1 // Copyright 2015, ARM Limited
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.
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10 // this list of conditions and the following disclaimer in the documentation
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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 BUF_SIZE (4096)
30 #define __ masm->
31
GenerateCrc32(MacroAssembler * masm)32 void GenerateCrc32(MacroAssembler* masm) {
33 // uint32_t crc32(const char *msg, size_t length)
34 // Argument location:
35 // msg (pointer) -> x0
36 // length (integer) -> x1
37
38 // This example computes CRC32CB on an input array of a given size
39 // and returns the resulting checksum in w0.
40
41 Label loop, end;
42
43 // Move input array to temp register so we can re-use w0 as return register.
44 __ Mov(x2, x0);
45
46 // Initial remainder for the checksum. If length=0, then this value will
47 // be returned.
48 __ Mov(w0, 0xffffffff);
49
50 // Loop for iterating through the array, starting at msg[0].
51 __ Bind(&loop);
52
53 // If no more elements to process, then exit function.
54 __ Cbz(x1, &end);
55 __ Sub(x1, x1, 1);
56
57 // Compute checksum for msg[i].
58 __ Ldrb(w3, MemOperand(x2, 1, PostIndex));
59 __ Crc32b(w0, w0, w3);
60 __ B(&loop);
61
62 __ Bind(&end);
63
64 __ Ret();
65 }
66
67 #ifndef TEST_EXAMPLES
68
runExample(const char * msg)69 void runExample(const char *msg) {
70 // Create and initialize the assembler and the simulator.
71 byte assm_buf[BUF_SIZE];
72 MacroAssembler masm(assm_buf, BUF_SIZE);
73
74 // Generate the code for the example function.
75 Label func;
76 masm.Bind(&func);
77 GenerateCrc32(&masm);
78 masm.FinalizeCode();
79
80 #ifdef USE_SIMULATOR
81 // Run example function in the simulator.
82 uintptr_t msg_addr = reinterpret_cast<uintptr_t>(msg);
83 size_t msg_size = strlen(msg);
84 Decoder decoder;
85 Simulator simulator(&decoder);
86 simulator.set_xreg(0, msg_addr);
87 simulator.set_xreg(1, msg_size);
88 simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&func));
89 printf("crc32(\"%s\")=0x%x\n", msg, simulator.wreg(0));
90 #else
91 // Run example function natively.
92 printf("Not yet implemented.\n");
93 USE(msg);
94 #endif // USE_SIMULATOR
95 }
96
97
main(void)98 int main(void) {
99 runExample("Hello World!");
100 runExample("do");
101 runExample("1");
102 runExample("");
103
104 return 0;
105 }
106 #endif // TEST_EXAMPLES
107