[flang][OpenMP] Overhaul implementation of ATOMIC construct

flang/docs/OpenMPSupport.md

@@ -60,3 +60,16 @@ Note : No distinction is made between the support in Parser/Semantics, MLIR, Low
 | target teams distribute parallel loop construct            | P      | device, reduction and dist_schedule clauses are not supported |
 | teams distribute parallel loop simd construct              | P      | reduction, dist_schedule, and linear clauses are not supported |
 | target teams distribute parallel loop simd construct       | P      | device, reduction, dist_schedule and linear clauses are not supported |
+
+## Extensions
+### ATOMIC construct
+The implementation of the ATOMIC construct follows OpenMP 6.0 with the following extensions:
+- `x = x` is an allowed form of ATOMIC UPDATE.
+This is motivated by the fact that the equivalent forms `x = x+0` or `x = x*1` are allowed.
+- Explicit type conversions are allowed in ATOMIC READ, WRITE or UPDATE constructs, and in the capture statement in ATOMIC UPDATE CAPTURE.
+The OpenMP spec requires intrinsic- or pointer-assignments, which include (as per the Fortran standard) implicit type conversions.  Since such conversions need to be handled, allowing explicit conversions comes at no extra cost.
+- A literal `.true.` or `.false.` is an allowed condition in ATOMIC UPDATE COMPARE. [1]
+- A logical variable is an allowed form of the condition even if its value is not computed within the ATOMIC UPDATE COMPARE construct [1].
+- `expr equalop x` is an allowed condition in ATOMIC UPDATE COMPARE. [1]
+
+[1] Code generation for ATOMIC UPDATE COMPARE is not implemented yet.

flang/examples/FeatureList/FeatureList.cpp

@@ -445,13 +445,6 @@ struct NodeVisitor {
   READ_FEATURE(ObjectDecl)
   READ_FEATURE(OldParameterStmt)
   READ_FEATURE(OmpAlignedClause)
-  READ_FEATURE(OmpAtomic)
-  READ_FEATURE(OmpAtomicCapture)
-  READ_FEATURE(OmpAtomicCapture::Stmt1)
-  READ_FEATURE(OmpAtomicCapture::Stmt2)
-  READ_FEATURE(OmpAtomicRead)
-  READ_FEATURE(OmpAtomicUpdate)
-  READ_FEATURE(OmpAtomicWrite)
   READ_FEATURE(OmpBeginBlockDirective)
   READ_FEATURE(OmpBeginLoopDirective)
   READ_FEATURE(OmpBeginSectionsDirective)
@@ -480,7 +473,6 @@ struct NodeVisitor {
   READ_FEATURE(OmpIterationOffset)
   READ_FEATURE(OmpIterationVector)
   READ_FEATURE(OmpEndAllocators)
-  READ_FEATURE(OmpEndAtomic)
   READ_FEATURE(OmpEndBlockDirective)
   READ_FEATURE(OmpEndCriticalDirective)
   READ_FEATURE(OmpEndLoopDirective)
@@ -566,8 +558,6 @@ struct NodeVisitor {
   READ_FEATURE(OpenMPDeclareTargetConstruct)
   READ_FEATURE(OmpMemoryOrderType)
   READ_FEATURE(OmpMemoryOrderClause)
-  READ_FEATURE(OmpAtomicClause)
-  READ_FEATURE(OmpAtomicClauseList)
   READ_FEATURE(OmpAtomicDefaultMemOrderClause)
   READ_FEATURE(OpenMPFlushConstruct)
   READ_FEATURE(OpenMPLoopConstruct)

flang/examples/FlangOmpReport/FlangOmpReportVisitor.cpp

@@ -74,25 +74,19 @@ SourcePosition OpenMPCounterVisitor::getLocation(const OpenMPConstruct &c) {
           // the directive field.
           [&](const auto &c) -> SourcePosition {
             const CharBlock &source{std::get<0>(c.t).source};
-            return (parsing->allCooked().GetSourcePositionRange(source))->first;
+            return parsing->allCooked().GetSourcePositionRange(source)->first;
           },
           [&](const OpenMPAtomicConstruct &c) -> SourcePosition {
-            return std::visit(
-                [&](const auto &o) -> SourcePosition {
-                  const CharBlock &source{std::get<Verbatim>(o.t).source};
-                  return parsing->allCooked()
-                      .GetSourcePositionRange(source)
-                      ->first;
-                },
-                c.u);
+            const CharBlock &source{c.source};
+            return parsing->allCooked().GetSourcePositionRange(source)->first;
           },
           [&](const OpenMPSectionConstruct &c) -> SourcePosition {
             const CharBlock &source{c.source};
-            return (parsing->allCooked().GetSourcePositionRange(source))->first;
+            return parsing->allCooked().GetSourcePositionRange(source)->first;
           },
           [&](const OpenMPUtilityConstruct &c) -> SourcePosition {
             const CharBlock &source{c.source};
-            return (parsing->allCooked().GetSourcePositionRange(source))->first;
+            return parsing->allCooked().GetSourcePositionRange(source)->first;
           },
       },
       c.u);
@@ -157,14 +151,9 @@ std::string OpenMPCounterVisitor::getName(const OpenMPConstruct &c) {
             return normalize_construct_name(source.ToString());
           },
           [&](const OpenMPAtomicConstruct &c) -> std::string {
-            return std::visit(
-                [&](const auto &c) {
-                  // Get source from the verbatim fields
-                  const CharBlock &source{std::get<Verbatim>(c.t).source};
-                  return "atomic-" +
-                      normalize_construct_name(source.ToString());
-                },
-                c.u);
+            auto &dirSpec = std::get<OmpDirectiveSpecification>(c.t);
+            auto &dirName = std::get<OmpDirectiveName>(dirSpec.t);
+            return normalize_construct_name(dirName.source.ToString());
           },
           [&](const OpenMPUtilityConstruct &c) -> std::string {
             const CharBlock &source{c.source};

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

@@ -532,15 +532,6 @@ class ParseTreeDumper {
   NODE(parser, OmpAtClause)
   NODE_ENUM(OmpAtClause, ActionTime)
   NODE_ENUM(OmpSeverityClause, Severity)
-  NODE(parser, OmpAtomic)
-  NODE(parser, OmpAtomicCapture)
-  NODE(OmpAtomicCapture, Stmt1)
-  NODE(OmpAtomicCapture, Stmt2)
-  NODE(parser, OmpAtomicCompare)
-  NODE(parser, OmpAtomicCompareIfStmt)
-  NODE(parser, OmpAtomicRead)
-  NODE(parser, OmpAtomicUpdate)
-  NODE(parser, OmpAtomicWrite)
   NODE(parser, OmpBeginBlockDirective)
   NODE(parser, OmpBeginLoopDirective)
   NODE(parser, OmpBeginSectionsDirective)
@@ -587,7 +578,6 @@ class ParseTreeDumper {
   NODE(parser, OmpDoacrossClause)
   NODE(parser, OmpDestroyClause)
   NODE(parser, OmpEndAllocators)
-  NODE(parser, OmpEndAtomic)
   NODE(parser, OmpEndBlockDirective)
   NODE(parser, OmpEndCriticalDirective)
   NODE(parser, OmpEndLoopDirective)
@@ -716,8 +706,6 @@ class ParseTreeDumper {
   NODE(parser, OpenMPDeclareMapperConstruct)
   NODE_ENUM(common, OmpMemoryOrderType)
   NODE(parser, OmpMemoryOrderClause)
-  NODE(parser, OmpAtomicClause)
-  NODE(parser, OmpAtomicClauseList)
   NODE(parser, OmpAtomicDefaultMemOrderClause)
   NODE(parser, OpenMPDepobjConstruct)
   NODE(parser, OpenMPUtilityConstruct)

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

@@ -4857,94 +4857,37 @@ struct OmpMemoryOrderClause {
   CharBlock source;
 };
 
-// 2.17.7 Atomic construct
-//        atomic-clause -> memory-order-clause | HINT(hint-expression) |
-//        FAIL(memory-order)
-struct OmpAtomicClause {
-  UNION_CLASS_BOILERPLATE(OmpAtomicClause);
-  CharBlock source;
-  std::variant<OmpMemoryOrderClause, OmpFailClause, OmpHintClause> u;
-};
-
-// atomic-clause-list -> [atomic-clause, [atomic-clause], ...]
-struct OmpAtomicClauseList {
-  WRAPPER_CLASS_BOILERPLATE(OmpAtomicClauseList, std::list<OmpAtomicClause>);
-  CharBlock source;
-};
-
-// END ATOMIC
-EMPTY_CLASS(OmpEndAtomic);
-
-// ATOMIC READ
-struct OmpAtomicRead {
-  TUPLE_CLASS_BOILERPLATE(OmpAtomicRead);
-  CharBlock source;
-  std::tuple<OmpAtomicClauseList, Verbatim, OmpAtomicClauseList,
-      Statement<AssignmentStmt>, std::optional<OmpEndAtomic>>
-      t;
-};
-
-// ATOMIC WRITE
-struct OmpAtomicWrite {
-  TUPLE_CLASS_BOILERPLATE(OmpAtomicWrite);
-  CharBlock source;
-  std::tuple<OmpAtomicClauseList, Verbatim, OmpAtomicClauseList,
-      Statement<AssignmentStmt>, std::optional<OmpEndAtomic>>
-      t;
-};
-
-// ATOMIC UPDATE
-struct OmpAtomicUpdate {
-  TUPLE_CLASS_BOILERPLATE(OmpAtomicUpdate);
-  CharBlock source;
-  std::tuple<OmpAtomicClauseList, Verbatim, OmpAtomicClauseList,
-      Statement<AssignmentStmt>, std::optional<OmpEndAtomic>>
-      t;
-};
-
-// ATOMIC CAPTURE
-struct OmpAtomicCapture {
-  TUPLE_CLASS_BOILERPLATE(OmpAtomicCapture);
-  CharBlock source;
-  WRAPPER_CLASS(Stmt1, Statement<AssignmentStmt>);
-  WRAPPER_CLASS(Stmt2, Statement<AssignmentStmt>);
-  std::tuple<OmpAtomicClauseList, Verbatim, OmpAtomicClauseList, Stmt1, Stmt2,
-      OmpEndAtomic>
-      t;
-};
-
-struct OmpAtomicCompareIfStmt {
-  UNION_CLASS_BOILERPLATE(OmpAtomicCompareIfStmt);
-  std::variant<common::Indirection<IfStmt>, common::Indirection<IfConstruct>> u;
-};
-
-// ATOMIC COMPARE (OpenMP 5.1, OPenMP 5.2 spec: 15.8.4)
-struct OmpAtomicCompare {
-  TUPLE_CLASS_BOILERPLATE(OmpAtomicCompare);
+struct OpenMPAtomicConstruct {
+  llvm::omp::Clause GetKind() const;
+  bool IsCapture() const;
+  bool IsCompare() const;
+  TUPLE_CLASS_BOILERPLATE(OpenMPAtomicConstruct);
   CharBlock source;
-  std::tuple<OmpAtomicClauseList, Verbatim, OmpAtomicClauseList,
-      OmpAtomicCompareIfStmt, std::optional<OmpEndAtomic>>
+  std::tuple<OmpDirectiveSpecification, Block,
+      std::optional<OmpDirectiveSpecification>>
       t;
-};
 
-// ATOMIC
-struct OmpAtomic {
-  TUPLE_CLASS_BOILERPLATE(OmpAtomic);
-  CharBlock source;
-  std::tuple<Verbatim, OmpAtomicClauseList, Statement<AssignmentStmt>,
-      std::optional<OmpEndAtomic>>
-      t;
-};
+  // Information filled out during semantic checks to avoid duplication
+  // of analyses.
+  struct Analysis {
+    static constexpr int None = 0;
+    static constexpr int Read = 1;
+    static constexpr int Write = 2;
+    static constexpr int Update = Read | Write;
+    static constexpr int Action = 3; // Bitmask for None, Read, Write, Update
+    static constexpr int IfTrue = 4;
+    static constexpr int IfFalse = 8;
+    static constexpr int Condition = 12; // Bitmask for IfTrue, IfFalse
+
+    struct Op {
+      int what;
+      AssignmentStmt::TypedAssignment assign;
+    };
+    TypedExpr atom, cond;
+    Op op0, op1;
+  };
 
-// 2.17.7 atomic ->
-//        ATOMIC [atomic-clause-list] atomic-construct [atomic-clause-list] |
-//        ATOMIC [atomic-clause-list]
-//        atomic-construct -> READ | WRITE | UPDATE | CAPTURE | COMPARE
-struct OpenMPAtomicConstruct {
-  UNION_CLASS_BOILERPLATE(OpenMPAtomicConstruct);
-  std::variant<OmpAtomicRead, OmpAtomicWrite, OmpAtomicCapture, OmpAtomicUpdate,
-      OmpAtomicCompare, OmpAtomic>
-      u;
+  mutable Analysis analysis;
 };
 
 // OpenMP directives that associate with loop(s)