[OE-core] ARC: machine dictionary - ARCompact vs ARCv2

[Khem Raj]

On Tue, Sep 25, 2018 at 4:57 AM Alexey Brodkin
<alexey.brodkin at synopsys.com> wrote:
>
> Hello,
>
> While upstreaming ARC bits in OE core I faced one interesting challenge.
>
> As of today we have 2 binary-incompatible 32-bit ISAs (Instruction Set Arch):
>  1. ARCompact (AKA ARCv1) and
>  2. ARCv2
>
> In Binutils they have 2 separate machine numbers: EM_ARC_COMPACT=93 for ARCompact,
> see [1] and EM_ARC_COMPACT2=195 for ARCv2, see [2].
>
> Still we call them both "arc" and so I'm not sure what would be the right way
> of handling that mess in OE's machine dictionary.

mess is the right word. My preference would be to keep the newer
one in OE as the support is new,

>
> For now I just have separate instances of "arc_machine_dict" for ARCompact [3]
> and ARCv2 [4] and depending on what a given OE "machine" includes as "tune-arcX.inc"
> build system uses one or another dictionary entry.
>
> Even though it works fine it doesn't fit into common dictionary in meta/lib/oe/elf.py.
>
> Any suggestions on how ARC machine dictionary might be upstreamed?

you can define a separate arch like x32 is for x86_64 arch. but I think
PACKAGEQA_EXTRA_MACHDEFFUNCS is a way to hook in such ana

>
> -Alexey
>
> [1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=include/elf/common.h;h=e194274305663f565c6beee5ec21dbed70cdac46;hb=HEAD#l202
> [2] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=include/elf/common.h;h=e194274305663f565c6beee5ec21dbed70cdac46;hb=HEAD#l309
> [3]
> https://github.com/foss-for-synopsys-dwc-arc-processors/meta-synopsys/blob/083958dedbd60c022432a17e952638a41e37c3dc/conf/machine/include/tune-arcompact.inc#L25
> [4]
> https://github.com/foss-for-synopsys-dwc-arc-processors/meta-synopsys/blob/083958dedbd60c022432a17e952638a41e37c3dc/conf/machine/include/tune-arcv2.inc#L38