1 //===-- MipsEmitGPRestore.cpp - Emit GP Restore Instruction ---------------===// 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 emits instructions that restore $gp right 11 // after jalr instructions. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #define DEBUG_TYPE "emit-gp-restore" 16 17 #include "Mips.h" 18 #include "MipsTargetMachine.h" 19 #include "MipsMachineFunction.h" 20 #include "llvm/CodeGen/MachineFunctionPass.h" 21 #include "llvm/CodeGen/MachineInstrBuilder.h" 22 #include "llvm/Target/TargetInstrInfo.h" 23 #include "llvm/ADT/Statistic.h" 24 25 using namespace llvm; 26 27 namespace { 28 struct Inserter : public MachineFunctionPass { 29 30 TargetMachine &TM; 31 const TargetInstrInfo *TII; 32 33 static char ID; 34 Inserter(TargetMachine &tm) 35 : MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()) { } 36 37 virtual const char *getPassName() const { 38 return "Mips Emit GP Restore"; 39 } 40 41 bool runOnMachineFunction(MachineFunction &F); 42 }; 43 char Inserter::ID = 0; 44 } // end of anonymous namespace 45 46 bool Inserter::runOnMachineFunction(MachineFunction &F) { 47 MipsFunctionInfo *MipsFI = F.getInfo<MipsFunctionInfo>(); 48 49 if ((TM.getRelocationModel() != Reloc::PIC_) || 50 (!MipsFI->globalBaseRegFixed())) 51 return false; 52 53 bool Changed = false; 54 int FI = MipsFI->getGPFI(); 55 56 for (MachineFunction::iterator MFI = F.begin(), MFE = F.end(); 57 MFI != MFE; ++MFI) { 58 MachineBasicBlock& MBB = *MFI; 59 MachineBasicBlock::iterator I = MFI->begin(); 60 61 // If MBB is a landing pad, insert instruction that restores $gp after 62 // EH_LABEL. 63 if (MBB.isLandingPad()) { 64 // Find EH_LABEL first. 65 for (; I->getOpcode() != TargetOpcode::EH_LABEL; ++I) ; 66 67 // Insert lw. 68 ++I; 69 DebugLoc dl = I != MBB.end() ? I->getDebugLoc() : DebugLoc(); 70 BuildMI(MBB, I, dl, TII->get(Mips::LW), Mips::GP).addFrameIndex(FI) 71 .addImm(0); 72 Changed = true; 73 } 74 75 while (I != MFI->end()) { 76 if (I->getOpcode() != Mips::JALR) { 77 ++I; 78 continue; 79 } 80 81 DebugLoc dl = I->getDebugLoc(); 82 // emit lw $gp, ($gp save slot on stack) after jalr 83 BuildMI(MBB, ++I, dl, TII->get(Mips::LW), Mips::GP).addFrameIndex(FI) 84 .addImm(0); 85 Changed = true; 86 } 87 } 88 89 return Changed; 90 } 91 92 /// createMipsEmitGPRestorePass - Returns a pass that emits instructions that 93 /// restores $gp clobbered by jalr instructions. 94 FunctionPass *llvm::createMipsEmitGPRestorePass(MipsTargetMachine &tm) { 95 return new Inserter(tm); 96 } 97 98