xref: /gem5/src/arch/mips/isa/formats/noop.isa

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

// Copyright (c) 2007 MIPS Technologies, Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met: redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer;
// redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution;
// neither the name of the copyright holders nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Authors: Korey 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 override;

        Fault execute(ExecContext *, Trace::InstRecord *) const override;
    };
}};

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(ExecContext *, 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'
}};