[NFC][flang][OpenMP] Split DataSharing and Clause processors (#81973)

This started as an experiment to reduce the compilation time of
iterating over `Lower/OpenMP.cpp` a bit since it is too slow at the
moment. Trying to do that, I split the `DataSharingProcessor`,
`ReductionProcessor`, and `ClauseProcessor` into their own files and
extracted some shared code into a util file. All of these new `.h/.cpp`
files as well as `OpenMP.cpp` are now under a `Lower/OpenMP/` directory.

This resulted is a slightly better organization of the OpenMP lowering
code and hence opening this NFC.

As for the compilation time, this unfortunately does not affect it much
(it shaves off a few seconds of `OpenMP.cpp` compilation) since from
what I learned the bottleneck is in `DirectivesCommon.h` and
`PFTBuilder.h` which both consume a lot of time in template
instantiation it seems.

Author: ergawy

flang/lib/Lower/CMakeLists.txt

@@ -24,7 +24,11 @@ add_flang_library(FortranLower
   LoweringOptions.cpp
   Mangler.cpp
   OpenACC.cpp
-  OpenMP.cpp
+  OpenMP/ClauseProcessor.cpp
+  OpenMP/DataSharingProcessor.cpp
+  OpenMP/OpenMP.cpp
+  OpenMP/ReductionProcessor.cpp
+  OpenMP/Utils.cpp
   PFTBuilder.cpp
   Runtime.cpp
   SymbolMap.cpp

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -0,0 +1,305 @@
+//===-- Lower/OpenMP/ClauseProcessor.h --------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Coding style: https://mlir.llvm.org/getting_started/DeveloperGuide/
+//
+//===----------------------------------------------------------------------===//
+#ifndef FORTRAN_LOWER_CLAUASEPROCESSOR_H
+#define FORTRAN_LOWER_CLAUASEPROCESSOR_H
+
+#include "DirectivesCommon.h"
+#include "ReductionProcessor.h"
+#include "Utils.h"
+#include "flang/Lower/AbstractConverter.h"
+#include "flang/Lower/Bridge.h"
+#include "flang/Optimizer/Builder/Todo.h"
+#include "flang/Parser/dump-parse-tree.h"
+#include "flang/Parser/parse-tree.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
+
+namespace fir {
+class FirOpBuilder;
+} // namespace fir
+
+namespace Fortran {
+namespace lower {
+namespace omp {
+
+/// Class that handles the processing of OpenMP clauses.
+///
+/// Its `process<ClauseName>()` methods perform MLIR code generation for their
+/// corresponding clause if it is present in the clause list. Otherwise, they
+/// will return `false` to signal that the clause was not found.
+///
+/// The intended use is of this class is to move clause processing outside of
+/// construct processing, since the same clauses can appear attached to
+/// different constructs and constructs can be combined, so that code
+/// duplication is minimized.
+///
+/// Each construct-lowering function only calls the `process<ClauseName>()`
+/// methods that relate to clauses that can impact the lowering of that
+/// construct.
+class ClauseProcessor {
+  using ClauseTy = Fortran::parser::OmpClause;
+
+public:
+  ClauseProcessor(Fortran::lower::AbstractConverter &converter,
+                  Fortran::semantics::SemanticsContext &semaCtx,
+                  const Fortran::parser::OmpClauseList &clauses)
+      : converter(converter), semaCtx(semaCtx), clauses(clauses) {}
+
+  // 'Unique' clauses: They can appear at most once in the clause list.
+  bool
+  processCollapse(mlir::Location currentLocation,
+                  Fortran::lower::pft::Evaluation &eval,
+                  llvm::SmallVectorImpl<mlir::Value> &lowerBound,
+                  llvm::SmallVectorImpl<mlir::Value> &upperBound,
+                  llvm::SmallVectorImpl<mlir::Value> &step,
+                  llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> &iv,
+                  std::size_t &loopVarTypeSize) const;
+  bool processDefault() const;
+  bool processDevice(Fortran::lower::StatementContext &stmtCtx,
+                     mlir::Value &result) const;
+  bool processDeviceType(mlir::omp::DeclareTargetDeviceType &result) const;
+  bool processFinal(Fortran::lower::StatementContext &stmtCtx,
+                    mlir::Value &result) const;
+  bool processHint(mlir::IntegerAttr &result) const;
+  bool processMergeable(mlir::UnitAttr &result) const;
+  bool processNowait(mlir::UnitAttr &result) const;
+  bool processNumTeams(Fortran::lower::StatementContext &stmtCtx,
+                       mlir::Value &result) const;
+  bool processNumThreads(Fortran::lower::StatementContext &stmtCtx,
+                         mlir::Value &result) const;
+  bool processOrdered(mlir::IntegerAttr &result) const;
+  bool processPriority(Fortran::lower::StatementContext &stmtCtx,
+                       mlir::Value &result) const;
+  bool processProcBind(mlir::omp::ClauseProcBindKindAttr &result) const;
+  bool processSafelen(mlir::IntegerAttr &result) const;
+  bool processSchedule(mlir::omp::ClauseScheduleKindAttr &valAttr,
+                       mlir::omp::ScheduleModifierAttr &modifierAttr,
+                       mlir::UnitAttr &simdModifierAttr) const;
+  bool processScheduleChunk(Fortran::lower::StatementContext &stmtCtx,
+                            mlir::Value &result) const;
+  bool processSimdlen(mlir::IntegerAttr &result) const;
+  bool processThreadLimit(Fortran::lower::StatementContext &stmtCtx,
+                          mlir::Value &result) const;
+  bool processUntied(mlir::UnitAttr &result) const;
+
+  // 'Repeatable' clauses: They can appear multiple times in the clause list.
+  bool
+  processAllocate(llvm::SmallVectorImpl<mlir::Value> &allocatorOperands,
+                  llvm::SmallVectorImpl<mlir::Value> &allocateOperands) const;
+  bool processCopyin() const;
+  bool processDepend(llvm::SmallVectorImpl<mlir::Attribute> &dependTypeOperands,
+                     llvm::SmallVectorImpl<mlir::Value> &dependOperands) const;
+  bool
+  processEnter(llvm::SmallVectorImpl<DeclareTargetCapturePair> &result) const;
+  bool
+  processIf(Fortran::parser::OmpIfClause::DirectiveNameModifier directiveName,
+            mlir::Value &result) const;
+  bool
+  processLink(llvm::SmallVectorImpl<DeclareTargetCapturePair> &result) const;
+
+  // This method is used to process a map clause.
+  // The optional parameters - mapSymTypes, mapSymLocs & mapSymbols are used to
+  // store the original type, location and Fortran symbol for the map operands.
+  // They may be used later on to create the block_arguments for some of the
+  // target directives that require it.
+  bool processMap(mlir::Location currentLocation,
+                  const llvm::omp::Directive &directive,
+                  Fortran::lower::StatementContext &stmtCtx,
+                  llvm::SmallVectorImpl<mlir::Value> &mapOperands,
+                  llvm::SmallVectorImpl<mlir::Type> *mapSymTypes = nullptr,
+                  llvm::SmallVectorImpl<mlir::Location> *mapSymLocs = nullptr,
+                  llvm::SmallVectorImpl<const Fortran::semantics::Symbol *>
+                      *mapSymbols = nullptr) const;
+  bool
+  processReduction(mlir::Location currentLocation,
+                   llvm::SmallVectorImpl<mlir::Value> &reductionVars,
+                   llvm::SmallVectorImpl<mlir::Attribute> &reductionDeclSymbols,
+                   llvm::SmallVectorImpl<const Fortran::semantics::Symbol *>
+                       *reductionSymbols = nullptr) const;
+  bool processSectionsReduction(mlir::Location currentLocation) const;
+  bool processTo(llvm::SmallVectorImpl<DeclareTargetCapturePair> &result) const;
+  bool
+  processUseDeviceAddr(llvm::SmallVectorImpl<mlir::Value> &operands,
+                       llvm::SmallVectorImpl<mlir::Type> &useDeviceTypes,
+                       llvm::SmallVectorImpl<mlir::Location> &useDeviceLocs,
+                       llvm::SmallVectorImpl<const Fortran::semantics::Symbol *>
+                           &useDeviceSymbols) const;
+  bool
+  processUseDevicePtr(llvm::SmallVectorImpl<mlir::Value> &operands,
+                      llvm::SmallVectorImpl<mlir::Type> &useDeviceTypes,
+                      llvm::SmallVectorImpl<mlir::Location> &useDeviceLocs,
+                      llvm::SmallVectorImpl<const Fortran::semantics::Symbol *>
+                          &useDeviceSymbols) const;
+
+  template <typename T>
+  bool processMotionClauses(Fortran::lower::StatementContext &stmtCtx,
+                            llvm::SmallVectorImpl<mlir::Value> &mapOperands);
+
+  // Call this method for these clauses that should be supported but are not
+  // implemented yet. It triggers a compilation error if any of the given
+  // clauses is found.
+  template <typename... Ts>
+  void processTODO(mlir::Location currentLocation,
+                   llvm::omp::Directive directive) const;
+
+private:
+  using ClauseIterator = std::list<ClauseTy>::const_iterator;
+
+  /// Utility to find a clause within a range in the clause list.
+  template <typename T>
+  static ClauseIterator findClause(ClauseIterator begin, ClauseIterator end);
+
+  /// Return the first instance of the given clause found in the clause list or
+  /// `nullptr` if not present. If more than one instance is expected, use
+  /// `findRepeatableClause` instead.
+  template <typename T>
+  const T *
+  findUniqueClause(const Fortran::parser::CharBlock **source = nullptr) const;
+
+  /// Call `callbackFn` for each occurrence of the given clause. Return `true`
+  /// if at least one instance was found.
+  template <typename T>
+  bool findRepeatableClause(
+      std::function<void(const T *, const Fortran::parser::CharBlock &source)>
+          callbackFn) const;
+
+  /// Set the `result` to a new `mlir::UnitAttr` if the clause is present.
+  template <typename T>
+  bool markClauseOccurrence(mlir::UnitAttr &result) const;
+
+  Fortran::lower::AbstractConverter &converter;
+  Fortran::semantics::SemanticsContext &semaCtx;
+  const Fortran::parser::OmpClauseList &clauses;
+};
+
+template <typename T>
+bool ClauseProcessor::processMotionClauses(
+    Fortran::lower::StatementContext &stmtCtx,
+    llvm::SmallVectorImpl<mlir::Value> &mapOperands) {
+  return findRepeatableClause<T>(
+      [&](const T *motionClause, const Fortran::parser::CharBlock &source) {
+        mlir::Location clauseLocation = converter.genLocation(source);
+        fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
+
+        static_assert(std::is_same_v<T, ClauseProcessor::ClauseTy::To> ||
+                      std::is_same_v<T, ClauseProcessor::ClauseTy::From>);
+
+        // TODO Support motion modifiers: present, mapper, iterator.
+        constexpr llvm::omp::OpenMPOffloadMappingFlags mapTypeBits =
+            std::is_same_v<T, ClauseProcessor::ClauseTy::To>
+                ? llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_TO
+                : llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_FROM;
+
+        for (const Fortran::parser::OmpObject &ompObject : motionClause->v.v) {
+          llvm::SmallVector<mlir::Value> bounds;
+          std::stringstream asFortran;
+          Fortran::lower::AddrAndBoundsInfo info =
+              Fortran::lower::gatherDataOperandAddrAndBounds<
+                  Fortran::parser::OmpObject, mlir::omp::DataBoundsOp,
+                  mlir::omp::DataBoundsType>(
+                  converter, firOpBuilder, semaCtx, stmtCtx, ompObject,
+                  clauseLocation, asFortran, bounds, treatIndexAsSection);
+
+          auto origSymbol =
+              converter.getSymbolAddress(*getOmpObjectSymbol(ompObject));
+          mlir::Value symAddr = info.addr;
+          if (origSymbol && fir::isTypeWithDescriptor(origSymbol.getType()))
+            symAddr = origSymbol;
+
+          // Explicit map captures are captured ByRef by default,
+          // optimisation passes may alter this to ByCopy or other capture
+          // types to optimise
+          mlir::Value mapOp = createMapInfoOp(
+              firOpBuilder, clauseLocation, symAddr, mlir::Value{},
+              asFortran.str(), bounds, {},
+              static_cast<
+                  std::underlying_type_t<llvm::omp::OpenMPOffloadMappingFlags>>(
+                  mapTypeBits),
+              mlir::omp::VariableCaptureKind::ByRef, symAddr.getType());
+
+          mapOperands.push_back(mapOp);
+        }
+      });
+}
+
+template <typename... Ts>
+void ClauseProcessor::processTODO(mlir::Location currentLocation,
+                                  llvm::omp::Directive directive) const {
+  auto checkUnhandledClause = [&](const auto *x) {
+    if (!x)
+      return;
+    TODO(currentLocation,
+         "Unhandled clause " +
+             llvm::StringRef(Fortran::parser::ParseTreeDumper::GetNodeName(*x))
+                 .upper() +
+             " in " + llvm::omp::getOpenMPDirectiveName(directive).upper() +
+             " construct");
+  };
+
+  for (ClauseIterator it = clauses.v.begin(); it != clauses.v.end(); ++it)
+    (checkUnhandledClause(std::get_if<Ts>(&it->u)), ...);
+}
+
+template <typename T>
+ClauseProcessor::ClauseIterator
+ClauseProcessor::findClause(ClauseIterator begin, ClauseIterator end) {
+  for (ClauseIterator it = begin; it != end; ++it) {
+    if (std::get_if<T>(&it->u))
+      return it;
+  }
+
+  return end;
+}
+
+template <typename T>
+const T *ClauseProcessor::findUniqueClause(
+    const Fortran::parser::CharBlock **source) const {
+  ClauseIterator it = findClause<T>(clauses.v.begin(), clauses.v.end());
+  if (it != clauses.v.end()) {
+    if (source)
+      *source = &it->source;
+    return &std::get<T>(it->u);
+  }
+  return nullptr;
+}
+
+template <typename T>
+bool ClauseProcessor::findRepeatableClause(
+    std::function<void(const T *, const Fortran::parser::CharBlock &source)>
+        callbackFn) const {
+  bool found = false;
+  ClauseIterator nextIt, endIt = clauses.v.end();
+  for (ClauseIterator it = clauses.v.begin(); it != endIt; it = nextIt) {
+    nextIt = findClause<T>(it, endIt);
+
+    if (nextIt != endIt) {
+      callbackFn(&std::get<T>(nextIt->u), nextIt->source);
+      found = true;
+      ++nextIt;
+    }
+  }
+  return found;
+}
+
+template <typename T>
+bool ClauseProcessor::markClauseOccurrence(mlir::UnitAttr &result) const {
+  if (findUniqueClause<T>()) {
+    result = converter.getFirOpBuilder().getUnitAttr();
+    return true;
+  }
+  return false;
+}
+
+} // namespace omp
+} // namespace lower
+} // namespace Fortran
+
+#endif // FORTRAN_LOWER_CLAUASEPROCESSOR_H