On Mon, Nov 7, 2022 at 8:01 PM Palmer Dabbelt <pal...@rivosinc.com> wrote:
> The docs say we take ISA strings, but that's never really been the case: > at a bare minimum we've required lower case strings, but there's > generally been some subtle differences as well in things like version > handling and such. We talked about removing the lower case requirement > in the last GNU toolchain meeting and we've always called other > differences just bugs. We don't have profile support yet, but based on > the discussions on the RISC-V lists it looks like we're going to have > some differences there as well. > So let's just stop pretending these are ISA strings. That's been a > headache for years now, if we're meant to just be ISA-string-like here > then we don't have to worry about all these long-tail ISA string parsing > issues. > You are right, we should first properly specify the -march string, before we talk about the implementation details of the parser. I tried to collect all the recent change requests and undocumented properties of the -march string and worked on a first draft specification. As the -march flag should share a common behavior across different compilers and tools, I've made a PR to the RISC-V toolchain-conventions repo: https://github.com/riscv-non-isa/riscv-toolchain-conventions/pull/26 Do you mind if we continue the discussion there? > > Link: https://lists.riscv.org/g/sig-toolchains/message/486 > > gcc/ChangeLog > > doc/invoke.texi (RISC-V): -march doesn't take ISA strings. > > --- > > This is now woefully under-documented, as we can't even fall back on the > "it's just an ISA string" excuse any more. I'm happy to go document > that, but figured I'd just send this along now so we can have the > discussion. > --- > gcc/doc/invoke.texi | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > index 94a2e20cfc1..780b0364c52 100644 > --- a/gcc/doc/invoke.texi > +++ b/gcc/doc/invoke.texi > @@ -28617,11 +28617,11 @@ Produce code conforming to version 20191213. > The default is @option{-misa-spec=20191213} unless GCC has been configured > with @option{--with-isa-spec=} specifying a different default version. > > -@item -march=@var{ISA-string} > +@item -march=@var{target-string} > @opindex march > -Generate code for given RISC-V ISA (e.g.@: @samp{rv64im}). ISA strings > must be > -lower-case. Examples include @samp{rv64i}, @samp{rv32g}, @samp{rv32e}, > and > -@samp{rv32imaf}. > +Generate code for given target (e.g.@: @samp{rv64im}). Target strings > are > +similar to ISA strings, but must be lower-case. Examples include > @samp{rv64i}, > +@samp{rv32g}, @samp{rv32e}, and @samp{rv32imaf}. > > When @option{-march=} is not specified, use the setting from > @option{-mcpu}. > > -- > 2.38.1 > >
