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     26 
     27 #include "examples.h"
     28 
     29 // Macro to compute the number of elements in a vector.
     30 #define ARRAY_SIZE(Array) (sizeof(Array) / sizeof((Array)[0]))
     31 #define BUF_SIZE (4096)
     32 #define __ masm->
     33 
     34 /*
     35  * This example adds two vectors with 1-byte elements using NEON instructions,
     36  * and returns the results in the first vector.
     37  */
     38 void GenerateAdd2Vectors(MacroAssembler* masm) {
     39   // void add2_vectors(uint8_t *vec*, const uint8_t *vecB, unsigned size)
     40   // Argument locations:
     41   //    vecA (pointer) -> x0
     42   //    vecB (pointer) -> x1
     43   //    size (integer) -> w2
     44   // Result returned in vecA.
     45 
     46   Label loop16, loopr, end;
     47 
     48   // Loop to add vector elements in 16-byte chunks.
     49   __ Bind(&loop16);
     50 
     51   // Handle vectors smaller than 16-bytes in the remainder loop.
     52   __ Cmp(w2, 16);
     53   __ B(lo, &loopr);
     54   __ Sub(w2, w2, 16);
     55 
     56   // Add vectors in 16-byte chunks.
     57   __ Ld1(v0.V16B(), MemOperand(x0));
     58   __ Ld1(v1.V16B(), MemOperand(x1, 16, PostIndex));
     59   __ Add(v0.V16B(), v0.V16B(), v1.V16B());
     60   __ St1(v0.V16B(), MemOperand(x0, 16, PostIndex));
     61 
     62   __ B(&loop16);
     63 
     64   // Loop to add the remaining vector elements.
     65   __ Bind(&loopr);
     66 
     67   // If there are no more vector elements to process, then exit.
     68   __ Cbz(w2, &end);
     69   __ Sub(w2, w2, 1);
     70 
     71   // Add remaining vector elements in 1-byte chunks.
     72   __ Ldrb(w5, MemOperand(x0));
     73   __ Ldrb(w6, MemOperand(x1, 1, PostIndex));
     74   __ Add(w5, w5, w6);
     75   __ Strb(w5, MemOperand(x0, 1, PostIndex));
     76 
     77   __ B(&loopr);
     78 
     79   __ Bind(&end);
     80 
     81   __ Ret();
     82 }
     83 
     84 
     85 void PrintVector(const uint8_t *vec, unsigned num) {
     86   unsigned i;
     87   printf("( ");
     88   if (num > 0) {
     89     for (i = 0; i < num - 1; ++i) {
     90       printf("%d, ", vec[i]);
     91     }
     92     printf("%d", vec[i]);
     93   }
     94   printf(" )\n");
     95 }
     96 
     97 
     98 #ifndef TEST_EXAMPLES
     99 int main(void) {
    100   // Create and initialize the assembler.
    101   byte assm_buf[BUF_SIZE];
    102   MacroAssembler masm(assm_buf, BUF_SIZE);
    103 
    104   // Generate native code for the example function.
    105   Label add2_vectors;
    106   masm.Bind(&add2_vectors);
    107   GenerateAdd2Vectors(&masm);
    108   masm.FinalizeCode();
    109 
    110   // Initialize input data for the example function.
    111   uint8_t vecA[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
    112                     0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
    113                     16, 17, 18, 19, 20};
    114   uint8_t vecB[] = {16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
    115                     30, 31,
    116                     16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
    117                     30, 31,
    118                     32, 33, 34, 35, 36};
    119   uint8_t vecC[ARRAY_SIZE(vecA)];
    120 
    121   // Check whether the number of elements in both vectors match.
    122   assert(ARRAY_SIZE(vecA) == ARRAY_SIZE(vecB));
    123 
    124   // Compute the result in C.
    125   for (unsigned i = 0; i < ARRAY_SIZE(vecA); i++) {
    126     vecC[i] = vecA[i] + vecB[i];
    127   }
    128 
    129 #ifdef USE_SIMULATOR
    130   uintptr_t vecA_addr = reinterpret_cast<uintptr_t>(vecA);
    131   uintptr_t vecB_addr = reinterpret_cast<uintptr_t>(vecB);
    132 
    133   // Configure register environment in the simulator.
    134   Decoder decoder;
    135   Simulator simulator(&decoder);
    136   simulator.set_xreg(0, vecA_addr);
    137   simulator.set_xreg(1, vecB_addr);
    138   simulator.set_xreg(2, ARRAY_SIZE(vecA));
    139   PrintVector(vecA, ARRAY_SIZE(vecA));
    140   printf(" +\n");
    141   PrintVector(vecB, ARRAY_SIZE(vecB));
    142 
    143   // Run the example function in the simulator.
    144   simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&add2_vectors));
    145   printf(" =\n");
    146   PrintVector(vecA, ARRAY_SIZE(vecA));
    147 #else
    148   // Placeholder to run test natively.
    149   printf("Running tests natively is not supported yet.\n");
    150   return 0;
    151 #endif  // USE_SIMULATOR
    152   // Check that the computed value in NEON matches the C version.
    153   for (unsigned i = 0; i < ARRAY_SIZE(vecA); i++) {
    154     assert(vecC[i] == vecA[i]);
    155   }
    156 
    157   return 0;
    158 }
    159 #endif  // TEST_EXAMPLES
    160