hubert.reinterpretcast added inline comments.
================
Comment at: clang/lib/Sema/SemaOverload.cpp:3913
+ for (auto Type : Types) {
+ if (S.Context.getCanonicalType(Type)->getTypeClass() != Type::Vector)
+ return false;
----------------
wuzish wrote:
> hubert.reinterpretcast wrote:
> > wuzish wrote:
> > > hubert.reinterpretcast wrote:
> > > > wuzish wrote:
> > > > > hubert.reinterpretcast wrote:
> > > > > > Considering that this is a local lambda called in one place, are we
> > > > > > expecting cases where the canonical type is not something on which
> > > > > > we can call getVectorKind()? If not, then we do not need this `if`.
> > > > > Well, that's for ExtVectorType. I encounter some testcase failure
> > > > > because of that. So I just narrow the condition to only handle
> > > > > Type::Vector.
> > > > >
> > > > > As the following comment said, so I treat it separately.
> > > > >
> > > > > /// ExtVectorType - Extended vector type. This type is created using
> > > > > /// __attribute__((ext_vector_type(n)), where "n" is the number of
> > > > > elements.
> > > > > /// Unlike vector_size, ext_vector_type is only allowed on typedef's.
> > > > > This
> > > > > /// class enables syntactic extensions, like Vector Components for
> > > > > accessing
> > > > > /// points (as .xyzw), colors (as .rgba), and textures (modeled after
> > > > > OpenGL
> > > > > /// Shading Language).
> > > > An ExtVectorType is a VectorType, so what sort of failures are you
> > > > hitting?
> > > Yes. But the TypeClass of ExtVectorType is ExtVector.
> > >
> > > some test points check the error report for ambiguous call because of too
> > > many implicit cast choices from ext_vector_type to vector type. Such as
> > > blow.
> > >
> > >
> > > ```
> > > typedef char char16 __attribute__ ((__vector_size__ (16)));
> > > typedef long long longlong16 __attribute__ ((__vector_size__ (16)));
> > > typedef char char16_e __attribute__ ((__ext_vector_type__ (16)));
> > > typedef long long longlong16_e __attribute__ ((__ext_vector_type__ (2)));
> > >
> > >
> > > void f1_test(char16 c16, longlong16 ll16, char16_e c16e, longlong16_e
> > > ll16e) {
> > > int &ir1 = f1(c16);
> > > float &fr1 = f1(ll16);
> > > f1(c16e); // expected-error{{call to 'f1' is ambiguous}}
> > > f1(ll16e); // expected-error{{call to 'f1' is ambiguous}}
> > > }
> > > ```
> > >
> > > If we are gonna widen the condition, we can make a follow-up patch. Or we
> > > need include this condition and do this together in this patch?
> > The widening that has occurred is in allowing the scope of the change to
> > encompass cases where AltiVec vectors are not sufficiently involved. The
> > change in behaviour makes sense, and perhaps the community may want to
> > pursue it; however, the mandate to make that level of change has not been
> > given.
> >
> > I do not believe that requiring that the TypeClass be VectorType is the
> > correct narrowing of the scope. Instead, we may want to consider requiring
> > that for each `SCS` in { `SCS1`, `SCS2` }, there is one AltiVec type and
> > one generic vector type in { `SCS.getFromType()`, `SCS.getToType(2)` }.
> >
> The key point is that ExtVector is a kind of typeclass, **and** its vector
> kind is generic vector type.
>
> So you think we should encompass ext_vector cases as a part of the scope of
> this patch? And modify the above cases' expected behavior (remove the
> **expected-error**)?
I gave a concrete suggested narrowing of the scope that does not exclude
ExtVectorType or other derived types of VectorType. It also does not change the
behaviour of the `f1_test` case above. We could pursue additional discussion
over that case (separable from the current patch) on the mailing list.
I believe my suggestion does do something about this case:
```
typedef unsigned int GccType __attribute__((__ext_vector_type__(16)));
typedef __vector unsigned int AltiVecType;
typedef float GccOtherType __attribute__((__vector_size__(16)));
void f(GccType);
void f(GccOtherType);
void g(AltiVecType v) { f(v); }
```
I think that addressing the latter case is within the realm of things that we
should consider for this patch. Either way, we should ensure that tests for
AltiVec/__ext_vector_type__ conversions are available.
https://reviews.llvm.org/D53417
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