[flang-commits] [flang] [flang][OpenMP] Attach compiler-emitted mappers to arrays of records (PR #179892)

[Kareem Ergawy via flang-commits]

================
@@ -2784,7 +2784,8 @@ genTargetOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
 
           if (!mapperIdName.empty()) {
             bool allowImplicitMapper =
-                semantics::IsAllocatableOrObjectPointer(&sym);
+                semantics::IsAllocatableOrObjectPointer(&sym) ||
+                requiresImplicitDefaultDeclareMapper(*typeSpec);
----------------
ergawy wrote:

Thanks for the suggestion Akash. But, unfortunately, that does not seem to solve the offload issue. With your suggestion, `explicit-and-implicit-record-field-mapping.f90` would still fail if the test is changed to use arrays of records:
```diff
@@ -25,52 +25,52 @@ program reproducer
   use test
   implicit none
   integer          :: i, j
-  TYPE(chunk_type) :: chunk
+  TYPE(chunk_type) :: chunk(1)
 
-  allocate(chunk%tiles(2))
+  allocate(chunk(1)%tiles(2))
   do i = 1, 2
-    allocate(chunk%tiles(i)%field%density0(2, 2))
-    allocate(chunk%tiles(i)%field%density1(2, 2))
+    allocate(chunk(1)%tiles(i)%field%density0(2, 2))
+    allocate(chunk(1)%tiles(i)%field%density1(2, 2))
     do j = 1, 4
-      chunk%tiles(i)%tile_neighbours(j) = j * 10
+      chunk(1)%tiles(i)%tile_neighbours(j) = j * 10
     end do
   end do
 
   !$omp target enter data map(alloc:       &
-  !$omp  chunk%tiles(2)%field%density0)
+  !$omp  chunk(1)%tiles(2)%field%density0)
 
   !$omp target
-    chunk%tiles(2)%field%density0(1,1) = 25
-    chunk%tiles(2)%field%density0(1,2) = 50
-    chunk%tiles(2)%field%density0(2,1) = 75
-    chunk%tiles(2)%field%density0(2,2) = 100
+    chunk(1)%tiles(2)%field%density0(1,1) = 25
+    chunk(1)%tiles(2)%field%density0(1,2) = 50
+    chunk(1)%tiles(2)%field%density0(2,1) = 75
+    chunk(1)%tiles(2)%field%density0(2,2) = 100
   !$omp end target
 
   !$omp target exit data map(from:         &
-  !$omp  chunk%tiles(2)%field%density0)
+  !$omp  chunk(1)%tiles(2)%field%density0)
 
-  if (chunk%tiles(2)%field%density0(1,1) /= 25) then
+  if (chunk(1)%tiles(2)%field%density0(1,1) /= 25) then
     print*, "======= Test Failed! ======="
     stop 1
   end if
 
-  if (chunk%tiles(2)%field%density0(1,2) /= 50) then
+  if (chunk(1)%tiles(2)%field%density0(1,2) /= 50) then
     print*, "======= Test Failed! ======="
     stop 1
   end if
 
-  if (chunk%tiles(2)%field%density0(2,1) /= 75) then
+  if (chunk(1)%tiles(2)%field%density0(2,1) /= 75) then
     print*, "======= Test Failed! ======="
     stop 1
   end if
 
-  if (chunk%tiles(2)%field%density0(2,2) /= 100) then
+  if (chunk(1)%tiles(2)%field%density0(2,2) /= 100) then
     print*, "======= Test Failed! ======="
     stop 1
   end if
 
   do j = 1, 4
-    if (chunk%tiles(2)%tile_neighbours(j) /= j * 10) then
+    if (chunk(1)%tiles(2)%tile_neighbours(j) /= j * 10) then
       print*, "======= Test Failed! ======="
       stop 1
     end if
```
We would still get the runtime crash:
```
explicit extension not allowed: host address specified is 0x00000000002dff90 (72 bytes), but device allocation maps to host at 0x00000000002dff98 (64 bytes)
```

I think the fact that the map is implicit is lost somewhere during MLIR to LLVM translation and this is where I think the fix should be.

https://github.com/llvm/llvm-project/pull/179892