On Wed, 18 Mar 2020, Jim Wilson wrote: > > The new mnemonics have been supported by GAS for a little while now and > > the old ones have been retained, however this is still a change that > > breaks backwards compatibility. So I wonder if we shouldn't have an > > autoconf test included for this feature, and either resort to wiring GCC > > to keep using the old mnemonics or bail out at GCC compilation time if > > GAS is found not to handle the new ones. > > > > At the very least I think we ought to document the minimum version of > > binutils now required by GCC for RISC-V support. > > The new opcodes were added to gas in 2017-09-27, and I can't recommend > using any binutils or gcc release that predates 2018-01-01 because > they are all known to be buggy, or incompatible with the current ISA > definition. So I don't see any need for a configure test for this > change. Anyone missing the new instructions in gas has bigger > problems to worry about.
Fair enough. > As for the minimum binutils version, I would strongly recommend the > most recent one released before the gcc release that you are using, > though it is likely than anything back to 2018-01-01 would work, just > not as well. For me it's not an issue as I actively work on the toolchain and keep all checkouts close to the current tips of the respective master branches. However binary package maintainers or end users of the toolchain need to know the dependencies between component versions whether they want to build the pieces from sources or combine them from prebuilt packages. Our installation instructions state binutils 2.28 as the requirement for all the RISC-V targets, however the change for fmv.x.w/fmv.w.x instruction support was only added in the binutils 2.30 development cycle. Maciej
