[OpenMP] omp begin/end declare variant - part 1, parsing

This is the first part extracted from D71179 and cleaned up.

This patch provides parsing support for `omp begin/end declare variant`,
as defined in OpenMP technical report 8 (TR8) [0].

A major purpose of this patch is to provide proper math.h/cmath support
for OpenMP target offloading. See PR42061, PR42798, PR42799. The current
code was developed with this feature in mind, see [1].

[0] https://www.openmp.org/wp-content/uploads/openmp-TR8.pdf
[1] https://reviews.llvm.org/D61399#change-496lQkg0mhRN

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D74941

Author: jdoerfert

clang/include/clang/AST/OpenMPClause.h

@@ -7178,9 +7178,11 @@ class OMPTraitInfo {
   /// former is a flat representation the actual main difference is that the
   /// latter uses clang::Expr to store the score/condition while the former is
   /// independent of clang. Thus, expressions and conditions are evaluated in
-  /// this method.
+  /// this method. If \p DeviceSetOnly is true, only the device selector set, if
+  /// present, is put in \p VMI, otherwise all selector sets are put in \p VMI.
   void getAsVariantMatchInfo(ASTContext &ASTCtx,
-                             llvm::omp::VariantMatchInfo &VMI) const;
+                             llvm::omp::VariantMatchInfo &VMI,
+                             bool DeviceSetOnly) const;
 
   /// Print a human readable representation into \p OS.
   void print(llvm::raw_ostream &OS, const PrintingPolicy &Policy) const;

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1232,8 +1232,8 @@ def err_omp_map_type_modifier_missing : Error<
   "missing map type modifier">;
 def err_omp_declare_simd_inbranch_notinbranch : Error<
   "unexpected '%0' clause, '%1' is specified already">;
-def err_expected_end_declare_target : Error<
-  "expected '#pragma omp end declare target'">;
+def err_expected_end_declare_target_or_variant : Error<
+  "expected '#pragma omp end declare %select{target|variant}0'">;
 def err_omp_declare_target_unexpected_clause: Error<
   "unexpected '%0' clause, only %select{'to' or 'link'|'to', 'link' or 'device_type'}1 clauses expected">;
 def err_omp_expected_clause: Error<

clang/include/clang/Parse/Parser.h

@@ -2963,9 +2963,14 @@ class Parser : public CodeCompletionHandler {
   /// Parses OpenMP context selectors.
   bool parseOMPContextSelectors(SourceLocation Loc, OMPTraitInfo &TI);
 
+  /// Parse a `match` clause for an '#pragma omp declare variant'. Return true
+  /// if there was an error.
+  bool parseOMPDeclareVariantMatchClause(SourceLocation Loc, OMPTraitInfo &TI);
+
   /// Parse clauses for '#pragma omp declare variant'.
   void ParseOMPDeclareVariantClauses(DeclGroupPtrTy Ptr, CachedTokens &Toks,
                                      SourceLocation Loc);
+
   /// Parse clauses for '#pragma omp declare target'.
   DeclGroupPtrTy ParseOMPDeclareTargetClauses();
   /// Parse '#pragma omp end declare target'.
@@ -2976,6 +2981,17 @@ class Parser : public CodeCompletionHandler {
   /// it is not the current token.
   void skipUntilPragmaOpenMPEnd(OpenMPDirectiveKind DKind);
 
+  /// Check the \p FoundKind against the \p ExpectedKind, if not issue an error
+  /// that the "end" matching the "begin" directive of kind \p BeginKind was not
+  /// found. Finally, if the expected kind was found or if \p SkipUntilOpenMPEnd
+  /// is set, skip ahead using the helper `skipUntilPragmaOpenMPEnd`.
+  void parseOMPEndDirective(OpenMPDirectiveKind BeginKind,
+                            OpenMPDirectiveKind ExpectedKind,
+                            OpenMPDirectiveKind FoundKind,
+                            SourceLocation MatchingLoc,
+                            SourceLocation FoundLoc,
+                            bool SkipUntilOpenMPEnd);
+
   /// Parses declarative OpenMP directives.
   DeclGroupPtrTy ParseOpenMPDeclarativeDirectiveWithExtDecl(
       AccessSpecifier &AS, ParsedAttributesWithRange &Attrs,

clang/lib/AST/OpenMPClause.cpp

@@ -1868,9 +1868,12 @@ void OMPClausePrinter::VisitOMPExclusiveClause(OMPExclusiveClause *Node) {
   }
 }
 
-void OMPTraitInfo::getAsVariantMatchInfo(
-    ASTContext &ASTCtx, VariantMatchInfo &VMI) const {
+void OMPTraitInfo::getAsVariantMatchInfo(ASTContext &ASTCtx,
+                                         VariantMatchInfo &VMI,
+                                         bool DeviceSetOnly) const {
   for (const OMPTraitSet &Set : Sets) {
+    if (DeviceSetOnly && Set.Kind != TraitSet::device)
+      continue;
     for (const OMPTraitSelector &Selector : Set.Selectors) {
 
       // User conditions are special as we evaluate the condition here.

clang/lib/Basic/OpenMPKinds.cpp

@@ -1025,6 +1025,8 @@ bool clang::isAllowedClauseForDirective(OpenMPDirectiveKind DKind,
       break;
     }
     break;
+  case OMPD_begin_declare_variant:
+  case OMPD_end_declare_variant:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_unknown:
@@ -1288,6 +1290,8 @@ void clang::getOpenMPCaptureRegions(
   case OMPD_end_declare_target:
   case OMPD_requires:
   case OMPD_declare_variant:
+  case OMPD_begin_declare_variant:
+  case OMPD_end_declare_variant:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -7008,6 +7008,8 @@ emitNumTeamsForTargetDirective(CodeGenFunction &CGF,
   case OMPD_target_update:
   case OMPD_declare_simd:
   case OMPD_declare_variant:
+  case OMPD_begin_declare_variant:
+  case OMPD_end_declare_variant:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_declare_reduction:
@@ -7321,6 +7323,8 @@ emitNumThreadsForTargetDirective(CodeGenFunction &CGF,
   case OMPD_target_update:
   case OMPD_declare_simd:
   case OMPD_declare_variant:
+  case OMPD_begin_declare_variant:
+  case OMPD_end_declare_variant:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_declare_reduction:
@@ -9107,6 +9111,8 @@ getNestedDistributeDirective(ASTContext &Ctx, const OMPExecutableDirective &D) {
     case OMPD_target_update:
     case OMPD_declare_simd:
     case OMPD_declare_variant:
+    case OMPD_begin_declare_variant:
+    case OMPD_end_declare_variant:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
@@ -9886,6 +9892,8 @@ void CGOpenMPRuntime::scanForTargetRegionsFunctions(const Stmt *S,
     case OMPD_target_update:
     case OMPD_declare_simd:
     case OMPD_declare_variant:
+    case OMPD_begin_declare_variant:
+    case OMPD_end_declare_variant:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
@@ -10525,6 +10533,8 @@ void CGOpenMPRuntime::emitTargetDataStandAloneCall(
     case OMPD_teams_distribute_parallel_for_simd:
     case OMPD_declare_simd:
     case OMPD_declare_variant:
+    case OMPD_begin_declare_variant:
+    case OMPD_end_declare_variant:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
@@ -11395,7 +11405,8 @@ static const FunctionDecl *getDeclareVariantFunction(CodeGenModule &CGM,
   for (const auto *A : FD->specific_attrs<OMPDeclareVariantAttr>()) {
     const OMPTraitInfo &TI = *A->getTraitInfos();
     VMIs.push_back(VariantMatchInfo());
-    TI.getAsVariantMatchInfo(CGM.getContext(), VMIs.back());
+    TI.getAsVariantMatchInfo(CGM.getContext(), VMIs.back(),
+                             /* DeviceSetOnly */ false);
     VariantExprs.push_back(A->getVariantFuncRef());
   }
 

clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp

@@ -803,6 +803,8 @@ static bool hasNestedSPMDDirective(ASTContext &Ctx,
     case OMPD_target_update:
     case OMPD_declare_simd:
     case OMPD_declare_variant:
+    case OMPD_begin_declare_variant:
+    case OMPD_end_declare_variant:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
@@ -881,6 +883,8 @@ static bool supportsSPMDExecutionMode(ASTContext &Ctx,
   case OMPD_target_update:
   case OMPD_declare_simd:
   case OMPD_declare_variant:
+  case OMPD_begin_declare_variant:
+  case OMPD_end_declare_variant:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_declare_reduction:
@@ -1052,6 +1056,8 @@ static bool hasNestedLightweightDirective(ASTContext &Ctx,
     case OMPD_target_update:
     case OMPD_declare_simd:
     case OMPD_declare_variant:
+    case OMPD_begin_declare_variant:
+    case OMPD_end_declare_variant:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
@@ -1136,6 +1142,8 @@ static bool supportsLightweightRuntime(ASTContext &Ctx,
   case OMPD_target_update:
   case OMPD_declare_simd:
   case OMPD_declare_variant:
+  case OMPD_begin_declare_variant:
+  case OMPD_end_declare_variant:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_declare_reduction: