lib/Target/Mips/MipsEmitGPRestore.cpp

   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   if (TM.getRelocationModel() != Reloc::PIC_)
  48     return false;
  49
  50   bool Changed = false;
  51   int FI =  F.getInfo<MipsFunctionInfo>()->getGPFI();
  52
  53   for (MachineFunction::iterator MFI = F.begin(), MFE = F.end();
  54        MFI != MFE; ++MFI) {
  55     MachineBasicBlock& MBB = *MFI;
  56     MachineBasicBlock::iterator I = MFI->begin();
  57
  58     // If MBB is a landing pad, insert instruction that restores $gp after
  59     // EH_LABEL.
  60     if (MBB.isLandingPad()) {
  61       // Find EH_LABEL first.
  62       for (; I->getOpcode() != TargetOpcode::EH_LABEL; ++I) ;
  63
  64       // Insert lw.
  65       ++I;
  66       DebugLoc dl = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
  67       BuildMI(MBB, I, dl, TII->get(Mips::LW), Mips::GP).addFrameIndex(FI)
  68                                                        .addImm(0);
  69       Changed = true;
  70     }
  71
  72     while (I != MFI->end()) {
  73       if (I->getOpcode() != Mips::JALR) {
  74         ++I;
  75         continue;
  76       }
  77
  78       DebugLoc dl = I->getDebugLoc();
  79       // emit lw $gp, ($gp save slot on stack) after jalr
  80       BuildMI(MBB, ++I, dl, TII->get(Mips::LW), Mips::GP).addFrameIndex(FI)
  81                                                          .addImm(0);
  82       Changed = true;
  83     }
  84   }
  85
  86   return Changed;
  87 }
  88
  89 /// createMipsEmitGPRestorePass - Returns a pass that emits instructions that
  90 /// restores $gp clobbered by jalr instructions.
  91 FunctionPass *llvm::createMipsEmitGPRestorePass(MipsTargetMachine &tm) {
  92   return new Inserter(tm);
  93 }
  94