On 7/2/20 9:27 AM, Joseph Myers wrote: > On Thu, 2 Jul 2020, Vineet Gupta via Libc-alpha wrote: > >> Now acos can come from 2 places depending on LIBM_SVID_COMPAT >> - math/w_acos_template.c <-- sets errno only > > This wrapper, unlike the compat one, always calls __ieee754_acos > (appropriately suffixed), relying on it to raise appropriate exceptions. > The implementation in sysdeps/ieee754/dbl-64/e_asin.c raises the exception > by doing an Inf / Inf computation. > > u.i[HIGH_HALF]=0x7ff00000; > v.i[HIGH_HALF]=0x7ff00000; > u.i[LOW_HALF]=0; > v.i[LOW_HALF]=0; > return u.x/v.x; > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95115
Aha. I almost forgot that this was upstream gcc-10 for ARC too (and problem doesn't happen with gcc-9). So my glibc updates didn't trigger this, phew ! > The right place to fix this is in GCC, to stop it constant-folding Inf / > Inf when flag_trapping_math. That should be a straightforward fix. > > It would also be reasonable to change the above code to just "return 0.0 / > 0.0;", as a simpler, more idiomatic way of returning a NaN with "invalid" > raised. (Any code constructing infinities / NaNs via bit patterns likely > predates built-in functions that can be used to represent such values > directly. Though the GCC bug means a literal replacement with "return > __builtin_inf () / __builtin_inf ();" wouldn't fix the present problem.) _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
