[PATCH] D62960: Add SVE opaque built-in types

[John McCall via Phabricator via cfe-commits]

rjmccall added inline comments.


================
Comment at: lib/AST/ItaniumMangle.cpp:2680
+    break;
+#include "clang/Basic/AArch64SVEACLETypes.def"
   }
----------------
rsandifo-arm wrote:
> rovka wrote:
> > erik.pilkington wrote:
> > > rsandifo-arm wrote:
> > > > erik.pilkington wrote:
> > > > > jfb wrote:
> > > > > > @rjmccall you probably should review this part.
> > > > > Sorry for the drive by comment, but: All of these mangling should really be using the "vendor extension" production IMO:
> > > > > 
> > > > > `<type> ::= u <source-name>`
> > > > > 
> > > > > As is, these manglings intrude on the users's namespace, (i.e. if they had a type named `objc_selector` or something), and confuse demanglers which incorrectly assume these are substitutable (vendor extension builtin types are substitutable too though, but that should be handled here).
> > > > It isn't obvious from the patch, but the SVE names that we're mangling are predefined names like __SVInt8_t. rather than user-facing names like svint8_t  The predefined names and their mangling are defined by the platform ABI (https://developer.arm.com/docs/100986/0000), so it wouldn't be valid for another part of the implementation to use those names for something else.
> > > > 
> > > > I realise you were making a general point here though, sorry.
> > > > 
> > > The mangling in the document you linked does use the vendor extension production here though, i.e. the example is `void f(int8x8_t)`, which mangles to _Z1f**u10__Int8x8_t**. It is true that this shouldn't ever collide with another mangling in practice, but my point is there isn't any need to smuggle it into the mangling by pretending it's a user defined type, when the itanium grammar and related tools have a special way for vendors to add builtin types.
> > I agree with Erik here, the example in the PCS document seems to suggest using u. I think either the patch needs to be updated or the document needs to be more clear about what the mangling is supposed to look like.
> Thanks for highlighting this problem, and sorry for not noticing myself when pointing you at the doc.
> 
> Unfortunately, the specification and implementation already difer for the Advanced SIMD types, with both clang and GCC omitting the 'u' despite the spec saying it should be present.  So we're considering changing the spec to match what's now the de facto ABI.
> 
> For SVE we do still have the opportunity to use 'u'.  I've left it as-is for now though, until we've reached a decision about whether to follow existing practice for Advanced SIMD or whether to do what the spec says.
These do seem more "builtin" than the SIMD types, but I don't think it deeply matters either way, since these are already reserved names.


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  rC Clang

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  https://reviews.llvm.org/D62960/new/

https://reviews.llvm.org/D62960