xref: /aosp_15_r20/external/vixl/examples/aarch64/factorial.cc (revision f5c631da2f1efdd72b5fd1e20510e4042af13d77)

// Copyright 2014, VIXL authors
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#include "examples.h"

using namespace vixl;
using namespace vixl::aarch64;

#define __ masm->

void GenerateFactorial(MacroAssembler* masm) {
  // uint64_t factorial(uint64_t n)
  // Argument location:
  //   n -> x0

  Label loop, end;

  __ Mov(x1, x0);
  __ Mov(x0, 1);  // Use x0 as the accumulator.

  __ Cbz(x1, &end);  // Nothing to do if the input is null.

  __ Bind(&loop);
  __ Mul(x0, x0, x1);
  __ Sub(x1, x1, 1);
  __ Cbnz(x1, &loop);

  __ Bind(&end);
  // The return value is in x0.
  __ Ret();
}


#ifndef TEST_EXAMPLES
#ifdef VIXL_INCLUDE_SIMULATOR_AARCH64
int main(void) {
  MacroAssembler masm;
  Decoder decoder;
  Simulator simulator(&decoder);

  // Generate the code for the example function.
  Label factorial;
  masm.Bind(&factorial);
  GenerateFactorial(&masm);
  masm.FinalizeCode();

  // Run the example function.
  uint64_t input_val = 16;
  simulator.WriteXRegister(0, input_val);
  simulator.RunFrom(masm.GetLabelAddress<Instruction*>(&factorial));
  printf("factorial(%" PRIu64 ") = %" PRId64 "\n",
         input_val,
         simulator.ReadXRegister(0));

  return 0;
}
#else
// Without the simulator there is nothing to test.
int main(void) { return 0; }
#endif  // VIXL_INCLUDE_SIMULATOR_AARCH64
#endif  // TEST_EXAMPLES