xref: /external/vixl/examples/factorial-rec.cc

// Copyright 2013, ARM Limited
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#include "examples.h"

#define BUF_SIZE (4096)
#define __ masm->

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

  Label entry, input_is_zero;

  __ Bind(&entry);
  // Check for the stopping condition: the input number is null.
  __ Cbz(x0, &input_is_zero);

  __ Mov(x1, x0);
  __ Sub(x0, x0, 1);
  __ Push(x1, lr);
  __ Bl(&entry);    // Recursive call factorial_rec(n - 1).
  __ Pop(lr, x1);
  __ Mul(x0, x0, x1);
  __ Ret();

  __ Bind(&input_is_zero);
  __ Mov(x0, 1);
  __ Ret();
}


#ifndef TEST_EXAMPLES
int main(void) {
  // Create and initialize the assembler and the simulator.
  byte assm_buf[BUF_SIZE];
  MacroAssembler masm(assm_buf, BUF_SIZE);
  Decoder decoder;
  Simulator simulator(&decoder);

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

  // Run the example function.
  uint64_t input_val = 16;
  simulator.set_xreg(0, input_val);
  simulator.RunFrom(factorial_rec.target());
  printf("factorial(%ld) = %ld\n", input_val, simulator.xreg(0));

  return 0;
}
#endif