On 2023-04-20 13:57, Siddhesh Poyarekar wrote:
For bounds that aren't representable, one could get error bounds from libm-test-ulps data in glibc, although I reckon those won't be exhaustive. From a quick peek at the sin/cos data, the arc target seems to be among the worst performers at about 7ulps, although if you include the complex routines we get close to 13 ulps. The very worst imprecision among all math routines (that's gamma) is at 16 ulps for power in glibc tests, so maybe allowing about 25-30 ulps error in bounds might work across the board.
I was thinking about this a bit more and it seems like limiting ranges to targets that can generate sane results (i.e. error bounds within, say, 5-6 ulps) and for the rest, avoid emitting the ranges altogether. Emitting a bad range for all architectures seems like a net worse solution again.
Thanks, Sid
