Short version of http://dstress.kuehne.cn/run/a/asm_f2xm1_01.d

# int main(){
#     float f = -1.0f;
#
#     asm{
#         finit;
#         fld f;
#         f2xm1;
#         fst f;
#     }
#
#     assert(f<0);
#
#     f += 0.5f;
#
#     f = (f>0) ? f : -f;
#
#     assert(f < f.epsilon * 4); // ** A **
#
#     f = 1.0;
#
#     asm{
#         finit;
#         fld f;
#         f2xm1;
#         fst f;
#     }
#
#     assert(f>0); // ** B **
#
#     return 0;
# }

gdmd-0.17 -O a.d && ./a

The execution asserts in ** B **. If ** A ** is commented out the executable behaves as expected.

Thomas