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 //
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 "examples.h"
28
29 #define __ masm->
30
GenerateCrc32(MacroAssembler * masm)31 void 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
runExample(const char * msg)68 void 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
main(void)95 int main(void) {
96 runExample("Hello World!");
97 runExample("do");
98 runExample("1");
99 runExample("");
100
101 return 0;
102 }
103 #endif // TEST_EXAMPLES
104