noop.isa revision 2632:1bb2f91485ea 
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#ifdef SS_COMPATIBLE_DISASSEMBLY
40        return originalDisassembly;
41#else
42        return csprintf("%-10s (%s)", "nop", originalDisassembly);
43#endif
44    }
45
46    /// Helper function for decoding nops.  Substitute Nop object
47    /// for original inst passed in as arg (and delete latter).
48    inline
49    MipsStaticInst *
50    makeNop(MipsStaticInst *inst)
51    {
52        MipsStaticInst *nop = new Nop(inst->disassemble(0), inst->machInst);
53        delete inst;
54        return nop;
55    }
56}};
57
58output exec {{
59    Fault
60    Nop::execute(%(CPU_exec_context)s *, Trace::InstRecord *) const
61    {
62        return NoFault;
63    }
64}};
65
66// integer & FP operate instructions use RT as dest, so check for
67// RT == 0 to detect nops
68def template OperateNopCheckDecode {{
69 {
70     MipsStaticInst *i = new %(class_name)s(machInst);
71
72     //if (RD == 0) {
73     //  i = makeNop(i);
74     //}
75
76     return i;
77 }
78}};
79
80
81// Like BasicOperate format, but generates NOP if RC/FC == 31
82def format BasicOperateWithNopCheck(code, *opt_args) {{
83    iop = InstObjParams(name, Name, 'MipsStaticInst', CodeBlock(code),
84                        opt_args)
85    header_output = BasicDeclare.subst(iop)
86    decoder_output = BasicConstructor.subst(iop)
87    decode_block = OperateNopCheckDecode.subst(iop)
88    exec_output = BasicExecute.subst(iop)
89}};
90
91def format Nop() {{
92        decode_block = 'return new Nop(\"sll r0,r0,0\",machInst);\n'
93}};
94
95