tests/tcg/mips/mipsr5900/div1.c

   1 /*
   2  * Test R5900-specific DIV1.
   3  */
   4
   5 #include <stdio.h>
   6 #include <inttypes.h>
   7 #include <assert.h>
   8
   9 struct quotient_remainder { int32_t quotient, remainder; };
  10
  11 static struct quotient_remainder div1(int32_t rs, int32_t rt)
  12 {
  13     int32_t lo, hi;
  14
  15     __asm__ __volatile__ (
  16             "    div1 $0, %2, %3\n"
  17             "    mflo1 %0\n"
  18             "    mfhi1 %1\n"
  19             : "=r" (lo), "=r" (hi)
  20             : "r" (rs), "r" (rt));
  21
  22     assert(rs / rt == lo);
  23     assert(rs % rt == hi);
  24
  25     return (struct quotient_remainder) { .quotient = lo, .remainder = hi };
  26 }
  27
  28 static void verify_div1(int32_t rs, int32_t rt,
  29                         int32_t expected_quotient,
  30                         int32_t expected_remainder)
  31 {
  32     struct quotient_remainder qr = div1(rs, rt);
  33
  34     assert(qr.quotient == expected_quotient);
  35     assert(qr.remainder == expected_remainder);
  36 }
  37
  38 static void verify_div1_negations(int32_t rs, int32_t rt,
  39                                   int32_t expected_quotient,
  40                                   int32_t expected_remainder)
  41 {
  42     verify_div1(rs, rt, expected_quotient, expected_remainder);
  43     verify_div1(rs, -rt, -expected_quotient, expected_remainder);
  44     verify_div1(-rs, rt, -expected_quotient, -expected_remainder);
  45     verify_div1(-rs, -rt, expected_quotient, -expected_remainder);
  46 }
  47
  48 int main()
  49 {
  50     verify_div1_negations(0, 1, 0, 0);
  51     verify_div1_negations(1, 1, 1, 0);
  52     verify_div1_negations(1, 2, 0, 1);
  53     verify_div1_negations(17, 19, 0, 17);
  54     verify_div1_negations(19, 17, 1, 2);
  55     verify_div1_negations(77773, 101, 770, 3);
  56
  57     verify_div1(-0x80000000,  1, -0x80000000, 0);
  58
  59     /*
  60      * Supplementary explanation from the Toshiba TX System RISC TX79 Core
  61      * Architecture manual, A-38 and B-7, https://wiki.qemu.org/File:C790.pdf
  62      *
  63      * Normally, when 0x80000000 (-2147483648) the signed minimum value is
  64      * divided by 0xFFFFFFFF (-1), the operation will result in an overflow.
  65      * However, in this instruction an overflow exception doesn't occur and
  66      * the result will be as follows:
  67      *
  68      * Quotient is 0x80000000 (-2147483648), and remainder is 0x00000000 (0).
  69      */
  70     verify_div1(-0x80000000, -1, -0x80000000, 0);
  71
  72     return 0;
  73 }