noop.isa revision 2750:1cca27adb880 
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        std::string nop_str = "(" + inst->disassemble(0) + ")";
49        MipsStaticInst *nop = new Nop(nop_str, inst->machInst);
50        delete inst;
51        return nop;
52    }
53}};
54
55output exec {{
56    Fault
57    Nop::execute(%(CPU_exec_context)s *, Trace::InstRecord *) const
58    {
59        return NoFault;
60    }
61}};
62
63// Int & FP operate instructions use RD as dest, so check for
64// RD == 0 to detect nops
65def template RegNopCheckDecode {{
66 {
67     MipsStaticInst *i = new %(class_name)s(machInst);
68     //if (RD == 0) {
69         //i = makeNop(i);
70         //}
71     return i;
72 }
73}};
74
75def template OperateNopCheckDecode {{
76 {
77     MipsStaticInst *i = new %(class_name)s(machInst);
78     //if (RD == 0) {
79     // i = makeNop(i);
80     //}
81     return i;
82 }
83}};
84
85// IntImm & Memory  instructions use Rt as dest, so check for
86// Rt == 0 to detect nops
87def template ImmNopCheckDecode {{
88 {
89     MipsStaticInst *i = new %(class_name)s(machInst);
90     //if (RT == 0) {
91     // i = makeNop(i);
92     // }
93     return i;
94 }
95}};
96
97
98// Like BasicOperate format, but generates NOP if RC/FC == 31
99def format BasicOperateWithNopCheck(code, *opt_args) {{
100    iop = InstObjParams(name, Name, 'MipsStaticInst', CodeBlock(code),
101                        opt_args)
102    header_output = BasicDeclare.subst(iop)
103    decoder_output = BasicConstructor.subst(iop)
104    decode_block = OperateNopCheckDecode.subst(iop)
105    exec_output = BasicExecute.subst(iop)
106}};
107
108def format Nop() {{
109        decode_block = 'return new Nop(\"\",machInst);\n'
110}};
111
112