1//===---------- PPCTLSDynamicCall.cpp - TLS Dynamic Call Fixup ------------===//
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 pass expands ADDItls{ld,gd}LADDR[32] machine instructions into
10// separate ADDItls[gd]L[32] and GETtlsADDR[32] instructions, both of
11// which define GPR3. A copy is added from GPR3 to the target virtual
12// register of the original instruction. The GETtlsADDR[32] is really
13// a call instruction, so its target register is constrained to be GPR3.
14// This is not true of ADDItls[gd]L[32], but there is a legacy linker
15// optimization bug that requires the target register of the addi of
16// a local- or general-dynamic TLS access sequence to be GPR3.
17//
18// This is done in a late pass so that TLS variable accesses can be
19// fully commoned by MachineCSE.
20//
21//===----------------------------------------------------------------------===//
22
23#include "PPC.h"
24#include "PPCInstrBuilder.h"
25#include "PPCInstrInfo.h"
26#include "PPCTargetMachine.h"
27#include "llvm/CodeGen/LiveIntervals.h"
28#include "llvm/CodeGen/MachineFrameInfo.h"
29#include "llvm/CodeGen/MachineFunctionPass.h"
30#include "llvm/CodeGen/MachineInstrBuilder.h"
31#include "llvm/InitializePasses.h"
32#include "llvm/Support/Debug.h"
33#include "llvm/Support/raw_ostream.h"
34
35using namespace llvm;
36
37#define DEBUG_TYPE "ppc-tls-dynamic-call"
38
39namespace {
40 struct PPCTLSDynamicCall : public MachineFunctionPass {
41 static char ID;
42 PPCTLSDynamicCall() : MachineFunctionPass(ID) {
43 initializePPCTLSDynamicCallPass(*PassRegistry::getPassRegistry());
44 }
45
46 const PPCInstrInfo *TII;
47
48protected:
49 bool processBlock(MachineBasicBlock &MBB) {
50 bool Changed = false;
51 bool NeedFence = true;
52 const PPCSubtarget &Subtarget =
53 MBB.getParent()->getSubtarget<PPCSubtarget>();
54 bool Is64Bit = Subtarget.isPPC64();
55 bool IsAIX = Subtarget.isAIXABI();
56 bool IsLargeModel =
57 Subtarget.getTargetMachine().getCodeModel() == CodeModel::Large;
58 bool IsPCREL = false;
59 MachineFunction *MF = MBB.getParent();
60 MachineRegisterInfo &RegInfo = MF->getRegInfo();
61
62 for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
63 I != IE;) {
64 MachineInstr &MI = *I;
65 IsPCREL = isPCREL(MI);
66 // There are a number of slight differences in code generation
67 // when we call .__get_tpointer (32-bit AIX TLS).
68 bool IsTLSTPRelMI = MI.getOpcode() == PPC::GETtlsTpointer32AIX;
69 bool IsTLSLDAIXMI = (MI.getOpcode() == PPC::TLSLDAIX8 ||
70 MI.getOpcode() == PPC::TLSLDAIX);
71
72 if (MI.getOpcode() != PPC::ADDItlsgdLADDR &&
73 MI.getOpcode() != PPC::ADDItlsldLADDR &&
74 MI.getOpcode() != PPC::ADDItlsgdLADDR32 &&
75 MI.getOpcode() != PPC::ADDItlsldLADDR32 &&
76 MI.getOpcode() != PPC::TLSGDAIX &&
77 MI.getOpcode() != PPC::TLSGDAIX8 && !IsTLSTPRelMI && !IsPCREL &&
78 !IsTLSLDAIXMI) {
79 // Although we create ADJCALLSTACKDOWN and ADJCALLSTACKUP
80 // as scheduling fences, we skip creating fences if we already
81 // have existing ADJCALLSTACKDOWN/UP to avoid nesting,
82 // which causes verification error with -verify-machineinstrs.
83 if (MI.getOpcode() == PPC::ADJCALLSTACKDOWN)
84 NeedFence = false;
85 else if (MI.getOpcode() == PPC::ADJCALLSTACKUP)
86 NeedFence = true;
87
88 ++I;
89 continue;
90 }
91
92 LLVM_DEBUG(dbgs() << "TLS Dynamic Call Fixup:\n " << MI);
93
94 Register OutReg = MI.getOperand(i: 0).getReg();
95 Register InReg = PPC::NoRegister;
96 Register GPR3 = Is64Bit ? PPC::X3 : PPC::R3;
97 Register GPR4 = Is64Bit ? PPC::X4 : PPC::R4;
98 if (!IsPCREL && !IsTLSTPRelMI)
99 InReg = MI.getOperand(i: 1).getReg();
100 DebugLoc DL = MI.getDebugLoc();
101
102 unsigned Opc1, Opc2;
103 switch (MI.getOpcode()) {
104 default:
105 llvm_unreachable("Opcode inconsistency error");
106 case PPC::ADDItlsgdLADDR:
107 Opc1 = PPC::ADDItlsgdL;
108 Opc2 = PPC::GETtlsADDR;
109 break;
110 case PPC::ADDItlsldLADDR:
111 Opc1 = PPC::ADDItlsldL;
112 Opc2 = PPC::GETtlsldADDR;
113 break;
114 case PPC::ADDItlsgdLADDR32:
115 Opc1 = PPC::ADDItlsgdL32;
116 Opc2 = PPC::GETtlsADDR32;
117 break;
118 case PPC::ADDItlsldLADDR32:
119 Opc1 = PPC::ADDItlsldL32;
120 Opc2 = PPC::GETtlsldADDR32;
121 break;
122 case PPC::TLSLDAIX:
123 // TLSLDAIX is expanded to one copy and GET_TLS_MOD, so we only set
124 // Opc2 here.
125 Opc2 = PPC::GETtlsMOD32AIX;
126 break;
127 case PPC::TLSLDAIX8:
128 // TLSLDAIX8 is expanded to one copy and GET_TLS_MOD, so we only set
129 // Opc2 here.
130 Opc2 = PPC::GETtlsMOD64AIX;
131 break;
132 case PPC::TLSGDAIX8:
133 // TLSGDAIX8 is expanded to two copies and GET_TLS_ADDR, so we only
134 // set Opc2 here.
135 Opc2 = PPC::GETtlsADDR64AIX;
136 break;
137 case PPC::TLSGDAIX:
138 // TLSGDAIX is expanded to two copies and GET_TLS_ADDR, so we only
139 // set Opc2 here.
140 Opc2 = PPC::GETtlsADDR32AIX;
141 break;
142 case PPC::GETtlsTpointer32AIX:
143 // GETtlsTpointer32AIX is expanded to a call to GET_TPOINTER on AIX
144 // 32-bit mode within PPCAsmPrinter. This instruction does not need
145 // to change, so Opc2 is set to the same instruction opcode.
146 Opc2 = PPC::GETtlsTpointer32AIX;
147 break;
148 case PPC::PADDI8pc:
149 assert(IsPCREL && "Expecting General/Local Dynamic PCRel");
150 Opc1 = PPC::PADDI8pc;
151 Opc2 = MI.getOperand(i: 2).getTargetFlags() ==
152 PPCII::MO_GOT_TLSGD_PCREL_FLAG
153 ? PPC::GETtlsADDRPCREL
154 : PPC::GETtlsldADDRPCREL;
155 }
156
157 // We create ADJCALLSTACKUP and ADJCALLSTACKDOWN around _tls_get_addr
158 // as scheduling fence to avoid it is scheduled before
159 // mflr in the prologue and the address in LR is clobbered (PR25839).
160 // We don't really need to save data to the stack - the clobbered
161 // registers are already saved when the SDNode (e.g. PPCaddiTlsgdLAddr)
162 // gets translated to the pseudo instruction (e.g. ADDItlsgdLADDR).
163 if (NeedFence) {
164 MBB.getParent()->getFrameInfo().setAdjustsStack(true);
165 BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKDOWN)).addImm(0)
166 .addImm(0);
167 }
168
169 if (IsAIX) {
170 if (IsTLSLDAIXMI) {
171 // The relative order between the node that loads the variable
172 // offset from the TOC, and the .__tls_get_mod node is being tuned
173 // here. It is better to put the variable offset TOC load after the
174 // call, since this node can use clobbers r4/r5.
175 // Search for the pattern of the two nodes that load from the TOC
176 // (either for the variable offset or for the module handle), and
177 // then move the variable offset TOC load right before the node that
178 // uses the OutReg of the .__tls_get_mod node.
179 unsigned LDTocOp =
180 Is64Bit ? (IsLargeModel ? PPC::LDtocL : PPC::LDtoc)
181 : (IsLargeModel ? PPC::LWZtocL : PPC::LWZtoc);
182 if (!RegInfo.use_empty(RegNo: OutReg)) {
183 std::set<MachineInstr *> Uses;
184 // Collect all instructions that use the OutReg.
185 for (MachineOperand &MO : RegInfo.use_operands(Reg: OutReg))
186 Uses.insert(x: MO.getParent());
187 // Find the first user (e.g.: lwax/stfdx) of the OutReg within the
188 // current BB.
189 MachineBasicBlock::iterator UseIter = MBB.begin();
190 for (MachineBasicBlock::iterator IE = MBB.end(); UseIter != IE;
191 ++UseIter)
192 if (Uses.count(x: &*UseIter))
193 break;
194
195 // Additional handling is required when UserIter (the first user
196 // of OutReg) is pointing to a valid node that loads from the TOC.
197 // Check the pattern and do the movement if the pattern matches.
198 if (UseIter != MBB.end()) {
199 // Collect all associated nodes that load from the TOC. Use
200 // hasOneDef() to guard against unexpected scenarios.
201 std::set<MachineInstr *> LoadFromTocs;
202 for (MachineOperand &MO : UseIter->operands())
203 if (MO.isReg() && MO.isUse()) {
204 Register MOReg = MO.getReg();
205 if (RegInfo.hasOneDef(RegNo: MOReg)) {
206 MachineInstr *Temp =
207 RegInfo.getOneDef(Reg: MOReg)->getParent();
208 // For the current TLSLDAIX node, get the corresponding
209 // node that loads from the TOC for the InReg. Otherwise,
210 // Temp probably pointed to the variable offset TOC load
211 // we would like to move.
212 if (Temp == &MI && RegInfo.hasOneDef(RegNo: InReg))
213 Temp = RegInfo.getOneDef(Reg: InReg)->getParent();
214 if (Temp->getOpcode() == LDTocOp)
215 LoadFromTocs.insert(x: Temp);
216 } else {
217 // FIXME: analyze this scenario if there is one.
218 LoadFromTocs.clear();
219 break;
220 }
221 }
222
223 // Check the two nodes that loaded from the TOC: one should be
224 // "_$TLSML", and the other will be moved before the node that
225 // uses the OutReg of the .__tls_get_mod node.
226 if (LoadFromTocs.size() == 2) {
227 MachineBasicBlock::iterator TLSMLIter = MBB.end();
228 MachineBasicBlock::iterator OffsetIter = MBB.end();
229 // Make sure the two nodes that loaded from the TOC are within
230 // the current BB, and that one of them is from the "_$TLSML"
231 // pseudo symbol, while the other is from the variable.
232 for (MachineBasicBlock::iterator I = MBB.begin(),
233 IE = MBB.end();
234 I != IE; ++I)
235 if (LoadFromTocs.count(x: &*I)) {
236 MachineOperand MO = I->getOperand(i: 1);
237 if (MO.isGlobal() && MO.getGlobal()->hasName() &&
238 MO.getGlobal()->getName() == "_$TLSML")
239 TLSMLIter = I;
240 else
241 OffsetIter = I;
242 }
243 // Perform the movement when the desired scenario has been
244 // identified, which should be when both of the iterators are
245 // valid.
246 if (TLSMLIter != MBB.end() && OffsetIter != MBB.end())
247 OffsetIter->moveBefore(MovePos: &*UseIter);
248 }
249 }
250 }
251 // The module-handle is copied into r3. The copy is followed by
252 // GETtlsMOD32AIX/GETtlsMOD64AIX.
253 BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), GPR3)
254 .addReg(InReg);
255 // The call to .__tls_get_mod.
256 BuildMI(MBB, I, DL, TII->get(Opc2), GPR3).addReg(GPR3);
257 } else if (!IsTLSTPRelMI) {
258 // The variable offset and region handle (for TLSGD) are copied in
259 // r4 and r3. The copies are followed by
260 // GETtlsADDR32AIX/GETtlsADDR64AIX.
261 BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), GPR4)
262 .addReg(MI.getOperand(i: 1).getReg());
263 BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), GPR3)
264 .addReg(MI.getOperand(i: 2).getReg());
265 BuildMI(MBB, I, DL, TII->get(Opc2), GPR3).addReg(GPR3).addReg(GPR4);
266 } else
267 // The opcode of GETtlsTpointer32AIX does not change, because later
268 // this instruction will be expanded into a call to .__get_tpointer,
269 // which will return the thread pointer into r3.
270 BuildMI(MBB, I, DL, TII->get(Opc2), GPR3);
271 } else {
272 MachineInstr *Addi;
273 if (IsPCREL) {
274 Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3).addImm(0);
275 } else {
276 // Expand into two ops built prior to the existing instruction.
277 assert(InReg != PPC::NoRegister && "Operand must be a register");
278 Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3).addReg(InReg);
279 }
280
281 Addi->addOperand(Op: MI.getOperand(i: 2));
282
283 MachineInstr *Call =
284 (BuildMI(MBB, I, DL, TII->get(Opc2), GPR3).addReg(GPR3));
285 if (IsPCREL)
286 Call->addOperand(Op: MI.getOperand(i: 2));
287 else
288 Call->addOperand(Op: MI.getOperand(i: 3));
289 }
290 if (NeedFence)
291 BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKUP)).addImm(0).addImm(0);
292
293 BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), OutReg)
294 .addReg(GPR3);
295
296 // Move past the original instruction and remove it.
297 ++I;
298 MI.removeFromParent();
299
300 Changed = true;
301 }
302
303 return Changed;
304 }
305
306public:
307 bool isPCREL(const MachineInstr &MI) {
308 return (MI.getOpcode() == PPC::PADDI8pc) &&
309 (MI.getOperand(2).getTargetFlags() ==
310 PPCII::MO_GOT_TLSGD_PCREL_FLAG ||
311 MI.getOperand(2).getTargetFlags() ==
312 PPCII::MO_GOT_TLSLD_PCREL_FLAG);
313 }
314
315 bool runOnMachineFunction(MachineFunction &MF) override {
316 TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo();
317
318 bool Changed = false;
319
320 for (MachineBasicBlock &B : llvm::make_early_inc_range(Range&: MF))
321 if (processBlock(MBB&: B))
322 Changed = true;
323
324 return Changed;
325 }
326
327 void getAnalysisUsage(AnalysisUsage &AU) const override {
328 AU.addRequired<LiveIntervals>();
329 AU.addRequired<SlotIndexes>();
330 MachineFunctionPass::getAnalysisUsage(AU);
331 }
332 };
333}
334
335INITIALIZE_PASS_BEGIN(PPCTLSDynamicCall, DEBUG_TYPE,
336 "PowerPC TLS Dynamic Call Fixup", false, false)
337INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
338INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
339INITIALIZE_PASS_END(PPCTLSDynamicCall, DEBUG_TYPE,
340 "PowerPC TLS Dynamic Call Fixup", false, false)
341
342char PPCTLSDynamicCall::ID = 0;
343FunctionPass*
344llvm::createPPCTLSDynamicCallPass() { return new PPCTLSDynamicCall(); }
345

source code of llvm/lib/Target/PowerPC/PPCTLSDynamicCall.cpp