SystemZLDCleanup.cpp revision 309124
1//===-- SystemZLDCleanup.cpp - Clean up local-dynamic TLS accesses --------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This pass combines multiple accesses to local-dynamic TLS variables so that 11// the TLS base address for the module is only fetched once per execution path 12// through the function. 13// 14//===----------------------------------------------------------------------===// 15 16#include "SystemZTargetMachine.h" 17#include "SystemZMachineFunctionInfo.h" 18#include "llvm/CodeGen/MachineDominators.h" 19#include "llvm/CodeGen/MachineFunctionPass.h" 20#include "llvm/CodeGen/MachineInstrBuilder.h" 21#include "llvm/CodeGen/MachineRegisterInfo.h" 22#include "llvm/Target/TargetInstrInfo.h" 23#include "llvm/Target/TargetMachine.h" 24#include "llvm/Target/TargetRegisterInfo.h" 25 26using namespace llvm; 27 28namespace { 29 30class SystemZLDCleanup : public MachineFunctionPass { 31public: 32 static char ID; 33 SystemZLDCleanup(const SystemZTargetMachine &tm) 34 : MachineFunctionPass(ID), TII(nullptr), MF(nullptr) {} 35 36 const char *getPassName() const override { 37 return "SystemZ Local Dynamic TLS Access Clean-up"; 38 } 39 40 bool runOnMachineFunction(MachineFunction &MF) override; 41 void getAnalysisUsage(AnalysisUsage &AU) const override; 42 43private: 44 bool VisitNode(MachineDomTreeNode *Node, unsigned TLSBaseAddrReg); 45 MachineInstr *ReplaceTLSCall(MachineInstr *I, unsigned TLSBaseAddrReg); 46 MachineInstr *SetRegister(MachineInstr *I, unsigned *TLSBaseAddrReg); 47 48 const SystemZInstrInfo *TII; 49 MachineFunction *MF; 50}; 51 52char SystemZLDCleanup::ID = 0; 53 54} // end anonymous namespace 55 56FunctionPass *llvm::createSystemZLDCleanupPass(SystemZTargetMachine &TM) { 57 return new SystemZLDCleanup(TM); 58} 59 60void SystemZLDCleanup::getAnalysisUsage(AnalysisUsage &AU) const { 61 AU.setPreservesCFG(); 62 AU.addRequired<MachineDominatorTree>(); 63 MachineFunctionPass::getAnalysisUsage(AU); 64} 65 66bool SystemZLDCleanup::runOnMachineFunction(MachineFunction &F) { 67 if (skipFunction(*F.getFunction())) 68 return false; 69 70 TII = static_cast<const SystemZInstrInfo *>(F.getSubtarget().getInstrInfo()); 71 MF = &F; 72 73 SystemZMachineFunctionInfo* MFI = F.getInfo<SystemZMachineFunctionInfo>(); 74 if (MFI->getNumLocalDynamicTLSAccesses() < 2) { 75 // No point folding accesses if there isn't at least two. 76 return false; 77 } 78 79 MachineDominatorTree *DT = &getAnalysis<MachineDominatorTree>(); 80 return VisitNode(DT->getRootNode(), 0); 81} 82 83// Visit the dominator subtree rooted at Node in pre-order. 84// If TLSBaseAddrReg is non-null, then use that to replace any 85// TLS_LDCALL instructions. Otherwise, create the register 86// when the first such instruction is seen, and then use it 87// as we encounter more instructions. 88bool SystemZLDCleanup::VisitNode(MachineDomTreeNode *Node, 89 unsigned TLSBaseAddrReg) { 90 MachineBasicBlock *BB = Node->getBlock(); 91 bool Changed = false; 92 93 // Traverse the current block. 94 for (auto I = BB->begin(), E = BB->end(); I != E; ++I) { 95 switch (I->getOpcode()) { 96 case SystemZ::TLS_LDCALL: 97 if (TLSBaseAddrReg) 98 I = ReplaceTLSCall(&*I, TLSBaseAddrReg); 99 else 100 I = SetRegister(&*I, &TLSBaseAddrReg); 101 Changed = true; 102 break; 103 default: 104 break; 105 } 106 } 107 108 // Visit the children of this block in the dominator tree. 109 for (auto I = Node->begin(), E = Node->end(); I != E; ++I) 110 Changed |= VisitNode(*I, TLSBaseAddrReg); 111 112 return Changed; 113} 114 115// Replace the TLS_LDCALL instruction I with a copy from TLSBaseAddrReg, 116// returning the new instruction. 117MachineInstr *SystemZLDCleanup::ReplaceTLSCall(MachineInstr *I, 118 unsigned TLSBaseAddrReg) { 119 // Insert a Copy from TLSBaseAddrReg to R2. 120 MachineInstr *Copy = BuildMI(*I->getParent(), I, I->getDebugLoc(), 121 TII->get(TargetOpcode::COPY), SystemZ::R2D) 122 .addReg(TLSBaseAddrReg); 123 124 // Erase the TLS_LDCALL instruction. 125 I->eraseFromParent(); 126 127 return Copy; 128} 129 130// Create a virtal register in *TLSBaseAddrReg, and populate it by 131// inserting a copy instruction after I. Returns the new instruction. 132MachineInstr *SystemZLDCleanup::SetRegister(MachineInstr *I, 133 unsigned *TLSBaseAddrReg) { 134 // Create a virtual register for the TLS base address. 135 MachineRegisterInfo &RegInfo = MF->getRegInfo(); 136 *TLSBaseAddrReg = RegInfo.createVirtualRegister(&SystemZ::GR64BitRegClass); 137 138 // Insert a copy from R2 to TLSBaseAddrReg. 139 MachineInstr *Next = I->getNextNode(); 140 MachineInstr *Copy = BuildMI(*I->getParent(), Next, I->getDebugLoc(), 141 TII->get(TargetOpcode::COPY), *TLSBaseAddrReg) 142 .addReg(SystemZ::R2D); 143 144 return Copy; 145} 146 147