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;
Inserter__anone5c1457e0111::Inserter34 Inserter(TargetMachine &tm)
35 : MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()) { }
36
getPassName__anone5c1457e0111::Inserter37 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
runOnMachineFunction(MachineFunction & F)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.
createMipsEmitGPRestorePass(MipsTargetMachine & tm)91 FunctionPass *llvm::createMipsEmitGPRestorePass(MipsTargetMachine &tm) {
92 return new Inserter(tm);
93 }
94
95