1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
//===-- LowerSubregs.cpp - Subregister Lowering instruction pass ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a MachineFunction pass which runs after register
// allocation that turns subreg insert/extract instructions into register
// copies, as needed. This ensures correct codegen even if the coalescer
// isn't able to remove all subreg instructions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lowersubregs"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
struct LowerSubregsInstructionPass : public MachineFunctionPass {
private:
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
public:
static char ID; // Pass identification, replacement for typeid
LowerSubregsInstructionPass() : MachineFunctionPass(ID) {}
const char *getPassName() const {
return "Subregister lowering instruction pass";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
/// runOnMachineFunction - pass entry point
bool runOnMachineFunction(MachineFunction&);
private:
bool LowerSubregToReg(MachineInstr *MI);
bool LowerCopy(MachineInstr *MI);
void TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
const TargetRegisterInfo *TRI);
void TransferImplicitDefs(MachineInstr *MI);
};
char LowerSubregsInstructionPass::ID = 0;
}
FunctionPass *llvm::createLowerSubregsPass() {
return new LowerSubregsInstructionPass();
}
/// TransferDeadFlag - MI is a pseudo-instruction with DstReg dead,
/// and the lowered replacement instructions immediately precede it.
/// Mark the replacement instructions with the dead flag.
void
LowerSubregsInstructionPass::TransferDeadFlag(MachineInstr *MI,
unsigned DstReg,
const TargetRegisterInfo *TRI) {
for (MachineBasicBlock::iterator MII =
prior(MachineBasicBlock::iterator(MI)); ; --MII) {
if (MII->addRegisterDead(DstReg, TRI))
break;
assert(MII != MI->getParent()->begin() &&
"copyPhysReg output doesn't reference destination register!");
}
}
/// TransferImplicitDefs - MI is a pseudo-instruction, and the lowered
/// replacement instructions immediately precede it. Copy any implicit-def
/// operands from MI to the replacement instruction.
void
LowerSubregsInstructionPass::TransferImplicitDefs(MachineInstr *MI) {
MachineBasicBlock::iterator CopyMI = MI;
--CopyMI;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isImplicit() || MO.isUse())
continue;
CopyMI->addOperand(MachineOperand::CreateReg(MO.getReg(), true, true));
}
}
bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) {
MachineBasicBlock *MBB = MI->getParent();
assert((MI->getOperand(0).isReg() && MI->getOperand(0).isDef()) &&
MI->getOperand(1).isImm() &&
(MI->getOperand(2).isReg() && MI->getOperand(2).isUse()) &&
MI->getOperand(3).isImm() && "Invalid subreg_to_reg");
unsigned DstReg = MI->getOperand(0).getReg();
unsigned InsReg = MI->getOperand(2).getReg();
assert(!MI->getOperand(2).getSubReg() && "SubIdx on physreg?");
unsigned SubIdx = MI->getOperand(3).getImm();
assert(SubIdx != 0 && "Invalid index for insert_subreg");
unsigned DstSubReg = TRI->getSubReg(DstReg, SubIdx);
assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
"Insert destination must be in a physical register");
assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
"Inserted value must be in a physical register");
DEBUG(dbgs() << "subreg: CONVERTING: " << *MI);
if (DstSubReg == InsReg) {
// No need to insert an identify copy instruction.
// Watch out for case like this:
// %RAX<def> = SUBREG_TO_REG 0, %EAX<kill>, 3
// We must leave %RAX live.
if (DstReg != InsReg) {
MI->setDesc(TII->get(TargetOpcode::KILL));
MI->RemoveOperand(3); // SubIdx
MI->RemoveOperand(1); // Imm
DEBUG(dbgs() << "subreg: replace by: " << *MI);
return true;
}
DEBUG(dbgs() << "subreg: eliminated!");
} else {
TII->copyPhysReg(*MBB, MI, MI->getDebugLoc(), DstSubReg, InsReg,
MI->getOperand(2).isKill());
// Transfer the kill/dead flags, if needed.
if (MI->getOperand(0).isDead())
TransferDeadFlag(MI, DstSubReg, TRI);
DEBUG({
MachineBasicBlock::iterator dMI = MI;
dbgs() << "subreg: " << *(--dMI);
});
}
DEBUG(dbgs() << '\n');
MBB->erase(MI);
return true;
}
bool LowerSubregsInstructionPass::LowerCopy(MachineInstr *MI) {
MachineOperand &DstMO = MI->getOperand(0);
MachineOperand &SrcMO = MI->getOperand(1);
if (SrcMO.getReg() == DstMO.getReg()) {
DEBUG(dbgs() << "identity copy: " << *MI);
// No need to insert an identity copy instruction, but replace with a KILL
// if liveness is changed.
if (DstMO.isDead() || SrcMO.isUndef() || MI->getNumOperands() > 2) {
// We must make sure the super-register gets killed. Replace the
// instruction with KILL.
MI->setDesc(TII->get(TargetOpcode::KILL));
DEBUG(dbgs() << "replaced by: " << *MI);
return true;
}
// Vanilla identity copy.
MI->eraseFromParent();
return true;
}
DEBUG(dbgs() << "real copy: " << *MI);
TII->copyPhysReg(*MI->getParent(), MI, MI->getDebugLoc(),
DstMO.getReg(), SrcMO.getReg(), SrcMO.isKill());
if (DstMO.isDead())
TransferDeadFlag(MI, DstMO.getReg(), TRI);
if (MI->getNumOperands() > 2)
TransferImplicitDefs(MI);
DEBUG({
MachineBasicBlock::iterator dMI = MI;
dbgs() << "replaced by: " << *(--dMI);
});
MI->eraseFromParent();
return true;
}
/// runOnMachineFunction - Reduce subregister inserts and extracts to register
/// copies.
///
bool LowerSubregsInstructionPass::runOnMachineFunction(MachineFunction &MF) {
DEBUG(dbgs() << "Machine Function\n"
<< "********** LOWERING SUBREG INSTRS **********\n"
<< "********** Function: "
<< MF.getFunction()->getName() << '\n');
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
bool MadeChange = false;
for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
mbbi != mbbe; ++mbbi) {
for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
mi != me;) {
MachineBasicBlock::iterator nmi = llvm::next(mi);
MachineInstr *MI = mi;
assert(!MI->isInsertSubreg() && "INSERT_SUBREG should no longer appear");
assert(MI->getOpcode() != TargetOpcode::EXTRACT_SUBREG &&
"EXTRACT_SUBREG should no longer appear");
if (MI->isSubregToReg()) {
MadeChange |= LowerSubregToReg(MI);
} else if (MI->isCopy()) {
MadeChange |= LowerCopy(MI);
}
mi = nmi;
}
}
return MadeChange;
}
|
