[clang] [llvm] [Clang][OpenMP] Capture mapped pointers on `target` by reference. (PR #145454)

[Abhinav Gaba via cfe-commits]

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@@ -8811,8 +8829,19 @@ class MappableExprsHandler {
         ++EI;
       }
     }
-    llvm::stable_sort(DeclComponentLists, [](const MapData &LHS,
-                                             const MapData &RHS) {
+    llvm::stable_sort(DeclComponentLists, [VD](const MapData &LHS,
+                                               const MapData &RHS) {
+      // For cases like map(p, p[0], p[0][0]), the shortest map, like map(p)
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abhinavgaba wrote:

And I'm also not sure yet the lambda captures function would interact with this if we split g`enerateInfoForCapture.

> 2. What if we have 3-level dependency, will we need the third loop in this case?

For a three-level pointer case like this:

`map(to: sp->x, sp->y) map(to: sp->sq->a, sp->sq->b) map(to: sp->sq->sr->c, sp->sq->sr->d) map(sp)`

We should eventually have something like:
```
&sp, &sp, sizeof(sp), TO | PARAM

// map-chain for the containing-struct sp[0] with base-pointer sp
&sp[0], &sp[0], sizeof(sp[0]), ALLOC
&sp[0], &sp->x, sizeof(sp->x), TO | MEMBER_OF(2)
&sp[0], &sp->y, sizeof(sp->y), TO | MEMBER_OF(2)
&sp, &sp[0], ATTACH

// map-chain for the containing-struct sp->sq[0] with base-pointer sp->sq
&(sp->sq[0]), &(sp->sq[0]), sizeof(sp->sq[0]), ALLOC
&sp->sq[0], &sp->sq->a, sizeof(sp->sq->a), TO | MEMBER_OF(6)
&sp->sq[0], &sp->sq->a, sizeof(sp->sq->a), TO | MEMBER_OF(6)
&sp->sq, &sp->sq[0], ATTACH

// map-chain for the containing-struct sp->sq->sr[0] with base-pointer sp->sq->sr
&(sp->sq->sr[0]), &(sp->sq->sr[0]), sizeof(sp->sq->sr[0]), ALLOC
&sp->sq->sr[0], &sp->sq->sr->c, sizeof(sp->sq->sr->c), TO | MEMBER_OF(10)
&sp->sq->sr[0], &sp->sq->sr->d, sizeof(sp->sq->sr->d), TO | MEMBER_OF(10)
&sp->sq->sr, &sp->sq->sr[0], ATTACH
```

The `for (Expr* AttachBasePtr: AttachBasePtrs)` loop would need to run three times, once each for the for the attachable-base-pointer `sp`, `sp->sq`, and `sp->sq->sr`.

And we can think of the first invocation to be for the component-lists that have no base-pointer, and pull that into the loop as well.


https://github.com/llvm/llvm-project/pull/145454