1// Copyright 2015, 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//
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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//
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25// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26
27#include "examples.h"
28
29#define __ masm->
30
31void GenerateCrc32(MacroAssembler* masm) {
32  // uint32_t crc32(const char *msg, size_t length)
33  // Argument location:
34  //   msg (pointer)    -> x0
35  //   length (integer) -> x1
36
37  // This example computes CRC32CB on an input array of a given size
38  // and returns the resulting checksum in w0.
39
40  Label loop, end;
41
42  // Move input array to temp register so we can re-use w0 as return register.
43  __ Mov(x2, x0);
44
45  // Initial remainder for the checksum. If length=0, then this value will be
46  // returned.
47  __ Mov(w0, 0xffffffff);
48
49  // Loop for iterating through the array, starting at msg[0].
50  __ Bind(&loop);
51
52  // If no more elements to process, then exit function.
53  __ Cbz(x1, &end);
54  __ Sub(x1, x1, 1);
55
56  // Compute checksum for msg[i].
57  __ Ldrb(w3, MemOperand(x2, 1, PostIndex));
58  __ Crc32b(w0, w0, w3);
59  __ B(&loop);
60
61  __ Bind(&end);
62
63  __ Ret();
64}
65
66#ifndef TEST_EXAMPLES
67
68void runExample(const char* msg) {
69  MacroAssembler masm;
70
71  // Generate the code for the example function.
72  Label func;
73  masm.Bind(&func);
74  GenerateCrc32(&masm);
75  masm.FinalizeCode();
76
77#ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
78  // Run example function in the simulator.
79  uintptr_t msg_addr = reinterpret_cast<uintptr_t>(msg);
80  size_t msg_size = strlen(msg);
81  Decoder decoder;
82  Simulator simulator(&decoder);
83  simulator.WriteXRegister(0, msg_addr);
84  simulator.WriteXRegister(1, msg_size);
85  simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&func));
86  printf("crc32(\"%s\")=0x%x\n", msg, simulator.ReadWRegister(0));
87#else
88  // Run example function natively.
89  printf("Not yet implemented.\n");
90  USE(msg);
91#endif  // VIXL_INCLUDE_SIMULATOR_AARCH64
92}
93
94
95int main(void) {
96  runExample("Hello World!");
97  runExample("do");
98  runExample("1");
99  runExample("");
100
101  return 0;
102}
103#endif  // TEST_EXAMPLES
104