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//===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//
// This pass is used to make Pc relative loads of constants.
// For now, only Mips16 will use this. While it has the same name and
// uses many ideas from the LLVM ARM Constant Island Pass, it's not intended
// to reuse any of the code from the ARM version.
//
// Loading constants inline is expensive on Mips16 and it's in general better
// to place the constant nearby in code space and then it can be loaded with a
// simple 16 bit load instruction.
//
// The constants can be not just numbers but addresses of functions and labels.
// This can be particularly helpful in static relocation mode for embedded
// non linux targets.
//
//
#define DEBUG_TYPE "mips-constant-islands"
#include "Mips.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "MipsTargetMachine.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
namespace {
typedef MachineBasicBlock::iterator Iter;
typedef MachineBasicBlock::reverse_iterator ReverseIter;
class MipsConstantIslands : public MachineFunctionPass {
public:
static char ID;
MipsConstantIslands(TargetMachine &tm)
: MachineFunctionPass(ID), TM(tm),
IsPIC(TM.getRelocationModel() == Reloc::PIC_),
ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()) {}
virtual const char *getPassName() const {
return "Mips Constant Islands";
}
bool runOnMachineFunction(MachineFunction &F);
private:
const TargetMachine &TM;
bool IsPIC;
unsigned ABI;
};
char MipsConstantIslands::ID = 0;
} // end of anonymous namespace
/// createMipsLongBranchPass - Returns a pass that converts branches to long
/// branches.
FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) {
return new MipsConstantIslands(tm);
}
bool MipsConstantIslands::runOnMachineFunction(MachineFunction &F) {
// The intention is for this to be a mips16 only pass for now
// FIXME:
// if (!TM.getSubtarget<MipsSubtarget>().inMips16Mode())
// return false;
return false;
}
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