llvm-6502/lib/Target/Mips/MipsMCInstLower.h
Akira Hatanaka 648f00c2f0 Add an option to use a virtual register as the global base register instead of
reserving a physical register ($gp or $28) for that purpose.

This will completely eliminate loads that restore the value of $gp after every
function call, if the register allocator assigns a callee-saved register, or
eliminate unnecessary loads if it assigns a temporary register. 

example:

.cpload $25       // set $gp.
...
.cprestore 16     // store $gp to stack slot 16($sp).
...
jalr $25          // function call. clobbers $gp.
lw $gp, 16($sp)   // not emitted if callee-saved reg is chosen.
...
lw $2, 4($gp)
...
jalr $25          // function call.
lw $gp, 16($sp)   // not emitted if $gp is not live after this instruction.
...



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151402 91177308-0d34-0410-b5e6-96231b3b80d8
2012-02-24 22:34:47 +00:00

51 lines
1.7 KiB
C++

//===-- MipsMCInstLower.h - Lower MachineInstr to MCInst -------*- C++ -*--===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef MIPSMCINSTLOWER_H
#define MIPSMCINSTLOWER_H
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/Support/Compiler.h"
namespace llvm {
class MCAsmInfo;
class MCContext;
class MCInst;
class MCOperand;
class MCSymbol;
class MachineInstr;
class MachineFunction;
class Mangler;
class MipsAsmPrinter;
/// MipsMCInstLower - This class is used to lower an MachineInstr into an
// MCInst.
class LLVM_LIBRARY_VISIBILITY MipsMCInstLower {
typedef MachineOperand::MachineOperandType MachineOperandType;
MCContext &Ctx;
Mangler *Mang;
MipsAsmPrinter &AsmPrinter;
public:
MipsMCInstLower(Mangler *mang, const MachineFunction &MF,
MipsAsmPrinter &asmprinter);
void Lower(const MachineInstr *MI, MCInst &OutMI) const;
void LowerCPLOAD(const MachineInstr *MI, SmallVector<MCInst, 4>& MCInsts);
void LowerCPRESTORE(const MachineInstr *MI, SmallVector<MCInst, 4>& MCInsts);
void LowerUnalignedLoadStore(const MachineInstr *MI,
SmallVector<MCInst, 4>& MCInsts);
void LowerSETGP01(const MachineInstr *MI, SmallVector<MCInst, 4>& MCInsts);
private:
MCOperand LowerSymbolOperand(const MachineOperand &MO,
MachineOperandType MOTy, unsigned Offset) const;
MCOperand LowerOperand(const MachineOperand& MO, unsigned offset = 0) const;
};
}
#endif