noop.isa

来自「M5,一个功能强大的多处理器系统模拟器.很多针对处理器架构,性能的研究都使用它作」· ISA 代码 · 共 146 行

// -*- mode:c++ -*-

// Copyright (c) 2007 MIPS Technologies, Inc.  All Rights Reserved

//  This software is part of the M5 simulator.

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//Authors: Korey L. Sewell

////////////////////////////////////////////////////////////////////
//
// Nop
//

output header {{
    /**
     * Static instruction class for no-ops.  This is a leaf class.
     */
    class Nop : public MipsStaticInst
    {
	/// Disassembly of original instruction.
	const std::string originalDisassembly;

      public:
	/// Constructor
	Nop(const std::string _originalDisassembly, MachInst _machInst)
	    : MipsStaticInst("nop", _machInst, No_OpClass),
	      originalDisassembly(_originalDisassembly)
	{
	    flags[IsNop] = true;
	}

	~Nop() { }

	std::string
	generateDisassembly(Addr pc, const SymbolTable *symtab) const;

	%(BasicExecDeclare)s
    };
}};

output decoder {{
    std::string Nop::generateDisassembly(Addr pc,
					 const SymbolTable *symtab) const
    {
	return csprintf("%-10s %s", "nop", originalDisassembly);
    }

    /// Helper function for decoding nops.  Substitute Nop object
    /// for original inst passed in as arg (and delete latter).
    inline
    MipsStaticInst *
    makeNop(MipsStaticInst *inst)
    {
	std::string nop_str = "(" + inst->disassemble(0) + ")";
	MipsStaticInst *nop = new Nop(nop_str, inst->machInst);
	delete inst;
	return nop;
    }
}};

output exec {{
    Fault
    Nop::execute(%(CPU_exec_context)s *, Trace::InstRecord *) const
    {
	return NoFault;
    }
}};

// Int & FP operate instructions use RD as dest, so check for
// RD == 0 to detect nops
def template RegNopCheckDecode {{
 {
     MipsStaticInst *i = new %(class_name)s(machInst);
     //if (RD == 0) {
	 //i = makeNop(i);
	 //}
     return i;
 }
}};

def template OperateNopCheckDecode {{
 {
     MipsStaticInst *i = new %(class_name)s(machInst);
     //if (RD == 0) {
     // i = makeNop(i);
     //}
     return i;
 }
}};

// IntImm & Memory  instructions use Rt as dest, so check for
// Rt == 0 to detect nops
def template ImmNopCheckDecode {{
 {
     MipsStaticInst *i = new %(class_name)s(machInst);
     //if (RT == 0) {
     // i = makeNop(i);
     // }
     return i;
 }
}};


// Like BasicOperate format, but generates NOP if RC/FC == 31
def format BasicOperateWithNopCheck(code, *opt_args) {{
    iop = InstObjParams(name, Name, 'MipsStaticInst', code,
			opt_args)
    header_output = BasicDeclare.subst(iop)
    decoder_output = BasicConstructor.subst(iop)
    decode_block = OperateNopCheckDecode.subst(iop)
    exec_output = BasicExecute.subst(iop)
}};

def format Nop() {{
	decode_block = 'return new Nop(\"\",machInst);\n'
}};