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
25using namespace llvm;
26
27namespace {
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
46bool 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.
91FunctionPass *llvm::createMipsEmitGPRestorePass(MipsTargetMachine &tm) {
92  return new Inserter(tm);
93}
94
95