sdesmalen added a subscriber: keith.walker.arm.
sdesmalen added inline comments.
================
Comment at: lib/CodeGen/CGDebugInfo.cpp:1101
case CC_AAPCS:
+ case CC_AArch64VectorCall:
return llvm::dwarf::DW_CC_LLVM_AAPCS;
----------------
rjmccall wrote:
> rnk wrote:
> > sdesmalen wrote:
> > > I wasn't really sure whether this requires a corresponding
> > > DW_CC_LLVM_AAVPCS record in LLVM, as I couldn't find much about the
> > > DW_CC_LLVM_ encodings, specifically whether they align with some agreed
> > > encoding that is implemented by GDB/LLDB. Is this defined anywhere, or is
> > > it ignored by debuggers at the moment?
> > DWARF only allows encoding 256 conventions, and we grabbed 0xC[0-F], I
> > guess for "clang", so we probably want to be careful about adding another.
> > Do you anticipate making debuggers able to call such functions? If not,
> > it's probably not worth it.
> They probably should be callable.
>
> It looks like DWARF reserves the first 64 conventions for general/language
> purposes and treats the rest of the range as "user" conventions. If those
> conventions are assumed to be universally unique, that's a really limiting
> schema once you started dividing it up by vendor. If I might make a
> suggestion, while there are certainly many calling conventions that are meant
> to have universal meaning (e.g. most language-specific conventions), there
> are also a large number that are inherently target-specific. DWARF already
> uses a lot of numbers that only make sense in the context of a target (like
> register numbers); it would make sense for DWARF to carve out a range of the
> encoding space (maybe 16 or 32 numbers) for target-specific CCs. This is
> hardly the first example; consider also all the variant ARM32 CCs or the i386
> fastcall CC.
Great feedback. I think this discussion has a wider scope than this patch and I
think its probably best to keep this change as-is for now. We'll first work to
add a section to the 'DWARF for the ARM 64-bit Architecture' document
describing a DW_AT_calling_convention value for the AArch64 vector PCS and will
create a separate patch to LLVM/Clang to implement its support. I've also asked
@keith.walker.arm to raise this (encoding space) as a topic with the DWARF
standardization committee.
https://reviews.llvm.org/D54425
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
