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Date: Fri, 2 Nov 2018 13:32:55 -0400 From: David Edelsohn <dje.gcc@...il.com> To: musl@...ts.openwall.com Subject: Re: [PATCH] PPC64 IEEE128 bit FP support I don't believe that musl currently supports IBM double-double long double format, only IEEE 754 64 bit double precision as long double. IBM is working with other toolchains to support both the original double-double and the new 128 bit quad precision through compiler options, compiler macros, header definitions, and symbol compatibility in libraries. musl still would not support IBM double-double format. I don't know if it would be necessary for musl libc long double to be selectable for backward compatibility or one can implement a "flag day" where a musl libc release switches to only 128 bit quad precision long double. Thanks, David On Fri, Nov 2, 2018 at 12:13 PM Rich Felker <dalias@...c.org> wrote: > > On Fri, Oct 26, 2018 at 03:01:20PM +0200, Szabolcs Nagy wrote: > > * Markus Wichmann <nullplan@....net> [2018-10-26 06:28:29 +0200]: > > > Now you just need to look through all the maths code to find all the > > > places that need changing. __floatscan() comes to mind immediately. And > > > I don't know if any of the libm functions needs adjustment for this new > > > format. > > > > generic c code in musl should work for all supported > > floating-point formats, which includes ieee binary128 > > for long double. > > > > only float.h needs to be set up according to the abi. > > > > some long double math functions don't have high quality > > implementations for ieee binary128 format though. > > Yes. Assuming there aren't other problems revealed by my questions > about argument passing and ISA levels, I think the only blocking issue > here is naming the ABI. I forgot to mention but that should also > involve a gcc patch that we can put in mcm and eventually upstream. > > QoI issues for IEEE-quad-based [sub]archs can be improved later; > aarch64 and s390x are already affected IIRC. > > Rich
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