ABataev added inline comments.
================
Comment at: clang/lib/CodeGen/CGOpenMPRuntime.cpp:9470-9471
+ MappedVarSet.insert(CI->getCapturedVar()->getCanonicalDecl());
+ else
+ MappedVarSet.insert(nullptr);
if (CurBasePointers.empty())
----------------
jdenny wrote:
> ABataev wrote:
> > jdenny wrote:
> > > ABataev wrote:
> > > > No need to insert `nullptr` here, it is not used later.
> > > Without this `nulltpr` insertion, many tests fail because of duplicate
> > > map entries. Independently of my patch, `nulltptr` is used to indicate
> > > `this` capture (see the `generateInfoForCapture` implementation) .
> > >
> > > For example:
> > >
> > > ```
> > > struct S {
> > > int i;
> > > void foo() {
> > > #pragma omp target map(i)
> > > i = 5;
> > > }
> > > };
> > > ```
> > >
> > > We should have:
> > >
> > > ```
> > > @.offload_maptypes = private unnamed_addr constant [2 x i64] [i64 32, i64
> > > 281474976710659]
> > > ```
> > >
> > > Without the `nullptr` insertion, we have:
> > >
> > > ```
> > > @.offload_maptypes = private unnamed_addr constant [4 x i64] [i64 32, i64
> > > 281474976710659, i64 32, i64 844424930131971]
> > > ```
> > This is strange, because you don't check for `nullptr`. You only check for
> > `ValueDecl`s, but not capture of `this`.
> I'm not sure what code you're referring to when you say "you check".
>
> Both with and without my patch, my understanding is that `nullptr` is a
> special key that means `this`. I'm depending on that to avoid generating map
> entries twice for `this`.
>
> My understanding is based on the way `generateInfoForCapture` works. If
> `Cap->capturesThis()`, then `VD = nullptr`. That `VD` is then used by
> `C->decl_component_lists(VD)` to find entries for `this` in map clauses.
>
> Unless I'm misreading it, the code that sets `nullptr` for `this` in decl
> components is `checkMappableExpressionList` in SemaOpenMP.cpp. The last few
> lines of that function have a comment to this effect. (That comment would
> probably be more useful in a header file somewhere.)
`MappedVarSet` is a new variable, right? It is used only in 2 places: here,
where you add elements to this set, and in `generateAllInfo` where you have a
check:
```
if (SkipVarSet.count(VD))
return;
```
I don't see other places where it is used. And I don't see places where you
check for the presence of `nullptr` in this set. That's why I think you don't
need to add it, if you don't check for its presence later.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D83922/new/
https://reviews.llvm.org/D83922
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