[lowrisc-dev] Codename for architecture (GNU autotools, etc)?

Manuel A. Fernandez Montecelo manuel.montezelo at gmail.com
Sat Nov 1 15:01:49 GMT 2014


Hi,

According to the website, the processor used will be RISC-V 64 bits.  I
could not find any mentions about the endianness or other details that I
am interested in.  Follows a preamble, doubts at bottom.


In the most recent version of config.sub of autotools [1], there are
only the strings "riscv32 | riscv64".  In config.guess [2], there's
nothing matching "riscv".

[1] http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD
[2] http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD


In recent times and for the most popular devices, ARM seems to go mostly
with little endian, but there are also big-endian systems.  IBM created
and seems to be investing more effort in ppc64el after having ppc64,
because apparently there is a stronger demand for customers.  MIPS have
also mips/mipsel and mips64/mips64el.  In these cases (and same for many
other CPUs), they have "registered" the full range of architecture names
in these GNU autotools files, while there is only the aforementioned
"riscv32 | riscv64" for RISC-V, with no "le/el" or "be/eb" attached.


So, my doubts are:

- RISC-V is little-endian in principle, so I guess that the names above
  "riscv32 | riscv64" will imply little-endianness, but the ISA manual
  says that there can be big or bi-endian variants.

  Which one does lowRISC plan to use?  And what will be the codename of
  the architecture in that case -- "riscv64el/-le", "riscv64eb/-be", or
  just plainly "riscv64" (implying little endian)?


- Does lowRISC plan to use different extensions or modifications of
  RISC-V, so that the architecture name will be different from
  "riscv64*" in any case?


- What would be the architecture triplet name, for GNU toolchain?  The
  compiler from RISC-V github repositories so far provides:
  riscv64-unknown-linux-gnu.


Maybe some of these questions are not decided yet, or things like naming
in GNU autotools files depend mostly on decisions to be taken by RISC-V
folks rather than people involved in list...  But I would be grateful of
any information and pointers that you can provide.


Cheers and thanks in advance.
--
Manuel A. Fernandez Montecelo <manuel.montezelo at gmail.com>



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