[OpenACC] Implement loop restrictions on for loops.

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -12735,6 +12735,19 @@ def err_acc_gang_reduction_numgangs_conflict
 def err_reduction_op_mismatch
     : Error<"OpenACC 'reduction' variable must have the same operator in all "
             "nested constructs (%0 vs %1)">;
+def err_acc_loop_variable_type
+    : Error<"loop variable of loop associated with an OpenACC 'loop' construct "
+            "must be of integer, pointer, or random-access-iterator type (is "
+            "%0)">;
+def err_acc_loop_variable
+    : Error<"OpenACC 'loop' construct must have initialization clause in "
+            "canonical form ('var = init' or 'T var = init')">;
+def err_acc_loop_terminating_condition
+    : Error<"OpenACC 'loop' construct must have a terminating condition">;
+def err_acc_loop_not_monotonic
+    : Error<"OpenACC 'loop' variable must monotonically increase or decrease "
+            "('++', '--', or compound assignment)">;
+
 // AMDGCN builtins diagnostics
 def err_amdgcn_global_load_lds_size_invalid_value : Error<"invalid size value">;
 def note_amdgcn_global_load_lds_size_valid_value : Note<"size must be 1, 2, or 4">;

clang/include/clang/Sema/SemaOpenACC.h

@@ -118,6 +118,43 @@ class SemaOpenACC : public SemaBase {
   /// 'loop' clause enforcement, where this is 'blocked' by a compute construct.
   llvm::SmallVector<OpenACCReductionClause *> ActiveReductionClauses;
 
+  // Type to check the info about the 'for stmt'.
+  struct ForStmtBeginChecker {
+    SemaOpenACC &SemaRef;
+    SourceLocation ForLoc;
+    bool IsRangeFor = false;
+    std::optional<const CXXForRangeStmt *> RangeFor = nullptr;
+    const Stmt *Init = nullptr;
+    bool InitChanged = false;
+    std::optional<const Stmt *> Cond = nullptr;
+    std::optional<const Stmt *> Inc = nullptr;
+    // Prevent us from checking 2x, which can happen with collapse & tile.
+    bool AlreadyChecked = false;
+
+    ForStmtBeginChecker(SemaOpenACC &SemaRef, SourceLocation ForLoc,
+                        std::optional<const CXXForRangeStmt *> S)
+        : SemaRef(SemaRef), ForLoc(ForLoc), IsRangeFor(true), RangeFor(S) {}
+
+    ForStmtBeginChecker(SemaOpenACC &SemaRef, SourceLocation ForLoc,
+                        const Stmt *I, bool InitChanged,
+                        std::optional<const Stmt *> C,
+                        std::optional<const Stmt *> Inc)
+        : SemaRef(SemaRef), ForLoc(ForLoc), IsRangeFor(false), Init(I),
+          InitChanged(InitChanged), Cond(C), Inc(Inc) {}
+    // Do the checking for the For/Range-For. Currently this implements the 'not
+    // seq' restrictions only, and should be called either if we know we are a
+    // top-level 'for' (the one associated via associated-stmt), or extended via
+    // 'collapse'.
+    void check();
+
+    const ValueDecl *checkInit();
+    void checkCond();
+    void checkInc(const ValueDecl *Init);
+  };
+
+  /// Helper function for checking the 'for' and 'range for' stmts.
+  void ForStmtBeginHelper(SourceLocation ForLoc, ForStmtBeginChecker &C);
+
 public:
   ComputeConstructInfo &getActiveComputeConstructInfo() {
     return ActiveComputeConstructInfo;
@@ -137,6 +174,11 @@ class SemaOpenACC : public SemaBase {
   /// permits us to implement the restriction of no further 'gang', 'vector', or
   /// 'worker' clauses.
   SourceLocation LoopVectorClauseLoc;
+  /// If there is a current 'active' loop construct that does NOT have a 'seq'
+  /// clause on it, this has that source location. This permits us to implement
+  /// the 'loop' restrictions on the loop variable. This can be extended via
+  /// 'collapse', so we need to keep this around for a while.
+  SourceLocation LoopWithoutSeqLoc;
 
   // Redeclaration of the version in OpenACCClause.h.
   using DeviceTypeArgument = std::pair<IdentifierInfo *, SourceLocation>;
@@ -568,8 +610,19 @@ class SemaOpenACC : public SemaBase {
   void ActOnWhileStmt(SourceLocation WhileLoc);
   // Called when we encounter a 'do' statement, before looking at its 'body'.
   void ActOnDoStmt(SourceLocation DoLoc);
+  // Called when we encounter a 'for' statement, before looking at its 'body',
+  // for the 'range-for'. 'ActOnForStmtEnd' is used after the body.
+  void ActOnRangeForStmtBegin(SourceLocation ForLoc, const Stmt *OldRangeFor,
+                              const Stmt *RangeFor);
+  void ActOnRangeForStmtBegin(SourceLocation ForLoc, const Stmt *RangeFor);
   // Called when we encounter a 'for' statement, before looking at its 'body'.
-  void ActOnForStmtBegin(SourceLocation ForLoc);
+  // 'ActOnForStmtEnd' is used after the body.
+  void ActOnForStmtBegin(SourceLocation ForLoc, const Stmt *First,
+                         const Stmt *Second, const Stmt *Third);
+  void ActOnForStmtBegin(SourceLocation ForLoc, const Stmt *OldFirst,
+                         const Stmt *First, const Stmt *OldSecond,
+                         const Stmt *Second, const Stmt *OldThird,
+                         const Stmt *Third);
   // Called when we encounter a 'for' statement, after we've consumed/checked
   // the body. This is necessary for a number of checks on the contents of the
   // 'for' statement.
@@ -598,7 +651,9 @@ class SemaOpenACC : public SemaBase {
   /// Called when we encounter an associated statement for our construct, this
   /// should check legality of the statement as it appertains to this Construct.
   StmtResult ActOnAssociatedStmt(SourceLocation DirectiveLoc,
-                                 OpenACCDirectiveKind K, StmtResult AssocStmt);
+                                 OpenACCDirectiveKind K,
+                                 ArrayRef<const OpenACCClause *> Clauses,
+                                 StmtResult AssocStmt);
 
   /// Called after the directive has been completely parsed, including the
   /// declaration group or associated statement.
@@ -712,12 +767,13 @@ class SemaOpenACC : public SemaBase {
     SourceLocation OldLoopGangClauseOnKernelLoc;
     SourceLocation OldLoopWorkerClauseLoc;
     SourceLocation OldLoopVectorClauseLoc;
+    SourceLocation OldLoopWithoutSeqLoc;
     llvm::SmallVector<OpenACCLoopConstruct *> ParentlessLoopConstructs;
     llvm::SmallVector<OpenACCReductionClause *> ActiveReductionClauses;
     LoopInConstructRAII LoopRAII;
 
   public:
-    AssociatedStmtRAII(SemaOpenACC &, OpenACCDirectiveKind,
+    AssociatedStmtRAII(SemaOpenACC &, OpenACCDirectiveKind, SourceLocation,
                        ArrayRef<const OpenACCClause *>,
                        ArrayRef<OpenACCClause *>);
     void SetCollapseInfoBeforeAssociatedStmt(

clang/lib/Parse/ParseOpenACC.cpp

@@ -1498,14 +1498,15 @@ StmtResult Parser::ParseOpenACCDirectiveStmt() {
     return StmtError();
 
   StmtResult AssocStmt;
-  SemaOpenACC::AssociatedStmtRAII AssocStmtRAII(
-      getActions().OpenACC(), DirInfo.DirKind, {}, DirInfo.Clauses);
+  SemaOpenACC::AssociatedStmtRAII AssocStmtRAII(getActions().OpenACC(),
+                                                DirInfo.DirKind, DirInfo.DirLoc,
+                                                {}, DirInfo.Clauses);
   if (doesDirectiveHaveAssociatedStmt(DirInfo.DirKind)) {
     ParsingOpenACCDirectiveRAII DirScope(*this, /*Value=*/false);
     ParseScope ACCScope(this, getOpenACCScopeFlags(DirInfo.DirKind));
 
     AssocStmt = getActions().OpenACC().ActOnAssociatedStmt(
-        DirInfo.StartLoc, DirInfo.DirKind, ParseStatement());
+        DirInfo.StartLoc, DirInfo.DirKind, DirInfo.Clauses, ParseStatement());
   }
 
   return getActions().OpenACC().ActOnEndStmtDirective(

clang/lib/Parse/ParseStmt.cpp

@@ -2360,7 +2360,11 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
   // OpenACC Restricts a for-loop inside of certain construct/clause
   // combinations, so diagnose that here in OpenACC mode.
   SemaOpenACC::LoopInConstructRAII LCR{getActions().OpenACC()};
-  getActions().OpenACC().ActOnForStmtBegin(ForLoc);
+  if (ForRangeInfo.ParsedForRangeDecl())
+    getActions().OpenACC().ActOnRangeForStmtBegin(ForLoc, ForRangeStmt.get());
+  else
+    getActions().OpenACC().ActOnForStmtBegin(
+        ForLoc, FirstPart.get(), SecondPart.get().second, ThirdPart.get());
 
   // C99 6.8.5p5 - In C99, the body of the for statement is a scope, even if
   // there is no compound stmt.  C90 does not have this clause.  We only do this