[OpenMP][Flang][Semantics] Add semantics support for USE_DEVICE_PTR c…

…lause on OMP TARGET DATA directive.

Initial support for USE_DEVICE_PTR clause on OMP TARGET DATA directive.

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D148254

flang/docs/OpenMP-semantics.md

@@ -318,6 +318,7 @@ w/
 For the following OpenMP regions:
 
 * `target` regions
+* `target data` regions
 * `teams` regions
 * `parallel` regions
 * `simd` regions
@@ -407,6 +408,16 @@ More details are listed in the following table:
    <td>OmpLastPrivate
    </td>
   </tr>
+  <tr>
+   <td>use_device_ptr
+   </td>
+   <td>Yes
+   </td>
+   <td>New Symbol
+   </td>
+   <td>OmpUseDevicePtr
+   </td>
+  </tr>
 </table>
 
 To determine the right data-sharing attribute,
@@ -519,6 +530,12 @@ will be determined and represented as `Flag` in the `Symbol` object
 of the variable.
 No `Symbol` or `Scope` will be created.
 
+However, there are some exceptions for this, Pointers that appear in a
+use_device_ptr clause are privatized and the device pointers to the
+corresponding list items in the device data environment are assigned into the
+private versions so it is best to follow the representation for privatised
+variables i.e represent them with a new Symbol and `OmpUseDevicePtr` flag.
+
 The basic steps to determine the data-mapping attribute are:
 
 1. If _map_ clause is present,

flang/include/flang/Semantics/symbol.h

@@ -560,6 +560,7 @@ class Symbol {
       OmpShared, OmpPrivate, OmpLinear, OmpFirstPrivate, OmpLastPrivate,
       // OpenMP data-mapping attribute
       OmpMapTo, OmpMapFrom, OmpMapAlloc, OmpMapRelease, OmpMapDelete,
+      OmpUseDevicePtr,
       // OpenMP data-copying attribute
       OmpCopyIn, OmpCopyPrivate,
       // OpenMP miscellaneous flags

flang/lib/Parser/openmp-parsers.cpp

@@ -309,7 +309,7 @@ TYPE_PARSER(
     "TO" >> construct<OmpClause>(construct<OmpClause::To>(
                 parenthesized(Parser<OmpObjectList>{}))) ||
     "USE_DEVICE_PTR" >> construct<OmpClause>(construct<OmpClause::UseDevicePtr>(
-                            parenthesized(nonemptyList(name)))) ||
+                            parenthesized(Parser<OmpObjectList>{}))) ||
     "UNIFIED_ADDRESS" >>
         construct<OmpClause>(construct<OmpClause::UnifiedAddress>()) ||
     "UNIFIED_SHARED_MEMORY" >>

flang/lib/Semantics/check-omp-structure.cpp

@@ -2766,11 +2766,12 @@ const parser::OmpObjectList *OmpStructureChecker::GetOmpObjectList(
     const parser::OmpClause &clause) {
 
   // Clauses with OmpObjectList as its data member
-  using MemberObjectListClauses = std::tuple<parser::OmpClause::Copyprivate,
-      parser::OmpClause::Copyin, parser::OmpClause::Firstprivate,
-      parser::OmpClause::From, parser::OmpClause::Lastprivate,
-      parser::OmpClause::Link, parser::OmpClause::Private,
-      parser::OmpClause::Shared, parser::OmpClause::To>;
+  using MemberObjectListClauses =
+      std::tuple<parser::OmpClause::Copyprivate, parser::OmpClause::Copyin,
+          parser::OmpClause::Firstprivate, parser::OmpClause::From,
+          parser::OmpClause::Lastprivate, parser::OmpClause::Link,
+          parser::OmpClause::Private, parser::OmpClause::Shared,
+          parser::OmpClause::To, parser::OmpClause::UseDevicePtr>;
 
   // Clauses with OmpObjectList in the tuple
   using TupleObjectListClauses = std::tuple<parser::OmpClause::Allocate,

flang/lib/Semantics/resolve-directives.cpp

@@ -436,6 +436,11 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
     return false;
   }
 
+  bool Pre(const parser::OmpClause::UseDevicePtr &x) {
+    ResolveOmpObjectList(x.v, Symbol::Flag::OmpUseDevicePtr);
+    return false;
+  }
+
   void Post(const parser::Name &);
 
   // Keep track of labels in the statements that causes jumps to target labels
@@ -506,7 +511,7 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
       Symbol::Flag::OmpPrivate, Symbol::Flag::OmpLinear,
       Symbol::Flag::OmpFirstPrivate, Symbol::Flag::OmpLastPrivate,
       Symbol::Flag::OmpReduction, Symbol::Flag::OmpCriticalLock,
-      Symbol::Flag::OmpCopyIn};
+      Symbol::Flag::OmpCopyIn, Symbol::Flag::OmpUseDevicePtr};
 
   static constexpr Symbol::Flags ompFlagsRequireMark{
       Symbol::Flag::OmpThreadprivate};

flang/lib/Semantics/resolve-names.cpp

@@ -1414,7 +1414,6 @@ bool OmpVisitor::NeedsScope(const parser::OpenMPBlockConstruct &x) {
   const auto &beginBlockDir{std::get<parser::OmpBeginBlockDirective>(x.t)};
   const auto &beginDir{std::get<parser::OmpBlockDirective>(beginBlockDir.t)};
   switch (beginDir.v) {
-  case llvm::omp::Directive::OMPD_target_data:
   case llvm::omp::Directive::OMPD_master:
   case llvm::omp::Directive::OMPD_ordered:
   case llvm::omp::Directive::OMPD_taskgroup:

flang/test/Semantics/OpenMP/use_device_ptr.f90

@@ -0,0 +1,21 @@
+! RUN: %flang -fc1 -fopenmp -fdebug-dump-symbols %s | FileCheck %s
+! OpenMP Version 5.0
+! 2.10.1 use_device_ptr clause
+! List items that appear in a use_device_ptr clause are converted into device
+! pointers to the corresponding list item in the device data environment.
+
+subroutine omp_target_data
+   use iso_c_binding
+   integer :: a(1024)
+   !CHECK: b size=8 offset=4096: ObjectEntity type: TYPE(c_ptr)
+   type(C_PTR) :: b
+   integer, pointer :: arrayB
+   a = 1
+   !$omp target data map(tofrom: a, arrayB) use_device_ptr(b)
+   !CHECK: b (OmpUseDevicePtr)
+      allocate(arrayB)
+      call c_f_pointer(b, arrayB)
+      a = arrayB
+   !$omp end target data
+end subroutine omp_target_data
+

llvm/include/llvm/Frontend/OpenMP/OMP.td

@@ -295,8 +295,7 @@ def OMPC_From : Clause<"from"> {
 }
 def OMPC_UseDevicePtr : Clause<"use_device_ptr"> {
   let clangClass = "OMPUseDevicePtrClause";
-  let flangClass = "Name";
-  let isValueList = true;
+  let flangClass = "OmpObjectList";
 }
 def OMPC_IsDevicePtr : Clause<"is_device_ptr"> {
   let clangClass = "OMPIsDevicePtrClause";