MachineFunctionPass(ID
), QTM(TM
), QST(*TM
.getSubtargetImpl()) {
49 initializeHexagonCFGOptimizerPass(*PassRegistry::getPassRegistry());
52 const char *getPassName() const override
{
53 return "Hexagon CFG Optimizer";
55 bool runOnMachineFunction(MachineFunction
&Fn
) override
;
59 char HexagonCFGOptimizer::ID
= 0;
61 static bool IsConditionalBranch(int Opc
) {
62 return (Opc
== Hexagon::J2_jumpt
) || (Opc
== Hexagon::J2_jumpf
)
63 || (Opc
== Hexagon::J2_jumptnewpt
) || (Opc
== Hexagon::J2_jumpfnewpt
);
67 static bool IsUnconditionalJump(int Opc
) {
68 return (Opc
== Hexagon::J2_jump
);
73 HexagonCFGOptimizer::InvertAndChangeJumpTarget(MachineInstr
* MI
,
74 MachineBasicBlock
* NewTarget
) {
75 const HexagonInstrInfo
*QII
= QTM
.getSubtargetImpl()->getInstrInfo();
77 switch(MI
->getOpcode()) {
78 case Hexagon::J2_jumpt
:
79 NewOpcode
= Hexagon::J2_jumpf
;
82 case Hexagon::J2_jumpf
:
83 NewOpcode
= Hexagon::J2_jumpt
;
86 case Hexagon::J2_jumptnewpt
:
87 NewOpcode
= Hexagon::J2_jumpfnewpt
;
90 case Hexagon::J2_jumpfnewpt
:
91 NewOpcode
= Hexagon::J2_jumptnewpt
;
95 llvm_unreachable("Cannot handle this case");
98 MI
->setDesc(QII
->get(NewOpcode
));
99 MI
->getOperand(1).setMBB(NewTarget
);
103 bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction
&Fn
) {
105 // Loop over all of the basic blocks.
106 for (MachineFunction::iterator MBBb
= Fn
.begin(), MBBe
= Fn
.end();
107 MBBb
!= MBBe
; ++MBBb
) {
108 MachineBasicBlock
* MBB
= MBBb
;
110 // Traverse the basic block.
111 MachineBasicBlock::iterator MII
= MBB
->getFirstTerminator();
112 if (MII
!= MBB
->end()) {
113 MachineInstr
*MI
= MII
;
114 int Opc
= MI
->getOpcode();
115 if (IsConditionalBranch(Opc
)) {
118 // (Case 1) Transform the code if the following condition occurs:
119 // BB1: if (p0) jump BB3
120 // ...falls-through to BB2 ...
122 // ...next block in layout is BB3...
125 // Transform this to:
126 // BB1: if (!p0) jump BB4
130 // (Case 2) A variation occurs when BB3 contains a JMP to BB4:
131 // BB1: if (p0) jump BB3
132 // ...falls-through to BB2 ...
134 // ...other basic blocks ...
136 // ...not a fall-thru
140 // Transform this to:
141 // BB1: if (!p0) jump BB4
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;
153 if (MBB
->isLayoutSuccessor(FirstSucc
)) {
154 LayoutSucc
= FirstSucc
;
155 JumpAroundTarget
= SecondSucc
;
156 } else if (MBB
->isLayoutSuccessor(SecondSucc
)) {
157 LayoutSucc
= SecondSucc
;
158 JumpAroundTarget
= FirstSucc
;
160 // Odd case...cannot handle.
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
) ||
167 (MI
->getOpcode() == Hexagon::J2_jumpf
)) {
168 CondBranchTarget
= MI
->getOperand(1).getMBB();
171 if (!LayoutSucc
|| (CondBranchTarget
!= JumpAroundTarget
)) {
175 if ((NumSuccs
== 2) && LayoutSucc
&& (LayoutSucc
->pred_size() == 1)) {
177 // Ensure that BB2 has one instruction -- an unconditional jump.
178 if ((LayoutSucc
->size() == 1) &&
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
) &&
185 JumpAroundTarget
->size() >= 1 &&
186 IsUnconditionalJump(JumpAroundTarget
->back().getOpcode()) &&
187 JumpAroundTarget
->pred_size() == 1 &&
188 JumpAroundTarget
->succ_size() == 1;
190 if (case1
|| case2
) {
191 InvertAndChangeJumpTarget(MI
, UncondTarget
);
192 MBB
->removeSuccessor(JumpAroundTarget
);
193 MBB
->addSuccessor(UncondTarget
);
195 // Remove the unconditional branch in LayoutSucc.
196 LayoutSucc
->erase(LayoutSucc
->begin());
197 LayoutSucc
->removeSuccessor(UncondTarget
);
198 LayoutSucc
->addSuccessor(JumpAroundTarget
);
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
);
212 // Correct live-in information. Is used by post-RA scheduler
213 // The live-in to LayoutSucc is now all values live-in to
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
]);
223 for (unsigned i
= 0; i
< NewLiveIn
.size(); ++i
) {
224 LayoutSucc
->addLiveIn(NewLiveIn
[i
]);
237 //===----------------------------------------------------------------------===//
238 // Public Constructor Functions
239 //===----------------------------------------------------------------------===//
241 static 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);
247 void llvm::initializeHexagonCFGOptimizerPass(PassRegistry
&Registry
) {
248 CALL_ONCE_INITIALIZATION(initializePassOnce
)
251 FunctionPass
*llvm::createHexagonCFGOptimizer(const HexagonTargetMachine
&TM
) {
252 return new HexagonCFGOptimizer(TM
);