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//===-- MipsEmitGPRestore.cpp - Emit GP restore instruction----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass emits instructions that restore $gp right
// after jalr instructions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "emit-gp-restore"
#include "Mips.h"
#include "MipsTargetMachine.h"
#include "MipsMachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
namespace {
struct Inserter : public MachineFunctionPass {
TargetMachine &TM;
const TargetInstrInfo *TII;
static char ID;
Inserter(TargetMachine &tm)
: MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()) { }
virtual const char *getPassName() const {
return "Mips Emit GP Restore";
}
bool runOnMachineFunction(MachineFunction &F);
};
char Inserter::ID = 0;
} // end of anonymous namespace
bool Inserter::runOnMachineFunction(MachineFunction &F) {
if (TM.getRelocationModel() != Reloc::PIC_)
return false;
bool Changed = false;
int FI = F.getInfo<MipsFunctionInfo>()->getGPFI();
for (MachineFunction::iterator MFI = F.begin(), MFE = F.end();
MFI != MFE; ++MFI) {
MachineBasicBlock& MBB = *MFI;
MachineBasicBlock::iterator I = MFI->begin();
// If MBB is a landing pad, insert instruction that restores $gp after
// EH_LABEL.
if (MBB.isLandingPad()) {
// Find EH_LABEL first.
for (; I->getOpcode() != TargetOpcode::EH_LABEL; ++I) ;
// Insert lw.
++I;
DebugLoc dl = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
BuildMI(MBB, I, dl, TII->get(Mips::LW), Mips::GP).addImm(0)
.addFrameIndex(FI);
Changed = true;
}
while (I != MFI->end()) {
if (I->getOpcode() != Mips::JALR) {
++I;
continue;
}
DebugLoc dl = I->getDebugLoc();
// emit lw $gp, ($gp save slot on stack) after jalr
BuildMI(MBB, ++I, dl, TII->get(Mips::LW), Mips::GP).addImm(0)
.addFrameIndex(FI);
Changed = true;
}
}
return Changed;
}
/// createMipsEmitGPRestorePass - Returns a pass that emits instructions that
/// restores $gp clobbered by jalr instructions.
FunctionPass *llvm::createMipsEmitGPRestorePass(MipsTargetMachine &tm) {
return new Inserter(tm);
}
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