Messages in this thread | | | Date | Fri, 10 May 2024 14:43:10 -0700 | From | Charlie Jenkins <> | Subject | Re: [PATCH v2 2/8] riscv: Add PLATFORM_MAY_SUPPORT_RISCV_ISA_V Kconfig option |
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On Fri, May 10, 2024 at 09:43:33PM +0100, Conor Dooley wrote: > Hey Charlie, > > On Tue, May 07, 2024 at 06:36:28PM -0700, Charlie Jenkins wrote: > > Current versions of the kernel add "v" to the march and then immeidately > > filter it out such that "v" is not passed to CFLAGS. Instead of doing > > this filtering, code blocks in the kernel that want to use vector > > assembly have been changed to locally enable vector (using ".option > > arch, +v"). > > Other content in the series aside, since this is a change that could be > made independently of the main series objectives, I figured it was worth > pointing out that this is not a change without downsides: I think that > it would drop support for vector with most versions of LLVM as > .option arch support there is much more recent thing than it is for gcc. > Off the top of my head I don't know exactly the versions involved, but > it is something like LLVM-14 supports vector but only LLVM-17 and later > supports .option arch.
Toolchain incompatibilities are always fun. It does look like .option arch was introduced in LLVM-17. That would be a regression. We do use option arch for every other extension, but vector was treated special when it was introduced unfortunately so maybe we have to live with the weird march parsing hack.
- Charlie
> > Thanks, > Conor.
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