I'm sorry for a wide angle shotgun approach, but I wanted to discuss with all of the stakeholders how to phase in IEEE 128-bit floating point to the PowerPC toolchain. For those of you who are not on the gcc@gcc.gnu.org mailing list, this thread will be archived at: https://gcc.gnu.org/ml/gcc/
What I'm going to do is break this into several followups that each cover one topic, so that it is easier to address issues without having to requote the whole article. What I want to do in the GCC 4.10 time frame is add the ability of users to use IEEE 128-bit extended precision support, with as minimal disruption as possible to existing code. It is unfortunate that we could not have squeezed the support in the PowerPC little endian support with Elf v2, so that we would not have backwards compatibility issues on that platform, but alas it did not happen. Before IEEE 128-bit can be fully implemented, we will need to modify the compiler, libgcc, glibc, the debugger, and possibly other tools as well. Because different teams work on different schedules, it will likely be some time before all of the pieces are in place. However, we likely will need to make sure the compiler piece is in place before work can start on the libraries and debuggers. In terms of user impact, I really don't know how many people are using long double, or want to use IEEE 128-bit floating point. I would hope that if a user program does not use long double, there is not a flag day where they have to move to a compiler/library combination for a feature they don't use. -- Michael Meissner, IBM IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA email: meiss...@linux.vnet.ibm.com, phone: +1 (978) 899-4797
