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:
> > > > 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; }
> > ```
> I am afraid that for each SCS in { SCS1, SCS2 }, there is **NOT** always one
> AltiVec type and one generic vector type in { SCS.getFromType(),
> SCS.getToType(2) }. Like following case you mentioned before.
>
>
> ```
> typedef unsigned int GccType __attribute__((__vector_size__(16)));
> typedef __vector unsigned int AltiVecType;
>
> typedef float GccOtherType __attribute__((__vector_size__(16)));
>
> char *f(GccOtherType, int);
> template <typename T> int f(AltiVecType, T);
> template <typename T> int g(AltiVecType, T);
> char *g(GccOtherType, int);
>
> bool zip(GccType v) { return f(v, 0) == g(v, 0); }
> ```
>
> So one choice is keeping current patch and do not handle following ext_vector
> case you gave, the other one is to check there only needs one altivec type in
> { SCS1.getFromType(), SCS1.getToType(2), SCS2.getFromType(),
> SCS2.getToType(2)}, which will handle the following case.
>
> ```
> typedef unsigned int GccType __attribute__((__ext_vector_type__(4)));
> typedef __vector unsigned int AltiVecType;
>
> typedef float GccOtherType __attribute__((__vector_size__(16)));
>
> void f(GccType);
> void f(GccOtherType);
>
> void g(AltiVecType v) { f(v); }
> ```
>
> Then we need accept this behavior. (It's not in testcases)
>
> ```
> typedef char char16 __attribute__ ((__vector_size__ (16)));
> typedef char char16_e __attribute__ ((__ext_vector_type__ (16)));
>
> int &f1(char16);
> int &f1(vector float);
>
> void f1_test( char16_e c16e) {
> f1(c16e); // no error, will choose f1(char16);
> }
> ```
>
>
I //know// that it is not always the case that for each SCS in { SCS1, SCS2 },
there is one AltiVec type and one generic vector type in { SCS.getFromType(),
SCS.getToType(2) }. What I mean is that when it is indeed not the case, we may
consider not applying the extra ordering between SCS1 and SCS2. This does mean
that the case I mentioned before remains ambiguous; however, that may be
acceptable.
https://reviews.llvm.org/D53417
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