1 // Copyright 2016, VIXL authors
2 // All rights reserved.
3 //
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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
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26
27 #include "examples.h"
28
29 #define __ masm->
30
GenerateApproximatePi(MacroAssembler * masm)31 void GenerateApproximatePi(MacroAssembler* masm) {
32 // double ApproximatePi(uint32_t iterations)
33 // Very rough approximation of pi
34 // pi/4 = 1 - 1/3 + 1/5 - 1/7 + ... + (-1)^n / (2n + 1)
35 __ Cmp(r0, 0);
36 __ Bx(eq, lr);
37 __ Vpush(Untyped64, DRegisterList(d8, 8));
38 __ Vldr(d0, 1.0);
39 __ Vldr(d1, 3.0);
40 __ Vldr(d2, 5.0);
41 __ Vldr(d3, 7.0);
42
43
44 __ Vmov(d4, 8.0);
45 __ Vmov(d5, 1.0);
46
47 __ Vmov(I64, d10, 0); // d10 = 0.0;
48 __ Vmov(I64, d11, 0); // d11 = 0.0;
49 __ Vmov(I64, d12, 0); // d12 = 0.0;
50 __ Vmov(I64, d13, 0); // d13 = 0.0
51
52 Label loop;
53 __ Bind(&loop);
54
55 __ Vdiv(F64, d6, d5, d0);
56 __ Vdiv(F64, d7, d5, d1);
57 __ Vdiv(F64, d8, d5, d2);
58 __ Vdiv(F64, d9, d5, d3);
59
60 __ Vadd(F64, d10, d10, d6);
61 __ Vadd(F64, d11, d11, d7);
62 __ Vadd(F64, d12, d12, d8);
63 __ Vadd(F64, d13, d13, d9);
64
65 __ Vadd(F64, d0, d0, d4);
66 __ Vadd(F64, d1, d1, d4);
67 __ Vadd(F64, d2, d2, d4);
68 __ Vadd(F64, d3, d3, d4);
69
70 __ Subs(r0, r0, 1);
71 __ B(ne, &loop);
72
73 __ Vmov(F64, d4, 4.0);
74 __ Vadd(F64, d10, d10, d12);
75 __ Vadd(F64, d11, d11, d13);
76 __ Vsub(F64, d10, d10, d11);
77 __ Vmul(F64, d0, d10, d4);
78 __ Vpop(Untyped64, DRegisterList(d8, 8));
79 __ Bx(lr);
80 }
81
82 #ifndef TEST_EXAMPLES
main()83 int main() {
84 MacroAssembler masm;
85 // Generate the code for the example function.
86 Label pi_approx;
87 masm.Bind(&pi_approx);
88 GenerateApproximatePi(&masm);
89 masm.FinalizeCode();
90 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH32
91 // There is no simulator defined for VIXL AArch32.
92 printf("This example cannot be simulated\n");
93 #else
94 byte* code = masm.GetBuffer()->GetStartAddress<byte*>();
95 uint32_t code_size = masm.GetSizeOfCodeGenerated();
96 ExecutableMemory memory(code, code_size);
97 // Run the example function.
98 double (*pi_function)(uint32_t) =
99 memory.GetEntryPoint<double (*)(uint32_t)>(pi_approx);
100 uint32_t repeat = 10000000;
101 double output_value = (*pi_function)(repeat);
102 printf("native: pi_approx(%u) = %3.10f\n", repeat, output_value);
103 #endif
104 return 0;
105 }
106 #endif // TEST_EXAMPLES
107