[OpenACC] Implement Sema/AST for 'atomic' construct

The atomic construct is a particularly complicated one.  The directive
itself is pretty simple, it has 5 options for the 'atomic-clause'.
However, the associated statement is fairly complicated.

'read' accepts:
  v = x;
'write' accepts:
  x = expr;
'update' (or no clause) accepts:
  x++;
  x--;
  ++x;
  --x;
  x binop= expr;
  x = x binop expr;
  x = expr binop x;

'capture' accepts either a compound statement, or:
  v = x++;
  v = x--;
  v = ++x;
  v = --x;
  v = x binop= expr;
  v = x = x binop expr;
  v = x = expr binop x;

IF 'capture' has a compound statement, it accepts:
  {v = x; x binop= expr; }
  {x binop= expr; v = x; }
  {v = x; x = x binop expr; }
  {v = x; x = expr binop x; }
  {x = x binop expr ;v = x; }
  {x = expr binop x; v = x; }
  {v = x; x = expr; }
  {v = x; x++; }
  {v = x; ++x; }
  {x++; v = x; }
  {++x; v = x; }
  {v = x; x--; }
  {v = x; --x; }
  {x--; v = x; }
  {--x; v = x; }

While these are all quite complicated, there is a significant amount
of similarity between the 'capture' and 'update' lists, so this patch
reuses a lot of the same functions.

This patch implements the entirety of 'atomic', creating a new Sema file
for the sema for it, as it is fairly sizable.

Author: erichkeane

clang/include/clang-c/Index.h

@@ -2206,7 +2206,11 @@ enum CXCursorKind {
    */
   CXCursor_OpenACCUpdateConstruct = 331,
 
-  CXCursor_LastStmt = CXCursor_OpenACCUpdateConstruct,
+  /** OpenACC atomic Construct.
+   */
+  CXCursor_OpenACCAtomicConstruct = 332,
+
+  CXCursor_LastStmt = CXCursor_OpenACCAtomicConstruct,
 
   /**
    * Cursor that represents the translation unit itself.

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -4099,6 +4099,8 @@ DEF_TRAVERSE_STMT(OpenACCSetConstruct,
                   { TRY_TO(VisitOpenACCClauseList(S->clauses())); })
 DEF_TRAVERSE_STMT(OpenACCUpdateConstruct,
                   { TRY_TO(VisitOpenACCClauseList(S->clauses())); })
+DEF_TRAVERSE_STMT(OpenACCAtomicConstruct,
+                  { TRY_TO(TraverseOpenACCAssociatedStmtConstruct(S)); })
 
 // Traverse HLSL: Out argument expression
 DEF_TRAVERSE_STMT(HLSLOutArgExpr, {})

clang/include/clang/AST/StmtOpenACC.h

@@ -751,5 +751,50 @@ class OpenACCUpdateConstruct final
   Create(const ASTContext &C, SourceLocation Start, SourceLocation DirectiveLoc,
          SourceLocation End, ArrayRef<const OpenACCClause *> Clauses);
 };
+
+// This class represents the 'atomic' construct, which has an associated
+// statement, but no clauses.
+class OpenACCAtomicConstruct final : public OpenACCAssociatedStmtConstruct {
+
+  friend class ASTStmtReader;
+  OpenACCAtomicKind AtomicKind = OpenACCAtomicKind::None;
+
+  OpenACCAtomicConstruct(EmptyShell)
+      : OpenACCAssociatedStmtConstruct(
+            OpenACCAtomicConstructClass, OpenACCDirectiveKind::Atomic,
+            SourceLocation{}, SourceLocation{}, SourceLocation{},
+            /*AssociatedStmt=*/nullptr) {}
+
+  OpenACCAtomicConstruct(SourceLocation Start, SourceLocation DirectiveLoc,
+                         OpenACCAtomicKind AtKind, SourceLocation End,
+                         Stmt *AssociatedStmt)
+      : OpenACCAssociatedStmtConstruct(OpenACCAtomicConstructClass,
+                                       OpenACCDirectiveKind::Atomic, Start,
+                                       DirectiveLoc, End, AssociatedStmt),
+        AtomicKind(AtKind) {}
+
+  void setAssociatedStmt(Stmt *S) {
+    OpenACCAssociatedStmtConstruct::setAssociatedStmt(S);
+  }
+
+public:
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() == OpenACCAtomicConstructClass;
+  }
+
+  static OpenACCAtomicConstruct *CreateEmpty(const ASTContext &C);
+  static OpenACCAtomicConstruct *
+  Create(const ASTContext &C, SourceLocation Start, SourceLocation DirectiveLoc,
+         OpenACCAtomicKind AtKind, SourceLocation End, Stmt *AssociatedStmt);
+
+  OpenACCAtomicKind getAtomicKind() const { return AtomicKind; }
+  const Stmt *getAssociatedStmt() const {
+    return OpenACCAssociatedStmtConstruct::getAssociatedStmt();
+  }
+  Stmt *getAssociatedStmt() {
+    return OpenACCAssociatedStmtConstruct::getAssociatedStmt();
+  }
+};
+
 } // namespace clang
 #endif // LLVM_CLANG_AST_STMTOPENACC_H

clang/include/clang/AST/TextNodeDumper.h

@@ -420,6 +420,7 @@ class TextNodeDumper
   void VisitOpenACCSetConstruct(const OpenACCSetConstruct *S);
   void VisitOpenACCShutdownConstruct(const OpenACCShutdownConstruct *S);
   void VisitOpenACCUpdateConstruct(const OpenACCUpdateConstruct *S);
+  void VisitOpenACCAtomicConstruct(const OpenACCAtomicConstruct *S);
   void VisitOpenACCAsteriskSizeExpr(const OpenACCAsteriskSizeExpr *S);
   void VisitEmbedExpr(const EmbedExpr *S);
   void VisitAtomicExpr(const AtomicExpr *AE);

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -12903,6 +12903,48 @@ def err_acc_update_as_body
     : Error<"OpenACC 'update' construct may not appear in place of the "
             "statement following a%select{n if statement| while statement| do "
             "statement| switch statement| label statement}0">;
+def err_acc_invalid_atomic
+    : Error<"statement associated with OpenACC 'atomic%select{| "
+            "%1}0' directive is invalid">;
+def note_acc_atomic_expr_must_be
+    : Note<"expected "
+           "%enum_select<OACCAtomicExpr>{%Assign{assignment}|%UnaryCompAssign{"
+           "assignment, compound assignment, increment, or decrement}}0 "
+           "expression">;
+def note_acc_atomic_unsupported_unary_operator
+    : Note<"unary operator not supported, only increment and decrement "
+           "operations permitted">;
+def note_acc_atomic_unsupported_binary_operator
+    : Note<"binary operator not supported, only +, *, -, /, &, ^, |, <<, or >> "
+           "are permitted">;
+def note_acc_atomic_unsupported_compound_binary_operator
+    : Note<"compound binary operator not supported, only +=, *=, -=, /=, &=, "
+           "^=, |=, <<=, or >>= are permitted">;
+
+def note_acc_atomic_operand_lvalue_scalar
+    : Note<"%select{left |right |}0operand to "
+           "%enum_select<OACCAtomicOpKind>{%Assign{assignment}|%CompoundAssign{"
+           "compound assignment}|%Inc{increment}|"
+           "%Dec{decrement}}1 "
+           "expression must be "
+           "%enum_select<OACCLValScalar>{%LVal{an l-value}|%Scalar{of scalar "
+           "type (was %3)}}2">;
+def note_acc_atomic_too_many_stmts
+    : Note<"'atomic capture' with a compound statement only supports two "
+           "statements">;
+def note_acc_atomic_expected_binop : Note<"expected binary operation on right "
+                                          "hand side of assignment operator">;
+def note_acc_atomic_mismatch_operand
+    : Note<"left hand side of assignment operation('%0') must match one side "
+           "of the sub-operation on the right hand side('%1' and '%2')">;
+def note_acc_atomic_mismatch_compound_operand
+    : Note<"variable %select{|in unary expression|on right hand side of "
+           "assignment|on left hand side of assignment|on left hand side of "
+           "compound assignment|on left hand side of assignment}2('%3') must "
+           "match variable used %select{|in unary expression|on right hand "
+           "side of assignment|<not possible>|on left hand side of compound "
+           "assignment|on left hand side of assignment}0('%1') from the first "
+           "statement">;
 
 // AMDGCN builtins diagnostics
 def err_amdgcn_global_load_lds_size_invalid_value : Error<"invalid size value">;

clang/include/clang/Basic/OpenACCKinds.h

@@ -171,9 +171,33 @@ enum class OpenACCAtomicKind : uint8_t {
   Write,
   Update,
   Capture,
-  Invalid,
+  None,
 };
 
+template <typename StreamTy>
+inline StreamTy &printOpenACCAtomicKind(StreamTy &Out, OpenACCAtomicKind AK) {
+  switch (AK) {
+  case OpenACCAtomicKind::Read:
+    return Out << "read";
+  case OpenACCAtomicKind::Write:
+    return Out << "write";
+  case OpenACCAtomicKind::Update:
+    return Out << "update";
+  case OpenACCAtomicKind::Capture:
+    return Out << "capture";
+  case OpenACCAtomicKind::None:
+    return Out << "<none>";
+  }
+}
+inline const StreamingDiagnostic &operator<<(const StreamingDiagnostic &Out,
+                                             OpenACCAtomicKind AK) {
+  return printOpenACCAtomicKind(Out, AK);
+}
+inline llvm::raw_ostream &operator<<(llvm::raw_ostream &Out,
+                                     OpenACCAtomicKind AK) {
+  return printOpenACCAtomicKind(Out, AK);
+}
+
 /// Represents the kind of an OpenACC clause.
 enum class OpenACCClauseKind : uint8_t {
   /// 'finalize' clause, allowed on 'exit data' directive.

clang/include/clang/Basic/StmtNodes.td

@@ -319,6 +319,7 @@ def OpenACCInitConstruct : StmtNode<OpenACCConstructStmt>;
 def OpenACCShutdownConstruct : StmtNode<OpenACCConstructStmt>;
 def OpenACCSetConstruct : StmtNode<OpenACCConstructStmt>;
 def OpenACCUpdateConstruct : StmtNode<OpenACCConstructStmt>;
+def OpenACCAtomicConstruct : StmtNode<OpenACCAssociatedStmtConstruct>;
 
 // OpenACC Additional Expressions.
 def OpenACCAsteriskSizeExpr : StmtNode<Expr>;

clang/include/clang/Parse/Parser.h

@@ -3710,6 +3710,7 @@ class Parser : public CodeCompletionHandler {
     SourceLocation RParenLoc;
     SourceLocation EndLoc;
     SourceLocation MiscLoc;
+    OpenACCAtomicKind AtomicKind;
     SmallVector<Expr *> Exprs;
     SmallVector<OpenACCClause *> Clauses;
     // TODO OpenACC: As we implement support for the Atomic, Routine, and Cache

clang/include/clang/Sema/SemaOpenACC.h

@@ -695,24 +695,53 @@ class SemaOpenACC : public SemaBase {
   /// should check legality of the statement as it appertains to this Construct.
   StmtResult ActOnAssociatedStmt(SourceLocation DirectiveLoc,
                                  OpenACCDirectiveKind K,
+                                 OpenACCAtomicKind AtKind,
                                  ArrayRef<const OpenACCClause *> Clauses,
                                  StmtResult AssocStmt);
 
+  StmtResult ActOnAssociatedStmt(SourceLocation DirectiveLoc,
+                                 OpenACCDirectiveKind K,
+                                 ArrayRef<const OpenACCClause *> Clauses,
+                                 StmtResult AssocStmt) {
+    return ActOnAssociatedStmt(DirectiveLoc, K, OpenACCAtomicKind::None,
+                               Clauses, AssocStmt);
+  }
+  /// Called to check the form of the `atomic` construct which has some fairly
+  /// sizable restrictions.
+  StmtResult CheckAtomicAssociatedStmt(SourceLocation AtomicDirLoc,
+                                       OpenACCAtomicKind AtKind,
+                                       StmtResult AssocStmt);
+
   /// Called after the directive has been completely parsed, including the
   /// declaration group or associated statement.
+  /// DirLoc: Location of the actual directive keyword.
   /// LParenLoc: Location of the left paren, if it exists (not on all
   /// constructs).
   /// MiscLoc: First misc location, if necessary (not all constructs).
   /// Exprs: List of expressions on the construct itself, if necessary (not all
   /// constructs).
+  /// AK: The atomic kind of the directive, if necessary (atomic only)
   /// RParenLoc: Location of the right paren, if it exists (not on all
   /// constructs).
+  /// EndLoc: The last source location of the driective.
+  /// Clauses: The list of clauses for the directive, if present.
+  /// AssocStmt: The associated statement for this construct, if necessary.
   StmtResult ActOnEndStmtDirective(
       OpenACCDirectiveKind K, SourceLocation StartLoc, SourceLocation DirLoc,
       SourceLocation LParenLoc, SourceLocation MiscLoc, ArrayRef<Expr *> Exprs,
-      SourceLocation RParenLoc, SourceLocation EndLoc,
+      OpenACCAtomicKind AK, SourceLocation RParenLoc, SourceLocation EndLoc,
       ArrayRef<OpenACCClause *> Clauses, StmtResult AssocStmt);
 
+  StmtResult ActOnEndStmtDirective(
+      OpenACCDirectiveKind K, SourceLocation StartLoc, SourceLocation DirLoc,
+      SourceLocation LParenLoc, SourceLocation MiscLoc, ArrayRef<Expr *> Exprs,
+      SourceLocation RParenLoc, SourceLocation EndLoc,
+      ArrayRef<OpenACCClause *> Clauses, StmtResult AssocStmt) {
+    return ActOnEndStmtDirective(K, StartLoc, DirLoc, LParenLoc, MiscLoc, Exprs,
+                                 OpenACCAtomicKind::None, RParenLoc, EndLoc,
+                                 Clauses, AssocStmt);
+  }
+
   /// Called after the directive has been completely parsed, including the
   /// declaration group or associated statement.
   DeclGroupRef ActOnEndDeclDirective();

clang/include/clang/Serialization/ASTBitCodes.h

@@ -2045,6 +2045,7 @@ enum StmtCode {
   STMT_OPENACC_SHUTDOWN_CONSTRUCT,
   STMT_OPENACC_SET_CONSTRUCT,
   STMT_OPENACC_UPDATE_CONSTRUCT,
+  STMT_OPENACC_ATOMIC_CONSTRUCT,
 
   // HLSL Constructs
   EXPR_HLSL_OUT_ARG,