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//
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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
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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 GenerateFactorialRec(MacroAssembler* masm) {
32  // uint64_t factorial_rec(uint64_t n)
33  // Argument location:
34  //   n -> x0
35
36  Label entry, input_is_zero;
37
38  __ Bind(&entry);
39  // Check for the stopping condition: the input number is null.
40  __ Cbz(x0, &input_is_zero);
41
42  __ Mov(x1, x0);
43  __ Sub(x0, x0, 1);
44  __ Push(x1, lr);
45  __ Bl(&entry);  // Recursive call factorial_rec(n - 1).
46  __ Pop(lr, x1);
47  __ Mul(x0, x0, x1);
48  __ Ret();
49
50  __ Bind(&input_is_zero);
51  __ Mov(x0, 1);
52  __ Ret();
53}
54
55
56#ifndef TEST_EXAMPLES
57#ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
58int main(void) {
59  MacroAssembler masm;
60  Decoder decoder;
61  Simulator simulator(&decoder);
62
63  // Generate the code for the example function.
64  Label factorial_rec;
65  masm.Bind(&factorial_rec);
66  GenerateFactorialRec(&masm);
67  masm.FinalizeCode();
68
69  // Run the example function.
70  uint64_t input_val = 16;
71  simulator.WriteXRegister(0, input_val);
72  simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&factorial_rec));
73  printf("factorial(%" PRIu64 ") = %" PRId64 "\n",
74         input_val,
75         simulator.ReadXRegister(0));
76
77  return 0;
78}
79#else
80// Without the simulator there is nothing to test.
81int main(void) { return 0; }
82#endif  // VIXL_INCLUDE_SIMULATOR_AARCH64
83#endif  // TEST_EXAMPLES
84