1 // Copyright 2014, VIXL authors
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are met:
6 //
7 // * Redistributions of source code must retain the above copyright notice,
8 // this list of conditions and the following disclaimer.
9 // * Redistributions in binary form must reproduce the above copyright notice,
10 // this list of conditions and the following disclaimer in the documentation
11 // and/or other materials provided with the distribution.
12 // * Neither the name of ARM Limited nor the names of its contributors may be
13 // used to endorse or promote products derived from this software without
14 // specific prior written permission.
15 //
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
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18 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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21 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26
27 #include "non-const-visitor.h"
28 #include "examples.h"
29
30 using namespace vixl;
31 using namespace vixl::aarch64;
32
33 #define __ masm->
34
35
VisitAddSubShifted(const Instruction * instr)36 void SwitchAddSubRegisterSources::VisitAddSubShifted(const Instruction* instr) {
37 int rn = instr->GetRn();
38 int rm = instr->GetRm();
39 // Only non-const visitors are allowed to discard constness of the visited
40 // instruction.
41 Instruction* mutable_instr = MutableInstruction(instr);
42 Instr instr_bits = mutable_instr->GetInstructionBits();
43
44 // Switch the bitfields for the `rn` and `rm` registers.
45 instr_bits &= ~(Rn_mask | Rm_mask);
46 instr_bits |= (rn << Rm_offset) | (rm << Rn_offset);
47
48 // Rewrite the instruction.
49 mutable_instr->SetInstructionBits(instr_bits);
50 }
51
52
GenerateNonConstVisitorTestCode(MacroAssembler * masm)53 void GenerateNonConstVisitorTestCode(MacroAssembler* masm) {
54 // int64_t foo(int64_t a, int64_t b)
55 // Argument locations:
56 // a -> x0
57 // b -> x1
58 __ Sub(x0, x0, x1);
59 // The return value is in x0.
60 __ Ret();
61 }
62
63
RunNonConstVisitorTestGeneratedCode(const Instruction * start_instr)64 int64_t RunNonConstVisitorTestGeneratedCode(const Instruction* start_instr) {
65 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
66 Decoder simulator_decoder;
67 Simulator simulator(&simulator_decoder);
68
69 int64_t a = 5;
70 int64_t b = 2;
71 simulator.WriteXRegister(0, a);
72 simulator.WriteXRegister(1, b);
73 simulator.RunFrom(start_instr);
74 int64_t res = simulator.ReadXRegister(0);
75 printf("foo(%" PRId64 ", %" PRId64 ") = %" PRId64 "\n", a, b, res);
76
77 return res;
78 #else
79 // Without the simulator there is nothing to test.
80 USE(start_instr);
81 return 0;
82 #endif
83 }
84
85
86 #ifndef TEST_EXAMPLES
87 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
main(void)88 int main(void) {
89 MacroAssembler masm;
90
91 // Generate the code.
92 Label code_start, code_end;
93 masm.Bind(&code_start);
94 GenerateNonConstVisitorTestCode(&masm);
95 masm.Bind(&code_end);
96 masm.FinalizeCode();
97 Instruction* instr_start = masm.GetLabelAddress<Instruction*>(&code_start);
98 Instruction* instr_end = masm.GetLabelAddress<Instruction*>(&code_end);
99
100 // Run the code a first time.
101 RunNonConstVisitorTestGeneratedCode(instr_start);
102
103 // Instantiate a decoder, disassembler, and our custom modifying visitor.
104 Decoder decoder;
105 PrintDisassembler disasm(stdout);
106 SwitchAddSubRegisterSources modifying_visitor;
107
108 // Register visitors in such a way that when visiting instructions, the
109 // decoder will first disassemble the original instruction, modify it, and
110 // then disassemble the modified instruction.
111 decoder.AppendVisitor(&disasm);
112 decoder.AppendVisitor(&modifying_visitor);
113 decoder.AppendVisitor(&disasm);
114
115 // Iterate through the instructions.
116 Instruction* instr;
117 for (instr = instr_start; instr < instr_end; instr += kInstructionSize) {
118 printf("---\n");
119 decoder.Decode(instr);
120 }
121
122 // Run the modified code and observe the different output from before.
123 RunNonConstVisitorTestGeneratedCode(instr_start);
124
125 return 0;
126 }
127 #else
128 // Without the simulator there is nothing to test.
main(void)129 int main(void) { return 0; }
130 #endif // VIXL_INCLUDE_SIMULATOR_AARCH64
131 #endif // TEST_EXAMPLES
132
133
134 // This is only used by the testing code.
ModifyNonConstVisitorTestGeneratedCode(Instruction * start,Instruction * end)135 void ModifyNonConstVisitorTestGeneratedCode(Instruction* start,
136 Instruction* end) {
137 Decoder decoder;
138 SwitchAddSubRegisterSources modifying_visitor;
139 decoder.AppendVisitor(&modifying_visitor);
140
141 Instruction* instr;
142 for (instr = start; instr < end; instr += kInstructionSize) {
143 printf("---\n");
144 decoder.Decode(instr);
145 }
146 }
147