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 //
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
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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
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15 //
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
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25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26
27 #include "examples.h"
28
29 using namespace vixl;
30 using namespace vixl::aarch32;
31
32 #define __ masm->
33
GenerateApproximatePi(MacroAssembler * masm)34 void GenerateApproximatePi(MacroAssembler* masm) {
35 // double ApproximatePi(uint32_t iterations)
36 // Very rough approximation of pi
37 // pi/4 = 1 - 1/3 + 1/5 - 1/7 + ... + (-1)^n / (2n + 1)
38 __ Cmp(r0, 0);
39 __ Bx(eq, lr);
40 __ Vpush(Untyped64, DRegisterList(d8, 8));
41 __ Vldr(d0, 1.0);
42 __ Vldr(d1, 3.0);
43 __ Vldr(d2, 5.0);
44 __ Vldr(d3, 7.0);
45
46
47 __ Vmov(d4, 8.0);
48 __ Vmov(d5, 1.0);
49
50 __ Vmov(I64, d10, 0); // d10 = 0.0;
51 __ Vmov(I64, d11, 0); // d11 = 0.0;
52 __ Vmov(I64, d12, 0); // d12 = 0.0;
53 __ Vmov(I64, d13, 0); // d13 = 0.0
54
55 Label loop;
56 __ Bind(&loop);
57
58 __ Vdiv(F64, d6, d5, d0);
59 __ Vdiv(F64, d7, d5, d1);
60 __ Vdiv(F64, d8, d5, d2);
61 __ Vdiv(F64, d9, d5, d3);
62
63 __ Vadd(F64, d10, d10, d6);
64 __ Vadd(F64, d11, d11, d7);
65 __ Vadd(F64, d12, d12, d8);
66 __ Vadd(F64, d13, d13, d9);
67
68 __ Vadd(F64, d0, d0, d4);
69 __ Vadd(F64, d1, d1, d4);
70 __ Vadd(F64, d2, d2, d4);
71 __ Vadd(F64, d3, d3, d4);
72
73 __ Subs(r0, r0, 1);
74 __ B(ne, &loop);
75
76 __ Vmov(F64, d4, 4.0);
77 __ Vadd(F64, d10, d10, d12);
78 __ Vadd(F64, d11, d11, d13);
79 __ Vsub(F64, d10, d10, d11);
80 __ Vmul(F64, d0, d10, d4);
81 __ Vpop(Untyped64, DRegisterList(d8, 8));
82 __ Bx(lr);
83 }
84
85 #ifndef TEST_EXAMPLES
main()86 int main() {
87 MacroAssembler masm;
88 // Generate the code for the example function.
89 Label pi_approx;
90 masm.Bind(&pi_approx);
91 GenerateApproximatePi(&masm);
92 masm.FinalizeCode();
93 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH32
94 // There is no simulator defined for VIXL AArch32.
95 printf("This example cannot be simulated\n");
96 #else
97 byte* code = masm.GetBuffer()->GetStartAddress<byte*>();
98 uint32_t code_size = masm.GetSizeOfCodeGenerated();
99 ExecutableMemory memory(code, code_size);
100 // Run the example function.
101 double (*pi_function)(uint32_t) =
102 memory.GetEntryPoint<double (*)(uint32_t)>(pi_approx,
103 masm.GetInstructionSetInUse());
104 uint32_t repeat = 10000000;
105 double output_value = (*pi_function)(repeat);
106 printf("native: pi_approx(%u) = %3.10f\n", repeat, output_value);
107 #endif
108 return 0;
109 }
110 #endif // TEST_EXAMPLES
111