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/MachineFunctionPass.h" 29 #include "llvm/CodeGen/MachineInstrBuilder.h" 30 #include "llvm/Support/Debug.h" 31 #include "llvm/Support/raw_ostream.h" 32 33 using namespace llvm; 34 35 #define DEBUG_TYPE "ppc-tls-dynamic-call" 36 37 namespace { 38 struct PPCTLSDynamicCall : public MachineFunctionPass { 39 static char ID; 40 PPCTLSDynamicCall() : MachineFunctionPass(ID) { 41 initializePPCTLSDynamicCallPass(*PassRegistry::getPassRegistry()); 42 } 43 44 const PPCInstrInfo *TII; 45 LiveIntervals *LIS; 46 47 protected: 48 bool processBlock(MachineBasicBlock &MBB) { 49 bool Changed = false; 50 bool NeedFence = true; 51 bool Is64Bit = MBB.getParent()->getSubtarget<PPCSubtarget>().isPPC64(); 52 53 for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end(); 54 I != IE;) { 55 MachineInstr &MI = *I; 56 57 if (MI.getOpcode() != PPC::ADDItlsgdLADDR && 58 MI.getOpcode() != PPC::ADDItlsldLADDR && 59 MI.getOpcode() != PPC::ADDItlsgdLADDR32 && 60 MI.getOpcode() != PPC::ADDItlsldLADDR32) { 61 62 // Although we create ADJCALLSTACKDOWN and ADJCALLSTACKUP 63 // as scheduling fences, we skip creating fences if we already 64 // have existing ADJCALLSTACKDOWN/UP to avoid nesting, 65 // which causes verification error with -verify-machineinstrs. 66 if (MI.getOpcode() == PPC::ADJCALLSTACKDOWN) 67 NeedFence = false; 68 else if (MI.getOpcode() == PPC::ADJCALLSTACKUP) 69 NeedFence = true; 70 71 ++I; 72 continue; 73 } 74 75 LLVM_DEBUG(dbgs() << "TLS Dynamic Call Fixup:\n " << MI); 76 77 Register OutReg = MI.getOperand(0).getReg(); 78 Register InReg = MI.getOperand(1).getReg(); 79 DebugLoc DL = MI.getDebugLoc(); 80 unsigned GPR3 = Is64Bit ? PPC::X3 : PPC::R3; 81 unsigned Opc1, Opc2; 82 const unsigned OrigRegs[] = {OutReg, InReg, GPR3}; 83 84 switch (MI.getOpcode()) { 85 default: 86 llvm_unreachable("Opcode inconsistency error"); 87 case PPC::ADDItlsgdLADDR: 88 Opc1 = PPC::ADDItlsgdL; 89 Opc2 = PPC::GETtlsADDR; 90 break; 91 case PPC::ADDItlsldLADDR: 92 Opc1 = PPC::ADDItlsldL; 93 Opc2 = PPC::GETtlsldADDR; 94 break; 95 case PPC::ADDItlsgdLADDR32: 96 Opc1 = PPC::ADDItlsgdL32; 97 Opc2 = PPC::GETtlsADDR32; 98 break; 99 case PPC::ADDItlsldLADDR32: 100 Opc1 = PPC::ADDItlsldL32; 101 Opc2 = PPC::GETtlsldADDR32; 102 break; 103 } 104 105 // We create ADJCALLSTACKUP and ADJCALLSTACKDOWN around _tls_get_addr 106 // as scheduling fence to avoid it is scheduled before 107 // mflr in the prologue and the address in LR is clobbered (PR25839). 108 // We don't really need to save data to the stack - the clobbered 109 // registers are already saved when the SDNode (e.g. PPCaddiTlsgdLAddr) 110 // gets translated to the pseudo instruction (e.g. ADDItlsgdLADDR). 111 if (NeedFence) 112 BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKDOWN)).addImm(0) 113 .addImm(0); 114 115 // Expand into two ops built prior to the existing instruction. 116 MachineInstr *Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3) 117 .addReg(InReg); 118 Addi->addOperand(MI.getOperand(2)); 119 120 // The ADDItls* instruction is the first instruction in the 121 // repair range. 122 MachineBasicBlock::iterator First = I; 123 --First; 124 125 MachineInstr *Call = (BuildMI(MBB, I, DL, TII->get(Opc2), GPR3) 126 .addReg(GPR3)); 127 Call->addOperand(MI.getOperand(3)); 128 129 if (NeedFence) 130 BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKUP)).addImm(0).addImm(0); 131 132 BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), OutReg) 133 .addReg(GPR3); 134 135 // The COPY is the last instruction in the repair range. 136 MachineBasicBlock::iterator Last = I; 137 --Last; 138 139 // Move past the original instruction and remove it. 140 ++I; 141 MI.removeFromParent(); 142 143 // Repair the live intervals. 144 LIS->repairIntervalsInRange(&MBB, First, Last, OrigRegs); 145 Changed = true; 146 } 147 148 return Changed; 149 } 150 151 public: 152 bool runOnMachineFunction(MachineFunction &MF) override { 153 TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo(); 154 LIS = &getAnalysis<LiveIntervals>(); 155 156 bool Changed = false; 157 158 for (MachineFunction::iterator I = MF.begin(); I != MF.end();) { 159 MachineBasicBlock &B = *I++; 160 if (processBlock(B)) 161 Changed = true; 162 } 163 164 return Changed; 165 } 166 167 void getAnalysisUsage(AnalysisUsage &AU) const override { 168 AU.addRequired<LiveIntervals>(); 169 AU.addPreserved<LiveIntervals>(); 170 AU.addRequired<SlotIndexes>(); 171 AU.addPreserved<SlotIndexes>(); 172 MachineFunctionPass::getAnalysisUsage(AU); 173 } 174 }; 175 } 176 177 INITIALIZE_PASS_BEGIN(PPCTLSDynamicCall, DEBUG_TYPE, 178 "PowerPC TLS Dynamic Call Fixup", false, false) 179 INITIALIZE_PASS_DEPENDENCY(LiveIntervals) 180 INITIALIZE_PASS_DEPENDENCY(SlotIndexes) 181 INITIALIZE_PASS_END(PPCTLSDynamicCall, DEBUG_TYPE, 182 "PowerPC TLS Dynamic Call Fixup", false, false) 183 184 char PPCTLSDynamicCall::ID = 0; 185 FunctionPass* 186 llvm::createPPCTLSDynamicCallPass() { return new PPCTLSDynamicCall(); } 187