[flang][OpenMP] Parsing support for iterator modifiers in FROM and TO (#114593)

Parse PRESENT modifier as well while we're at it (no MAPPER though). Add
semantic checks for these clauses in the TARGET UPDATE construct, TODO
messages in lowering.

Author: kparzysz

flang/include/flang/Evaluate/check-expression.h

@@ -115,6 +115,10 @@ extern template std::optional<bool> IsContiguous(
     const CoarrayRef &, FoldingContext &);
 extern template std::optional<bool> IsContiguous(
     const Symbol &, FoldingContext &);
+static inline std::optional<bool> IsContiguous(
+    const SymbolRef &s, FoldingContext &c) {
+  return IsContiguous(s.get(), c);
+}
 template <typename A>
 bool IsSimplyContiguous(const A &x, FoldingContext &context) {
   return IsContiguous(x, context).value_or(false);

flang/include/flang/Parser/dump-parse-tree.h

@@ -525,6 +525,8 @@ class ParseTreeDumper {
   NODE(parser, OmpEndCriticalDirective)
   NODE(parser, OmpEndLoopDirective)
   NODE(parser, OmpEndSectionsDirective)
+  NODE(parser, OmpFromClause)
+  NODE_ENUM(OmpFromClause, Expectation)
   NODE(parser, OmpIfClause)
   NODE_ENUM(OmpIfClause, DirectiveNameModifier)
   NODE_ENUM(OmpLastprivateClause, LastprivateModifier)
@@ -582,6 +584,9 @@ class ParseTreeDumper {
   NODE(parser, OmpSectionBlocks)
   NODE(parser, OmpSectionsDirective)
   NODE(parser, OmpSimpleStandaloneDirective)
+  NODE(parser, OmpToClause)
+  // No NODE_ENUM for OmpToClause::Expectation, because it's an alias
+  // for OmpFromClause::Expectation.
   NODE(parser, Only)
   NODE(parser, OpenACCAtomicConstruct)
   NODE(parser, OpenACCBlockConstruct)

flang/include/flang/Parser/parse-tree.h

@@ -3582,6 +3582,26 @@ struct OmpDeviceTypeClause {
   WRAPPER_CLASS_BOILERPLATE(OmpDeviceTypeClause, Type);
 };
 
+// Ref: [4.5:107-109], [5.0:176-180], [5.1:205-210], [5.2:167-168]
+//
+// from-clause ->
+//    FROM(locator-list) |
+//    FROM(mapper-modifier: locator-list) |             // since 5.0
+//    FROM(motion-modifier[,] ...: locator-list)        // since 5.1
+//  motion-modifier ->
+//    PRESENT | mapper-modifier | iterator-modifier
+struct OmpFromClause {
+  ENUM_CLASS(Expectation, Present);
+  TUPLE_CLASS_BOILERPLATE(OmpFromClause);
+
+  // As in the case of MAP, modifiers are parsed as lists, even if they
+  // are unique. These restrictions will be checked in semantic checks.
+  std::tuple<std::optional<std::list<Expectation>>,
+      std::optional<std::list<OmpIteratorModifier>>, OmpObjectList,
+      bool> // were the modifiers comma-separated?
+      t;
+};
+
 // OMP 5.2 12.6.1 grainsize-clause -> grainsize ([prescriptiveness :] value)
 struct OmpGrainsizeClause {
   TUPLE_CLASS_BOILERPLATE(OmpGrainsizeClause);
@@ -3723,6 +3743,28 @@ struct OmpScheduleClause {
       t;
 };
 
+// Ref: [4.5:107-109], [5.0:176-180], [5.1:205-210], [5.2:167-168]
+//
+// to-clause (in DECLARE TARGET) ->
+//    TO(extended-list) |                               // until 5.1
+// to-clause (in TARGET UPDATE) ->
+//    TO(locator-list) |
+//    TO(mapper-modifier: locator-list) |               // since 5.0
+//    TO(motion-modifier[,] ...: locator-list)          // since 5.1
+//  motion-modifier ->
+//    PRESENT | mapper-modifier | iterator-modifier
+struct OmpToClause {
+  using Expectation = OmpFromClause::Expectation;
+  TUPLE_CLASS_BOILERPLATE(OmpToClause);
+
+  // As in the case of MAP, modifiers are parsed as lists, even if they
+  // are unique. These restrictions will be checked in semantic checks.
+  std::tuple<std::optional<std::list<Expectation>>,
+      std::optional<std::list<OmpIteratorModifier>>, OmpObjectList,
+      bool> // were the modifiers comma-separated?
+      t;
+};
+
 // OMP 5.2 12.6.2 num_tasks-clause -> num_tasks ([prescriptiveness :] value)
 struct OmpNumTasksClause {
   TUPLE_CLASS_BOILERPLATE(OmpNumTasksClause);

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -1019,16 +1019,22 @@ bool ClauseProcessor::processMotionClauses(lower::StatementContext &stmtCtx,
 
   auto callbackFn = [&](const auto &clause, const parser::CharBlock &source) {
     mlir::Location clauseLocation = converter.genLocation(source);
-
+    const auto &[expectation, mapper, iterator, objects] = clause.t;
     // TODO Support motion modifiers: present, mapper, iterator.
+    if (expectation) {
+      TODO(clauseLocation, "PRESENT modifier is not supported yet");
+    } else if (mapper) {
+      TODO(clauseLocation, "Mapper modifier is not supported yet");
+    } else if (iterator) {
+      TODO(clauseLocation, "Iterator modifier is not supported yet");
+    }
     constexpr llvm::omp::OpenMPOffloadMappingFlags mapTypeBits =
         std::is_same_v<llvm::remove_cvref_t<decltype(clause)>, omp::clause::To>
             ? llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_TO
             : llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_FROM;
 
-    processMapObjects(stmtCtx, clauseLocation, std::get<ObjectList>(clause.t),
-                      mapTypeBits, parentMemberIndices, result.mapVars,
-                      mapSymbols);
+    processMapObjects(stmtCtx, clauseLocation, objects, mapTypeBits,
+                      parentMemberIndices, result.mapVars, mapSymbols);
   };
 
   bool clauseFound = findRepeatableClause<omp::clause::To>(callbackFn);

flang/lib/Lower/OpenMP/Clauses.cpp

@@ -728,21 +728,51 @@ Firstprivate make(const parser::OmpClause::Firstprivate &inp,
 
 From make(const parser::OmpClause::From &inp,
           semantics::SemanticsContext &semaCtx) {
-  // inp.v -> parser::OmpObjectList
-  return From{{/*Expectation=*/std::nullopt, /*Mapper=*/std::nullopt,
-               /*Iterator=*/std::nullopt,
-               /*LocatorList=*/makeObjects(inp.v, semaCtx)}};
+  // inp.v -> parser::OmpFromClause
+  using wrapped = parser::OmpFromClause;
+
+  CLAUSET_ENUM_CONVERT( //
+      convert, parser::OmpFromClause::Expectation, From::Expectation,
+      // clang-format off
+      MS(Present, Present)
+      // clang-format on
+  );
+
+  auto &t0 = std::get<std::optional<std::list<wrapped::Expectation>>>(inp.v.t);
+  auto &t1 =
+      std::get<std::optional<std::list<parser::OmpIteratorModifier>>>(inp.v.t);
+  auto &t2 = std::get<parser::OmpObjectList>(inp.v.t);
+
+  assert((!t0 || t0->size() == 1) && "Only one expectation modifier allowed");
+  assert((!t1 || t1->size() == 1) && "Only one iterator modifier allowed");
+
+  auto expectation = [&]() -> std::optional<From::Expectation> {
+    if (t0)
+      return convert(t0->front());
+    return std::nullopt;
+  }();
+
+  auto iterator = [&]() -> std::optional<Iterator> {
+    if (t1)
+      return makeIterator(t1->front(), semaCtx);
+    return std::nullopt;
+  }();
+
+  return From{{/*Expectation=*/std::move(expectation), /*Mapper=*/std::nullopt,
+               /*Iterator=*/std::move(iterator),
+               /*LocatorList=*/makeObjects(t2, semaCtx)}};
 }
 
 // Full: empty
 
 Grainsize make(const parser::OmpClause::Grainsize &inp,
-            semantics::SemanticsContext &semaCtx) {
+               semantics::SemanticsContext &semaCtx) {
   // inp.v -> parser::OmpGrainsizeClause
   using wrapped = parser::OmpGrainsizeClause;
 
   CLAUSET_ENUM_CONVERT( //
-      convert, parser::OmpGrainsizeClause::Prescriptiveness, Grainsize::Prescriptiveness,
+      convert, parser::OmpGrainsizeClause::Prescriptiveness,
+      Grainsize::Prescriptiveness,
       // clang-format off
       MS(Strict,   Strict)
       // clang-format on
@@ -1274,10 +1304,39 @@ ThreadLimit make(const parser::OmpClause::ThreadLimit &inp,
 
 To make(const parser::OmpClause::To &inp,
         semantics::SemanticsContext &semaCtx) {
-  // inp.v -> parser::OmpObjectList
-  return To{{/*Expectation=*/std::nullopt, /*Mapper=*/std::nullopt,
-             /*Iterator=*/std::nullopt,
-             /*LocatorList=*/makeObjects(inp.v, semaCtx)}};
+  // inp.v -> parser::OmpToClause
+  using wrapped = parser::OmpToClause;
+
+  CLAUSET_ENUM_CONVERT( //
+      convert, parser::OmpToClause::Expectation, To::Expectation,
+      // clang-format off
+      MS(Present, Present)
+      // clang-format on
+  );
+
+  auto &t0 = std::get<std::optional<std::list<wrapped::Expectation>>>(inp.v.t);
+  auto &t1 =
+      std::get<std::optional<std::list<parser::OmpIteratorModifier>>>(inp.v.t);
+  auto &t2 = std::get<parser::OmpObjectList>(inp.v.t);
+
+  assert((!t0 || t0->size() == 1) && "Only one expectation modifier allowed");
+  assert((!t1 || t1->size() == 1) && "Only one iterator modifier allowed");
+
+  auto expectation = [&]() -> std::optional<To::Expectation> {
+    if (t0)
+      return convert(t0->front());
+    return std::nullopt;
+  }();
+
+  auto iterator = [&]() -> std::optional<Iterator> {
+    if (t1)
+      return makeIterator(t1->front(), semaCtx);
+    return std::nullopt;
+  }();
+
+  return To{{/*Expectation=*/std::move(expectation), /*Mapper=*/std::nullopt,
+             /*Iterator=*/std::move(iterator),
+             /*LocatorList=*/makeObjects(t2, semaCtx)}};
 }
 
 // UnifiedAddress: empty

flang/lib/Parser/openmp-parsers.cpp

@@ -122,6 +122,40 @@ template <typename Separator> struct MapModifiers {
   const Separator sep_;
 };
 
+// This is almost exactly the same thing as MapModifiers. It has the same
+// issue (it expects modifiers in a specific order), and the fix for that
+// will change how modifiers are parsed. Instead of making this code more
+// generic, make it simple, and generalize after the fix is in place.
+template <typename Separator> struct MotionModifiers {
+  constexpr MotionModifiers(Separator sep) : sep_(sep) {}
+  constexpr MotionModifiers(const MotionModifiers &) = default;
+  constexpr MotionModifiers(MotionModifiers &&) = default;
+
+  // Parsing of mappers if not implemented yet.
+  using ExpParser = Parser<OmpFromClause::Expectation>;
+  using IterParser = Parser<OmpIteratorModifier>;
+  using ModParser = ConcatSeparated<Separator, ExpParser, IterParser>;
+
+  using resultType = typename ModParser::resultType;
+
+  std::optional<resultType> Parse(ParseState &state) const {
+    auto mp{ModParser(sep_, ExpParser{}, IterParser{})};
+    auto mods{mp.Parse(state)};
+    // The ModParser always "succeeds", i.e. even if the input is junk, it
+    // will return a tuple filled with nullopts. If any of the components
+    // is not a nullopt, expect a ":".
+    if (std::apply([](auto &&...opts) { return (... || !!opts); }, *mods)) {
+      if (!attempt(":"_tok).Parse(state)) {
+        return std::nullopt;
+      }
+    }
+    return std::move(mods);
+  }
+
+private:
+  const Separator sep_;
+};
+
 // OpenMP Clauses
 
 // [5.0] 2.1.6 iterator-specifier -> type-declaration-stmt = subscript-triple |
@@ -382,6 +416,31 @@ TYPE_CONTEXT_PARSER("Omp Depend clause"_en_US,
             maybe(Parser<OmpIteratorModifier>{} / ","_tok),
             Parser<OmpTaskDependenceType>{} / ":", Parser<OmpObjectList>{})))
 
+TYPE_PARSER(construct<OmpFromClause::Expectation>(
+    "PRESENT" >> pure(OmpFromClause::Expectation::Present)))
+
+template <typename MotionClause, bool CommasEverywhere>
+static inline MotionClause makeMotionClause(
+    std::tuple<std::optional<std::list<typename MotionClause::Expectation>>,
+        std::optional<std::list<OmpIteratorModifier>>> &&mods,
+    OmpObjectList &&objs) {
+  auto &&[exp, iter] = std::move(mods);
+  return MotionClause(
+      std::move(exp), std::move(iter), std::move(objs), CommasEverywhere);
+}
+
+TYPE_PARSER(construct<OmpFromClause>(
+    applyFunction<OmpFromClause>(makeMotionClause<OmpFromClause, true>,
+        MotionModifiers(","_tok), Parser<OmpObjectList>{}) ||
+    applyFunction<OmpFromClause>(makeMotionClause<OmpFromClause, false>,
+        MotionModifiers(maybe(","_tok)), Parser<OmpObjectList>{})))
+
+TYPE_PARSER(construct<OmpToClause>(
+    applyFunction<OmpToClause>(makeMotionClause<OmpToClause, true>,
+        MotionModifiers(","_tok), Parser<OmpObjectList>{}) ||
+    applyFunction<OmpToClause>(makeMotionClause<OmpToClause, false>,
+        MotionModifiers(maybe(","_tok)), Parser<OmpObjectList>{})))
+
 // 2.15.3.7 LINEAR (linear-list: linear-step)
 //          linear-list -> list | modifier(list)
 //          linear-modifier -> REF | VAL | UVAL
@@ -478,11 +537,11 @@ TYPE_PARSER(
                     parenthesized(scalarIntExpr))) ||
     "FINAL" >> construct<OmpClause>(construct<OmpClause::Final>(
                    parenthesized(scalarLogicalExpr))) ||
-    "FULL" >> construct<OmpClause>(construct<OmpClause::Full>()) ||
     "FIRSTPRIVATE" >> construct<OmpClause>(construct<OmpClause::Firstprivate>(
                           parenthesized(Parser<OmpObjectList>{}))) ||
     "FROM" >> construct<OmpClause>(construct<OmpClause::From>(
-                  parenthesized(Parser<OmpObjectList>{}))) ||
+                  parenthesized(Parser<OmpFromClause>{}))) ||
+    "FULL" >> construct<OmpClause>(construct<OmpClause::Full>()) ||
     "GRAINSIZE" >> construct<OmpClause>(construct<OmpClause::Grainsize>(
                        parenthesized(Parser<OmpGrainsizeClause>{}))) ||
     "HAS_DEVICE_ADDR" >>
@@ -559,7 +618,7 @@ TYPE_PARSER(
     "THREAD_LIMIT" >> construct<OmpClause>(construct<OmpClause::ThreadLimit>(
                           parenthesized(scalarIntExpr))) ||
     "TO" >> construct<OmpClause>(construct<OmpClause::To>(
-                parenthesized(Parser<OmpObjectList>{}))) ||
+                parenthesized(Parser<OmpToClause>{}))) ||
     "USE_DEVICE_PTR" >> construct<OmpClause>(construct<OmpClause::UseDevicePtr>(
                             parenthesized(Parser<OmpObjectList>{}))) ||
     "USE_DEVICE_ADDR" >>

flang/lib/Parser/unparse.cpp

@@ -2138,6 +2138,27 @@ class UnparseVisitor {
     Put(",");
     Walk(std::get<std::optional<ScalarIntConstantExpr>>(x.t));
   }
+  void Unparse(const OmpFromClause &x) {
+    auto &expect{
+        std::get<std::optional<std::list<OmpFromClause::Expectation>>>(x.t)};
+    auto &iter{std::get<std::optional<std::list<OmpIteratorModifier>>>(x.t)};
+    bool needComma{false};
+    if (expect) {
+      Walk(*expect);
+      needComma = true;
+    }
+    if (iter) {
+      if (needComma) {
+        Put(", ");
+      }
+      Walk(*iter);
+      needComma = true;
+    }
+    if (needComma) {
+      Put(": ");
+    }
+    Walk(std::get<OmpObjectList>(x.t));
+  }
   void Unparse(const OmpIfClause &x) {
     Walk(std::get<std::optional<OmpIfClause::DirectiveNameModifier>>(x.t), ":");
     Walk(std::get<ScalarLogicalExpr>(x.t));
@@ -2242,6 +2263,27 @@ class UnparseVisitor {
     Walk(":",
         std::get<std::optional<OmpDefaultmapClause::VariableCategory>>(x.t));
   }
+  void Unparse(const OmpToClause &x) {
+    auto &expect{
+        std::get<std::optional<std::list<OmpToClause::Expectation>>>(x.t)};
+    auto &iter{std::get<std::optional<std::list<OmpIteratorModifier>>>(x.t)};
+    bool needComma{false};
+    if (expect) {
+      Walk(*expect);
+      needComma = true;
+    }
+    if (iter) {
+      if (needComma) {
+        Put(", ");
+      }
+      Walk(*iter);
+      needComma = true;
+    }
+    if (needComma) {
+      Put(": ");
+    }
+    Walk(std::get<OmpObjectList>(x.t));
+  }
 #define GEN_FLANG_CLAUSE_UNPARSE
 #include "llvm/Frontend/OpenMP/OMP.inc"
   void Unparse(const OmpLoopDirective &x) {
@@ -2859,6 +2901,7 @@ class UnparseVisitor {
   WALK_NESTED_ENUM(OmpDeviceTypeClause, Type) // OMP DEVICE_TYPE
   WALK_NESTED_ENUM(
       OmpReductionClause, ReductionModifier) // OMP reduction-modifier
+  WALK_NESTED_ENUM(OmpFromClause, Expectation) // OMP motion-expectation
   WALK_NESTED_ENUM(OmpIfClause, DirectiveNameModifier) // OMP directive-modifier
   WALK_NESTED_ENUM(OmpCancelType, Type) // OMP cancel-type
   WALK_NESTED_ENUM(OmpOrderClause, Type) // OMP order-type