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/*

   Test integer division

   Use a software division algorithm to perform division and compare against

   the hardware calculated results

   TODO: Check the signed division software calculation stuff is 100% correct!

   Julius Baxter, julius@opencores.org

*/

#include "cpu-utils.h"

#include "printf.h"

static int sdiv_errors, udiv_errors;

#define VERBOSE_TESTS 0

// Make this bigger when running on FPGA target. For simulation it's enough.

#define NUM_TESTS 2000

int

or1k_div(int dividend, int divisor)

{

  int result;

  asm ("l.div\t%0,%1,%2" : "=r" (result) : "r" (dividend), "r" (divisor));

  return result;

}

unsigned int

or1k_divu(unsigned int dividend, unsigned int divisor)

{

  int result;

  asm ("l.divu\t%0,%1,%2" : "=r" (result) : "r" (dividend), "r" (divisor));

  return result;

}

void

check_div(int dividend, int divisor, int expected_result)

{

#if VERBOSE_TESTS

  printf("l.div 0x%.8x / 0x%.8x = (SW) 0x%.8x : ", dividend, divisor,

         expected_result);

#endif

  int result =  or1k_div(dividend, divisor);

  report(result);

  if ( result != expected_result)

    {

      printf("l.div 0x%.8x / 0x%.8x = (SW) 0x%.8x : ", dividend, divisor,

             expected_result);

      printf("(HW) 0x%.8x - MISMATCH\n",result);

      sdiv_errors++;

    }

#if VERBOSE_TESTS

  else

    printf("OK\n");

#endif

}

void

check_divu(unsigned int dividend, unsigned int divisor,

           unsigned int expected_result)

{

#if VERBOSE_TESTS

  printf("l.divu 0x%.8x / 0x%.8x = (SW) 0x%.8x : ", dividend, divisor,

         expected_result);

#endif

  unsigned int result =  or1k_divu(dividend, divisor);

  report(result);

  if ( result != expected_result)

    {

      printf("l.divu 0x%.8x / 0x%.8x = (SW) 0x%.8x : ", dividend, divisor,

             expected_result);

      printf("(HW) 0x%.8x - MISMATCH\n",result);

      udiv_errors++;

    }

#if VERBOSE_TESTS

  else

    printf("OK\n");

#endif

}

// Software implementation of division

unsigned int

div_soft(unsigned int n, unsigned int d)

{

  // unsigned 32-bit restoring divide algo:

  unsigned long long p, dd;

  long long p_signed;

  unsigned int q = 0;

  p = (unsigned long long) n;

  dd = (unsigned long long) d << 32;

  int i;

  for(i=31; i>-1; i--){

    p_signed = (2*p) - dd;

    if (p_signed>=0)

      {

        p = (2*p) - dd;

        q |= 1 << i;

      }

    else

      {

        p = p_signed + dd;

      }

  }

  return q;

}

int

main(void)

{

#ifdef _UART_H_

  uart_init(DEFAULT_UART);

#endif

  udiv_errors = 0;

  sdiv_errors = 0;

  int i;

  unsigned long n, d;

  unsigned long expected_result;

  i=0;

  while(i < NUM_TESTS)

    {

      n = rand();

      d = rand();

      report(0x10101010);

      while ( d >= n )

        d >>= (rand() & 0xff);

      if (n&0x80000000) // numerator is negative

        {

          // Calculate a value that's really smaller than the numerator

          while ( d >= ~(n-1) )

            d >>= (rand() & 0xff);

          if (!d) d = 1;

          // Processor thinks it's in 2's complement already, so we'll convert

          // from the interpreted 2's complement to unsigned for our calculation

          expected_result = div_soft(~(n-1), d);

          // Answer will be an unsigned +ve value, but of course it has to be

          // negative so convert back to 2's complment negative

          expected_result = ~expected_result + 1; // 2's complement

        }

      else

        expected_result = div_soft(n, d);

      /* Report things */

      report(n);

      report(d);

      report(expected_result);

      /* Signed divide */

      check_div(n, d, expected_result);

      /* Unsigned divide test */

      /* Ensure numerator's bit 31 is clear */

      n >>= 1;

      /* If divisor is > numerator, shift it by a random amount */

      while ( d >= n )

        d >>= (rand() & 0xff);

      if (!d) d = 1;

      expected_result = div_soft(n, d);

      /* Report things */

      report(n);

      report(d);

      report(expected_result);

      /* Unsigned divide */

      check_divu(n, d, expected_result);

      i++;

    }

  printf("Division check complete\n");

  printf("Unsigned:\t%d tests\t %d errors\n",

         NUM_TESTS, udiv_errors);

  printf("Signed:\t\t%d tests\t %d errors\n",

         NUM_TESTS, sdiv_errors);

  if ((udiv_errors > 0) || (sdiv_errors > 0))

    report(0xbaaaaaad);

  else

    report(0x8000000d);

  return 0;

}