rjmccall added inline comments.
================
Comment at: lib/Sema/TreeTransform.h:5363
+ if (ResultType.getAddressSpace() != LangAS::Default &&
+ (ResultType.getAddressSpace() != LangAS::opencl_private)) {
SemaRef.Diag(TL.getReturnLoc().getBeginLoc(),
----------------
Anastasia wrote:
> rjmccall wrote:
> > Anastasia wrote:
> > > Anastasia wrote:
> > > > rjmccall wrote:
> > > > > Anastasia wrote:
> > > > > > I am trying to be a bit more helpful here although I am not sure if
> > > > > > we should instead require explicit template parameter and fail the
> > > > > > template deduction instead.
> > > > > >
> > > > > > Basically, do we want the following code to always require
> > > > > > specifying template argument explicitly:
> > > > > >
> > > > > >
> > > > > > ```
> > > > > > template <class T>
> > > > > > T xxx(T *in) {
> > > > > > T *i = in;
> > > > > > return *i;
> > > > > > }
> > > > > >
> > > > > > __kernel void test() {
> > > > > > int foo[10];
> > > > > > xxx<int>(&foo[0]); // if we deduce type from foo, it ends up
> > > > > > being qualified by __private that we currently diagnose. However
> > > > > > private is default (implicit) address space for return type so
> > > > > > technically there is no danger in just allowing xxx(&foo[0])
> > > > > > }
> > > > > > ```
> > > > > Implicitly ignoring all address-space qualifiers on the return type
> > > > > seems like the right thing to do; I don't think it needs to be
> > > > > limited to `__private`. That's probably also the right thing to do
> > > > > for locals, but I'm less certain about it.
> > > > Just to clarify by "Implicitly ignoring" you mean ignoring if the templ
> > > > parameters were deduced?
> > > >
> > > > Although I am a bit concerned about allowing other than `__private`
> > > > address spaces in return types as we reject them in return types of
> > > > functions generally. Would it not be somehow inconsistent?
> > > Ok, I have removed the diagnostic completely. At least we don't seem to
> > > generate any incorrect IR.
> > They should be diagnosed somehow when written explicitly on a return type,
> > but if you just do that on the parser path you don't have to worry about it
> > during template instantiation. They should probably otherwise be ignored
> > no matter where they came from — if someone typedefs `private_int_t` to
> > `__private int`, you should just treat that as `int` in a return type.
> > Stripping the qualifier from the type is probably the right thing to do so
> > that it doesn't further impact semantic analysis.
> >
> > I definitely don't think you want a model where the qualifier actually
> > means that the return is somehow done via an object in that address space.
> > They should be diagnosed somehow when written explicitly on a return type,
> > but if you just do that on the parser path you don't have to worry about it
> > during template instantiation.
>
> Ok, this seems to be working currently. The following won't compile:
>
> ```
> template <typename T>
> struct S {
> __global T f1(); // error: return value cannot be qualified with
> address space
> };
>
> ```
>
> > They should probably otherwise be ignored no matter where they came from —
> > if someone typedefs private_int_t to __private int, you should just treat
> > that as int in a return type.
>
> We produce diagnostic for this case currently. I can update this in a
> separate patch if you think it's more helpful behavior. Although I feel a bit
> worried about it. However it would align with what we are doing with
> templates here... so perhaps it's logical change...
>
> > Stripping the qualifier from the type is probably the right thing to do so
> > that it doesn't further impact semantic analysis.
>
> I guess you mean stripping quals for the case of typedef or others where we
> will accept the code and ignore quals on the return type? I have tried to do
> this just for the template case but there are some assertions firing because
> we are expecting the original return type to be the same before and after
> template instantiation. So it feels like I would have to do it for everything
> together. Maybe it should rather go into separate review?
> We produce diagnostic for this case currently. I can update this in a
> separate patch if you think it's more helpful behavior. Although I feel a bit
> worried about it. However it would align with what we are doing with
> templates here... so perhaps it's logical change...
Well, it's debatable. C doesn't say that qualifiers are erased in function
return types in general. On the other hand, qualifiers are semantically
meaningless there, and C has few rules that rely on exact type identity. On
reflection, we should probably keep diagnosing that at parse-time, even for
typedefs, and just ignore it in templates.
Can you point out which assertion is firing?
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D62584/new/
https://reviews.llvm.org/D62584
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