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:
> > hubert.reinterpretcast wrote:
> > > 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.
> > Sorry, typo in the above case:
> > ```
> > typedef unsigned int GccType __attribute__((__ext_vector_type__(4)));
> > ```
> >
> OK, I understand what's your meaning. I just wanted to give you the condition
> of what your case showed. Thank you.
>
> In my opinion, I don't think AltiVec/__ext_vector_type__ conversions are
> available. Because
> 1. __vector_size__/__ext_vector_type__ conversion is not available
> 2. "This class enables syntactic extensions, like Vector Components for
> accessing......" (as ExtVectorType comments said). So we'd better handle
> separately.
>
> What do you think of this?
AltiVec/`__ext_vector_type__` conversions are available.
```
typedef unsigned int GccType __attribute__((__ext_vector_type__(4)));
typedef __vector unsigned int AltiVecType;
AltiVecType f(GccType v) { return v; }
```
https://reviews.llvm.org/D53417
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