[llvm-dev] RISC-V LLVM sync-up call 19 Mar 2020

[Evandro Menezes via llvm-dev]

Hi, Sam.

> Thank you for writing this proposal.
> 
> I presume you have seen the FDPIC proposal on the RISC-V sw-dev mailing list [1]. I am keen that any gp-relative relocations that could be shared between the two proposals are shared and compatible with each other - I think this will make a major difference to maintainability and our ability to document these details.

Yes, I have and, at the time it came out, I was designing this code model.  I'm glad that someone else also thought of the GP relative relocations.  Code reuse is always desirable.

> Am I right in thinking your proposal only has one value for `gp` for the whole program, and thus it does not need to be saved or loaded in function prologs and epilogs?

As is current the case, it is callee saved.  Of course, since DSOs have their own small data area, if a function in a DSO built for the compact code model refers to any global data, then it needs to save, restore and setup the GP within it.

Thank you,

__ 
Evandro Menezes ◊ SiFive ◊ Austin, TX

>> On 19 Mar 2020, at 4:19 pm, Evandro Menezes via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> 
>> Here's the draft proposal for the compact code model on RV.  I'd appreciate your feedback before I propose it to the foundation and go about updating the psABI.
>> 
>> Thank you,
>> <Compact Code Model.pdf>
>> 
>> __ 
>> Evandro Menezes ◊ SiFive ◊ Austin, TX
>> 
>>> On Mar 19, 2020, at 8:58, Alex Bradbury via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>> 
>>> For background on these calls, see
>>> <http://lists.llvm.org/pipermail/llvm-dev/2019-September/135087.html>.
>>> 
>>> Reminder: the purpose is to co-ordinate between active contributors.
>>> If you have support questions etc then it's best to post to llvm-dev.
>>> 
>>> We have a call each Thursday at 4pm GMT, via
>>> <https://meet.google.com/ske-zcog-spp>.
>>> 
>>> I've created a shared calendar which may help in keeping track, which
>>> is accessible at:
>>> * <https://calendar.google.com/calendar/b/1?cid=bG93cmlzYy5vcmdfMG41cGtlc2ZqY25wMGJoNWhwczFwMGJkODBAZ3JvdXAuY2FsZW5kYXIuZ29vZ2xlLmNvbQ>
>>> * <https://calendar.google.com/calendar/ical/lowrisc.org_0n5pkesfjcnp0bh5hps1p0bd80%40group.calendar.google.com/public/basic.ics>
>>> 
>>> Issues to discuss today include the following:
>>> * Improving rust code size by not forcing frame pointers
>>> <https://github.com/rust-lang/rust/pull/69890>
>>> * Compact code model (Evandro)
>>> * Update on embedded PIC discussions
>>> * Small data limit <https://reviews.llvm.org/D57497>
>>> * Bitmanip / experimental extension status
>>> * ELF attribute support close to merging
>>> <https://reviews.llvm.org/D75833> <https://reviews.llvm.org/D74023>
>>> * No other topics were submitted, as always, please do submit things
>>> you'd like to discuss
>>> 
>>> Best,
>>> 
>>> Alex
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
> --
> Sam Elliott
> Software Developer - LLVM and OpenTitan
> lowRISC CIC
> 

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