[clang][OpenMP] 6.0: Add default clause support for 'target' directive (#162910)

Per OpenMP 6.0 specification, section 7.5.1, default Clause

Page 224, lines 3-5 default Clause, Semantics
  If data-sharing-attribute is shared then the clause has no effect
  on a target construct; otherwise, its effect on a target construct is
  equivalent to specifying the defaultmap clause with the same
  data-sharing-attribute and variable-category.

Testing:
  OpenMP LIT tests
  check-all

Author: ddpagan

clang/docs/OpenMPSupport.rst

@@ -559,7 +559,7 @@ implementation.
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+
 | Clarifications to Fortran map semantics                     | :none:`unclaimed`         | :none:`unclaimed`         |                                                                          |
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+
-| default clause at target construct                          | :part:`In Progress`       | :none:`unclaimed`         |                                                                          |
+| default clause at target construct                          | :good:`done`              | :none:`unclaimed`         | https://github.com/llvm/llvm-project/pull/162910                         |
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+
 | ref count update use_device_{ptr, addr}                     | :none:`unclaimed`         | :none:`unclaimed`         |                                                                          |
 +-------------------------------------------------------------+---------------------------+---------------------------+--------------------------------------------------------------------------+

clang/docs/ReleaseNotes.rst

@@ -725,6 +725,7 @@ OpenMP Support
 - Added support for 'omp fuse' directive.
 - Updated parsing and semantic analysis support for ``nowait`` clause to accept
   optional argument in OpenMP >= 60.
+- Added support for ``default`` clause on ``target`` directive.
 
 Improvements
 ^^^^^^^^^^^^

clang/lib/Sema/SemaOpenMP.cpp

@@ -17319,45 +17319,101 @@ OMPClause *SemaOpenMP::ActOnOpenMPDefaultClause(
         << getOpenMPClauseNameForDiag(OMPC_default);
     return nullptr;
   }
-
-  switch (M) {
-  case OMP_DEFAULT_none:
-    DSAStack->setDefaultDSANone(MLoc);
-    break;
-  case OMP_DEFAULT_shared:
-    DSAStack->setDefaultDSAShared(MLoc);
-    break;
-  case OMP_DEFAULT_firstprivate:
-    DSAStack->setDefaultDSAFirstPrivate(MLoc);
-    break;
-  case OMP_DEFAULT_private:
-    DSAStack->setDefaultDSAPrivate(MLoc);
-    break;
-  default:
-    llvm_unreachable("DSA unexpected in OpenMP default clause");
-  }
-
-  switch (VCKind) {
-  case OMPC_DEFAULT_VC_aggregate:
-    DSAStack->setDefaultDSAVCAggregate(VCKindLoc);
-    break;
-  case OMPC_DEFAULT_VC_all:
-    DSAStack->setDefaultDSAVCAll(VCKindLoc);
-    break;
-  case OMPC_DEFAULT_VC_allocatable:
-    DSAStack->setDefaultDSAVCAllocatable(VCKindLoc);
-    break;
-  case OMPC_DEFAULT_VC_pointer:
-    DSAStack->setDefaultDSAVCPointer(VCKindLoc);
-    break;
-  case OMPC_DEFAULT_VC_scalar:
-    DSAStack->setDefaultDSAVCScalar(VCKindLoc);
-    break;
-  default:
+  if (VCKind == OMPC_DEFAULT_VC_unknown) {
     Diag(VCKindLoc, diag::err_omp_default_vc)
         << getOpenMPSimpleClauseTypeName(OMPC_default, unsigned(M));
+    return nullptr;
   }
 
+  bool IsTargetDefault =
+      getLangOpts().OpenMP >= 60 &&
+      isOpenMPTargetExecutionDirective(DSAStack->getCurrentDirective());
+
+  // OpenMP 6.0, page 224, lines 3-4 default Clause, Semantics
+  // If data-sharing-attribute is shared then the clause has no effect
+  // on a target construct;
+  if (IsTargetDefault && M == OMP_DEFAULT_shared)
+    return nullptr;
+
+  auto SetDefaultClauseAttrs = [&](llvm::omp::DefaultKind M,
+                                   OpenMPDefaultClauseVariableCategory VCKind) {
+    OpenMPDefaultmapClauseModifier DefMapMod;
+    OpenMPDefaultmapClauseKind DefMapKind;
+    // default data-sharing-attribute
+    switch (M) {
+    case OMP_DEFAULT_none:
+      if (IsTargetDefault)
+        DefMapMod = OMPC_DEFAULTMAP_MODIFIER_none;
+      else
+        DSAStack->setDefaultDSANone(MLoc);
+      break;
+    case OMP_DEFAULT_firstprivate:
+      if (IsTargetDefault)
+        DefMapMod = OMPC_DEFAULTMAP_MODIFIER_firstprivate;
+      else
+        DSAStack->setDefaultDSAFirstPrivate(MLoc);
+      break;
+    case OMP_DEFAULT_private:
+      if (IsTargetDefault)
+        DefMapMod = OMPC_DEFAULTMAP_MODIFIER_private;
+      else
+        DSAStack->setDefaultDSAPrivate(MLoc);
+      break;
+    case OMP_DEFAULT_shared:
+      assert(!IsTargetDefault && "DSA shared invalid with target directive");
+      DSAStack->setDefaultDSAShared(MLoc);
+      break;
+    default:
+      llvm_unreachable("unexpected DSA in OpenMP default clause");
+    }
+    // default variable-category
+    switch (VCKind) {
+    case OMPC_DEFAULT_VC_aggregate:
+      if (IsTargetDefault)
+        DefMapKind = OMPC_DEFAULTMAP_aggregate;
+      else
+        DSAStack->setDefaultDSAVCAggregate(VCKindLoc);
+      break;
+    case OMPC_DEFAULT_VC_pointer:
+      if (IsTargetDefault)
+        DefMapKind = OMPC_DEFAULTMAP_pointer;
+      else
+        DSAStack->setDefaultDSAVCPointer(VCKindLoc);
+      break;
+    case OMPC_DEFAULT_VC_scalar:
+      if (IsTargetDefault)
+        DefMapKind = OMPC_DEFAULTMAP_scalar;
+      else
+        DSAStack->setDefaultDSAVCScalar(VCKindLoc);
+      break;
+    case OMPC_DEFAULT_VC_all:
+      if (IsTargetDefault)
+        DefMapKind = OMPC_DEFAULTMAP_all;
+      else
+        DSAStack->setDefaultDSAVCAll(VCKindLoc);
+      break;
+    default:
+      llvm_unreachable("unexpected variable category in OpenMP default clause");
+    }
+    // OpenMP 6.0, page 224, lines 4-5 default Clause, Semantics
+    // otherwise, its effect on a target construct is equivalent to
+    // specifying the defaultmap clause with the same data-sharing-attribute
+    // and variable-category.
+    //
+    // If earlier than OpenMP 6.0, or not a target directive, the default DSA
+    // is/was set as before.
+    if (IsTargetDefault) {
+      if (DefMapKind == OMPC_DEFAULTMAP_all) {
+        DSAStack->setDefaultDMAAttr(DefMapMod, OMPC_DEFAULTMAP_aggregate, MLoc);
+        DSAStack->setDefaultDMAAttr(DefMapMod, OMPC_DEFAULTMAP_scalar, MLoc);
+        DSAStack->setDefaultDMAAttr(DefMapMod, OMPC_DEFAULTMAP_pointer, MLoc);
+      } else {
+        DSAStack->setDefaultDMAAttr(DefMapMod, DefMapKind, MLoc);
+      }
+    }
+  };
+
+  SetDefaultClauseAttrs(M, VCKind);
   return new (getASTContext())
       OMPDefaultClause(M, MLoc, VCKind, VCKindLoc, StartLoc, LParenLoc, EndLoc);
 }