http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21718
--- Comment #12 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> 2012-11-05 00:16:32 UTC --- (In reply to comment #11) > Really I'd consider this just a variant on bug 21718 (real.c rounding not > perfect). That would ideally be fixed by using MPFR for this in GCC ... > except that for any MPFR versions before 3.1.1p2, the bug I found with the > ternary value from mpfr_strtofr could cause problems for subnormal > results. Alternatively, you can write code based on MPFR without using the ternary value. The algorithm would be: 1. Round to the target precision. 2. If the result is in the subnormal range (this can be detected by looking at the exponent of the result), then deduce the "real" precision from the exponent, and recompute the result in this precision directly.
