67ff03dd57
arg to __kernel_rem_pio2() gives 53-bit (double) precision, not single precision and/or the array dimension like I thought. prec == 2 is used in e_rem_pio2.c for double precision although it is documented to be for 64-bit (extended) precision, and I just reduced it by 1 thinking that this would give the value suitable for 24-bit (float) precision. Reducing it 1 more to the documented value for float precision doesn't actually work (it gives errors of ~0.75 ulps in the reduced arg, but errors of much less than 0.5 ulps are needed; the bug seems to be in kernel_rem_pio2.c). Keep using a value 1 larger than the documented value but supply an array large enough hold the extra unused result from this. The bug can also be fixed quickly by increasing init_jk[0] in k_rem_pio2.c from 2 to 3. This gives behaviour identical to using prec == 1 except it doesn't create the extra result. It isn't clear how the precision bug affects higher precisions. 113-bit (quad) is the largest precision, so there is no way to use a large precision to fix it. |
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