noop.isa revision 2686:f0d591379ac3 
1// -*- mode:c++ -*-
2
3////////////////////////////////////////////////////////////////////
4//
5// Nop
6//
7
8output header {{
9    /**
10     * Static instruction class for no-ops.  This is a leaf class.
11     */
12    class Nop : public MipsStaticInst
13    {
14        /// Disassembly of original instruction.
15        const std::string originalDisassembly;
16
17      public:
18        /// Constructor
19        Nop(const std::string _originalDisassembly, MachInst _machInst)
20            : MipsStaticInst("nop", _machInst, No_OpClass),
21              originalDisassembly(_originalDisassembly)
22        {
23            flags[IsNop] = true;
24        }
25
26        ~Nop() { }
27
28        std::string
29        generateDisassembly(Addr pc, const SymbolTable *symtab) const;
30
31        %(BasicExecDeclare)s
32    };
33}};
34
35output decoder {{
36    std::string Nop::generateDisassembly(Addr pc,
37                                         const SymbolTable *symtab) const
38    {
39        return csprintf("%-10s %s", "nop", originalDisassembly);
40    }
41
42    /// Helper function for decoding nops.  Substitute Nop object
43    /// for original inst passed in as arg (and delete latter).
44    inline
45    MipsStaticInst *
46    makeNop(MipsStaticInst *inst)
47    {
48        MipsStaticInst *nop = new Nop(inst->disassemble(0), inst->machInst);
49        delete inst;
50        return nop;
51    }
52}};
53
54output exec {{
55    Fault
56    Nop::execute(%(CPU_exec_context)s *, Trace::InstRecord *) const
57    {
58        return NoFault;
59    }
60}};
61
62// integer & FP operate instructions use RT as dest, so check for
63// RT == 0 to detect nops
64def template OperateNopCheckDecode {{
65 {
66     MipsStaticInst *i = new %(class_name)s(machInst);
67
68     //if (RD == 0) {
69     //  i = makeNop(i);
70     //}
71
72     return i;
73 }
74}};
75
76
77// Like BasicOperate format, but generates NOP if RC/FC == 31
78def format BasicOperateWithNopCheck(code, *opt_args) {{
79    iop = InstObjParams(name, Name, 'MipsStaticInst', CodeBlock(code),
80                        opt_args)
81    header_output = BasicDeclare.subst(iop)
82    decoder_output = BasicConstructor.subst(iop)
83    decode_block = OperateNopCheckDecode.subst(iop)
84    exec_output = BasicExecute.subst(iop)
85}};
86
87def format Nop() {{
88        decode_block = 'return new Nop(\"\",machInst);\n'
89}};
90
91