[OpenMP][WIP] Use ATTACH maps for array-sections/subscripts on pointers.

[abhinavgaba]

This is the initial clang change to support using ATTACH map-type for pointer-attachment.

This includes changes from the following:

• [Offload] Introduce ATTACH map-type support for pointer attachment. #149036
• [Clang][OpenMP] Capture mapped pointers on target by reference. #145454

For example, for the following:

  int *p;
  #pragma omp target enter data map(p[1:10])

The following maps are now emitted by clang:

  (A)
  &p[0], &p[1], 10 * sizeof(p[1]), TO | FROM
  &p, &p[1], sizeof(p), ATTACH

Previously, the two possible maps emitted by clang were:

  (B)
  &p[0], &p[1], 10 * sizeof(p[1]), TO | FROM

  (C)
  &p, &p[1], 10 * sizeof(p[1]), TO | FROM | PTR_AND_OBJ

(B) does not perform any pointer attachment, while (C) also maps the
pointer p, both of which are incorrect.

---

With this change, we are using ATTACH-style maps, like (A), for cases where the expression has a base-pointer. For example:

  int *p, **pp;
  S *ps, **pps;
  ... map(p[0])
  ... map(p[10:20])
  ... map(*p)
  ... map(([20])p)
  ... map(ps->a)
  ... map(pps->p->a)
  ... map(pp[0][0])
  ... map(*(pp + 10)[0])

We also group mapping of clauses with the same base decl in the order of the increasing complexity of their base-pointers, e.g. for something like:

  S **spp;
  map(spp[0][0], spp[0][0].a), // attach-ptr: spp[0]
  map(spp[0]),                // attach-ptr: spp
  map(spp),                   // attach-ptr: N/A

We first map spp, then spp[0] then spp[0][0] and spp[0][0].a.

This allows us to also group "struct" allocation based on their attach pointers.

Cases that need handling:

• When a class member like p is a base-pointer in a map from a member function within the same class, p is not being privatized, instead, we still try to create an implicit map of this[0:1], and access p through that, which is incorrect.

 struct S { int *p;
 void f1() {
   #pragma omp target data map(p[0:1])
      printf("%p %p\n", &p, p);
 }

• Attach-style maps for declare mappers. That should be a separate PR.
• use_device_addr clause does not work properly, because we don't have a proper component-list set-up for it, just one component, so we cannot find the proper attach-ptr. For use_device_addr, we should match existing maps whose attach-ptr matches the attach-ptr of the use_device_addr operand.
• use_device_ptr handling has some issues too. Need debugging.
• Member_of update is not working properly for groups of component-lists after the first one.
• Other issues that haven't been found yet.

Some tests still haven't been updated. These include:

  Clang :: OpenMP/map_struct_ordering.cpp
  Clang :: OpenMP/target_data_use_device_addr_codegen.cpp
  Clang :: OpenMP/target_data_use_device_ptr_codegen.cpp
  Clang :: OpenMP/target_enter_data_codegen.cpp
  Clang :: OpenMP/target_enter_data_depend_codegen.cpp
  Clang :: OpenMP/target_exit_data_codegen.cpp
  Clang :: OpenMP/target_exit_data_depend_codegen.cpp
  Clang :: OpenMP/target_map_codegen_18c.cpp
  Clang :: OpenMP/target_map_codegen_18d.cpp
  Clang :: OpenMP/target_map_codegen_28.cpp
  Clang :: OpenMP/target_map_codegen_29.cpp
  Clang :: OpenMP/target_map_codegen_31.cpp
  Clang :: OpenMP/target_map_codegen_hold.cpp
  Clang :: OpenMP/target_map_deref_array_codegen.cpp
  Clang :: OpenMP/target_map_member_expr_codegen.cpp
  Clang :: OpenMP/target_update_codegen.cpp
  Clang :: OpenMP/target_update_depend_codegen.cpp

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff HEAD~1 HEAD --extensions inc,c,cpp,h -- clang/include/clang/AST/OpenMPClause.h clang/include/clang/Basic/OpenMPKinds.h clang/lib/Basic/OpenMPKinds.cpp clang/lib/CodeGen/CGOpenMPRuntime.cpp clang/lib/Sema/SemaOpenMP.cpp clang/test/OpenMP/bug60602.cpp clang/test/OpenMP/copy-gaps-1.cpp clang/test/OpenMP/copy-gaps-6.cpp clang/test/OpenMP/reduction_implicit_map.cpp clang/test/OpenMP/target_data_codegen.cpp clang/test/OpenMP/target_data_map_codegen_hold.cpp clang/test/OpenMP/target_data_map_pointer_array_subscript_codegen.cpp clang/test/OpenMP/target_data_use_device_addr_codegen.cpp clang/test/OpenMP/target_data_use_device_ptr_codegen.cpp clang/test/OpenMP/target_data_use_device_ptr_if_codegen.cpp clang/test/OpenMP/target_map_array_section_no_length_codegen.cpp clang/test/OpenMP/target_map_both_pointer_pointee_codegen.cpp clang/test/OpenMP/target_map_both_pointer_pointee_codegen_global.cpp clang/test/OpenMP/target_map_codegen_18.inc clang/test/OpenMP/target_map_codegen_19.cpp clang/test/OpenMP/target_map_codegen_20.cpp clang/test/OpenMP/target_map_codegen_21.cpp clang/test/OpenMP/target_map_codegen_22.cpp clang/test/OpenMP/target_map_codegen_23.cpp clang/test/OpenMP/target_map_codegen_26.cpp clang/test/OpenMP/target_map_codegen_27.cpp clang/test/OpenMP/target_map_codegen_33.cpp clang/test/OpenMP/target_map_pointer_defalut_mapper_codegen.cpp clang/test/OpenMP/target_map_ptr_and_star_global.cpp clang/test/OpenMP/target_map_ptr_and_star_local.cpp clang/test/OpenMP/target_map_structptr_and_member_global.cpp clang/test/OpenMP/target_map_structptr_and_member_local.cpp clang/test/OpenMP/target_task_affinity_codegen.cpp llvm/include/llvm/Frontend/OpenMP/OMPConstants.h llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp offload/include/OpenMP/Mapping.h offload/include/device.h offload/include/omptarget.h offload/libomptarget/device.cpp offload/libomptarget/interface.cpp offload/libomptarget/omptarget.cpp offload/plugins-nextgen/amdgpu/src/rtl.cpp offload/plugins-nextgen/common/include/PluginInterface.h offload/plugins-nextgen/common/src/PluginInterface.cpp offload/plugins-nextgen/cuda/src/rtl.cpp offload/plugins-nextgen/host/src/rtl.cpp offload/test/mapping/map_ptr_and_star_global.c offload/test/mapping/map_ptr_and_star_local.c offload/test/mapping/map_ptr_and_subscript_global.c offload/test/mapping/map_ptr_and_subscript_local.c offload/test/mapping/map_structptr_and_member_global.c offload/test/mapping/map_structptr_and_member_local.c

View the diff from clang-format here.

diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index c1a92970c..7f6cc22d0 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -8993,8 +8993,9 @@ private:
             IE->dump();
           }
         }
-        // For use_device_addr, we match an existing map clause if its attach-ptr
-        // is same as the attach-ptr of the use_device_addr clause. e.g.
+        // For use_device_addr, we match an existing map clause if its
+        // attach-ptr is same as the attach-ptr of the use_device_addr clause.
+        // e.g.
         //   map(p) use_device_addr(p)         // match
         //   map(p[1]) use_device_addr(p[0])   // match
         //   map(ps->a) use_device_addr(ps->b) // match
@@ -9762,7 +9763,8 @@ public:
                    ->isPointerType()) || /*&&
                // Check if both component lists share the same attach pointer
                // This allows struct member access through pointers when they
-               // belong to the same struct, including nested cases like ps->qs->x
+               // belong to the same struct, including nested cases like
+               ps->qs->x
                !(AttachPtr1 &&
                  AttachPtr2 &&
                  AttachPtr1 == AttachPtr2)) ||*/

[abhinavgaba]

This is currently failing. Please ignore.

[abhinavgaba]

This test is currently failing. The IR hasn't been updated.

[abhinavgaba]

Please look at the comments in this example to see the maps we are emitting. It's a smaller/easier to read test.

[abhinavgaba]

This shows how we handle mapping of struct-members that have the same attach-ptr. They are allocated as a contiguous chunk.

[abhinavgaba]

The implicit map is because spp is a pointer referenced within the target construct, and neither spp, nor an expression that has spp as its attach-ptr is mapped on the construct.