1 #include <cstdint>
2 
3 struct alignas(16) float80_raw {
4   uint64_t mantissa;
5   uint16_t sign_exp;
6 };
7 
8 int main() {
9   float80_raw st[] = {
10     {0x8000000000000000, 0x4000},  // +2.0
11     {0x3f00000000000000, 0x0000},  // 1.654785e-4932 (denormal)
12     {0x0000000000000000, 0x0000},  // +0
13     {0x0000000000000000, 0x8000},  // -0
14     {0x8000000000000000, 0x7fff},  // +inf
15     {0x8000000000000000, 0xffff},  // -inf
16     {0xc000000000000000, 0xffff},  // nan
17     // st7 will be freed to test tag word better
18     {0x0000000000000000, 0x0000},  // +0
19   };
20 
21   // unmask divide-by-zero exception
22   uint16_t cw = 0x037b;
23   // used as single-precision float
24   uint32_t zero = 0;
25 
26   asm volatile(
27     "finit\n\t"
28     "fldcw %1\n\t"
29     // load on stack in reverse order to make the result easier to read
30     "fldt 0x70(%0)\n\t"
31     "fldt 0x60(%0)\n\t"
32     "fldt 0x50(%0)\n\t"
33     "fldt 0x40(%0)\n\t"
34     "fldt 0x30(%0)\n\t"
35     "fldt 0x20(%0)\n\t"
36     "fldt 0x10(%0)\n\t"
37     "fldt 0x00(%0)\n\t"
38     // free st7
39     "ffree %%st(7)\n\t"
40     // this should trigger a divide-by-zero
41     "fdivs (%2)\n\t"
42     "int3\n\t"
43     :
44     : "a"(st), "m"(cw), "b"(&zero)
45     : "st"
46   );
47 
48   return 0;
49 }
50