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
17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
20 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
23 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26
27 #include <regex>
28
29 #include "examples.h"
30 #include "non-const-visitor.h"
31
32 using namespace vixl;
33 using namespace vixl::aarch64;
34
35 #define __ masm->
36
37
Visit(Metadata * metadata,const Instruction * instr)38 void SwitchAddSubRegisterSources::Visit(Metadata* metadata,
39 const Instruction* instr) {
40 const std::string& form = (*metadata)["form"];
41
42 // Match the forms for 32/64-bit add/subtract with shift, with optional flag
43 // setting.
44 if (std::regex_match(form, // NOLINT: avoid clang-tidy-4.0 errors.
45 std::regex("(?:add|sub)s?_(?:32|64)_addsub_shift"))) {
46 int rn = instr->GetRn();
47 int rm = instr->GetRm();
48 // Only non-const visitors are allowed to discard constness of the visited
49 // instruction.
50 Instruction* mutable_instr = MutableInstruction(instr);
51 Instr instr_bits = mutable_instr->GetInstructionBits();
52
53 // Switch the bitfields for the `rn` and `rm` registers.
54 instr_bits &= ~(Rn_mask | Rm_mask);
55 instr_bits |= (rn << Rm_offset) | (rm << Rn_offset);
56
57 // Rewrite the instruction.
58 mutable_instr->SetInstructionBits(instr_bits);
59 }
60 }
61
62
GenerateNonConstVisitorTestCode(MacroAssembler * masm)63 void GenerateNonConstVisitorTestCode(MacroAssembler* masm) {
64 // int64_t foo(int64_t a, int64_t b)
65 // Argument locations:
66 // a -> x0
67 // b -> x1
68 __ Sub(x0, x0, x1);
69 // The return value is in x0.
70 __ Ret();
71 }
72
73
RunNonConstVisitorTestGeneratedCode(const Instruction * start_instr)74 int64_t RunNonConstVisitorTestGeneratedCode(const Instruction* start_instr) {
75 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
76 Decoder simulator_decoder;
77 Simulator simulator(&simulator_decoder);
78
79 int64_t a = 5;
80 int64_t b = 2;
81 simulator.WriteXRegister(0, a);
82 simulator.WriteXRegister(1, b);
83 simulator.RunFrom(start_instr);
84 int64_t res = simulator.ReadXRegister(0);
85 printf("foo(%" PRId64 ", %" PRId64 ") = %" PRId64 "\n", a, b, res);
86
87 return res;
88 #else
89 // Without the simulator there is nothing to test.
90 USE(start_instr);
91 return 0;
92 #endif
93 }
94
95
96 #ifndef TEST_EXAMPLES
97 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
main(void)98 int main(void) {
99 MacroAssembler masm;
100
101 // Generate the code.
102 Label code_start, code_end;
103 masm.Bind(&code_start);
104 GenerateNonConstVisitorTestCode(&masm);
105 masm.Bind(&code_end);
106 masm.FinalizeCode();
107 Instruction* instr_start = masm.GetLabelAddress<Instruction*>(&code_start);
108 Instruction* instr_end = masm.GetLabelAddress<Instruction*>(&code_end);
109
110 // Run the code a first time.
111 RunNonConstVisitorTestGeneratedCode(instr_start);
112
113 // Instantiate a decoder, disassembler, and our custom modifying visitor.
114 Decoder decoder;
115 PrintDisassembler disasm(stdout);
116 SwitchAddSubRegisterSources modifying_visitor;
117
118 // Register visitors in such a way that when visiting instructions, the
119 // decoder will first disassemble the original instruction, modify it, and
120 // then disassemble the modified instruction.
121 decoder.AppendVisitor(&disasm);
122 decoder.AppendVisitor(&modifying_visitor);
123 decoder.AppendVisitor(&disasm);
124
125 // Iterate through the instructions.
126 Instruction* instr;
127 for (instr = instr_start; instr < instr_end; instr += kInstructionSize) {
128 printf("---\n");
129 decoder.Decode(instr);
130 }
131
132 // Run the modified code and observe the different output from before.
133 RunNonConstVisitorTestGeneratedCode(instr_start);
134
135 return 0;
136 }
137 #else
138 // Without the simulator there is nothing to test.
main(void)139 int main(void) { return 0; }
140 #endif // VIXL_INCLUDE_SIMULATOR_AARCH64
141 #endif // TEST_EXAMPLES
142
143
144 // This is only used by the testing code.
ModifyNonConstVisitorTestGeneratedCode(Instruction * start,Instruction * end)145 void ModifyNonConstVisitorTestGeneratedCode(Instruction* start,
146 Instruction* end) {
147 Decoder decoder;
148 SwitchAddSubRegisterSources modifying_visitor;
149 decoder.AppendVisitor(&modifying_visitor);
150
151 Instruction* instr;
152 for (instr = start; instr < end; instr += kInstructionSize) {
153 printf("---\n");
154 decoder.Decode(instr);
155 }
156 }
157