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      1 // Copyright 2014, 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 
     31 void GenerateFactorial(MacroAssembler* masm) {
     32   // uint64_t factorial(uint64_t n)
     33   // Argument location:
     34   //   n -> x0
     35 
     36   Label loop, end;
     37 
     38   __ Mov(x1, x0);
     39   __ Mov(x0, 1);  // Use x0 as the accumulator.
     40 
     41   __ Cbz(x1, &end);  // Nothing to do if the input is null.
     42 
     43   __ Bind(&loop);
     44   __ Mul(x0, x0, x1);
     45   __ Sub(x1, x1, 1);
     46   __ Cbnz(x1, &loop);
     47 
     48   __ Bind(&end);
     49   // The return value is in x0.
     50   __ Ret();
     51 }
     52 
     53 
     54 #ifndef TEST_EXAMPLES
     55 #ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
     56 int main(void) {
     57   MacroAssembler masm;
     58   Decoder decoder;
     59   Simulator simulator(&decoder);
     60 
     61   // Generate the code for the example function.
     62   Label factorial;
     63   masm.Bind(&factorial);
     64   GenerateFactorial(&masm);
     65   masm.FinalizeCode();
     66 
     67   // Run the example function.
     68   uint64_t input_val = 16;
     69   simulator.WriteXRegister(0, input_val);
     70   simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&factorial));
     71   printf("factorial(%" PRIu64 ") = %" PRId64 "\n",
     72          input_val,
     73          simulator.ReadXRegister(0));
     74 
     75   return 0;
     76 }
     77 #else
     78 // Without the simulator there is nothing to test.
     79 int main(void) { return 0; }
     80 #endif  // VIXL_INCLUDE_SIMULATOR_AARCH64
     81 #endif  // TEST_EXAMPLES
     82