noop.isa revision 2706:d88c27f75121 
1// -*- mode:c++ -*-
2
3// Copyright (c) 2003-2006 The Regents of The University of Michigan
4// All rights reserved.
5//
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15// this software without specific prior written permission.
16//
17// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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28//
29// Authors: Korey Sewell
30
31////////////////////////////////////////////////////////////////////
32//
33// Nop
34//
35
36output header {{
37    /**
38     * Static instruction class for no-ops.  This is a leaf class.
39     */
40    class Nop : public MipsStaticInst
41    {
42        /// Disassembly of original instruction.
43        const std::string originalDisassembly;
44
45      public:
46        /// Constructor
47        Nop(const std::string _originalDisassembly, MachInst _machInst)
48            : MipsStaticInst("nop", _machInst, No_OpClass),
49              originalDisassembly(_originalDisassembly)
50        {
51            flags[IsNop] = true;
52        }
53
54        ~Nop() { }
55
56        std::string
57        generateDisassembly(Addr pc, const SymbolTable *symtab) const;
58
59        %(BasicExecDeclare)s
60    };
61}};
62
63output decoder {{
64    std::string Nop::generateDisassembly(Addr pc,
65                                         const SymbolTable *symtab) const
66    {
67        return csprintf("%-10s %s", "nop", originalDisassembly);
68    }
69
70    /// Helper function for decoding nops.  Substitute Nop object
71    /// for original inst passed in as arg (and delete latter).
72    inline
73    MipsStaticInst *
74    makeNop(MipsStaticInst *inst)
75    {
76        MipsStaticInst *nop = new Nop(inst->disassemble(0), inst->machInst);
77        delete inst;
78        return nop;
79    }
80}};
81
82output exec {{
83    Fault
84    Nop::execute(%(CPU_exec_context)s *, Trace::InstRecord *) const
85    {
86        return NoFault;
87    }
88}};
89
90// integer & FP operate instructions use RT as dest, so check for
91// RT == 0 to detect nops
92def template OperateNopCheckDecode {{
93 {
94     MipsStaticInst *i = new %(class_name)s(machInst);
95
96     //if (RD == 0) {
97     //  i = makeNop(i);
98     //}
99
100     return i;
101 }
102}};
103
104
105// Like BasicOperate format, but generates NOP if RC/FC == 31
106def format BasicOperateWithNopCheck(code, *opt_args) {{
107    iop = InstObjParams(name, Name, 'MipsStaticInst', CodeBlock(code),
108                        opt_args)
109    header_output = BasicDeclare.subst(iop)
110    decoder_output = BasicConstructor.subst(iop)
111    decode_block = OperateNopCheckDecode.subst(iop)
112    exec_output = BasicExecute.subst(iop)
113}};
114
115def format Nop() {{
116        decode_block = 'return new Nop(\"\",machInst);\n'
117}};
118
119