[flang-commits] [flang] [flang][OpenMP] Support tasks' implicit firstprivate DSA (PR #85989)

Leandro Lupori via flang-commits flang-commits at lists.llvm.org
Fri May 3 11:29:09 PDT 2024


https://github.com/luporl updated https://github.com/llvm/llvm-project/pull/85989

>From 1d2a71343a02debf8acee35663384c94f621e025 Mon Sep 17 00:00:00 2001
From: Leandro Lupori <leandro.lupori at linaro.org>
Date: Fri, 3 May 2024 12:15:51 +0000
Subject: [PATCH] [flang][OpenMP] Support tasks' implicit firstprivate DSA

Handle implicit firstprivate DSAs on task generating constructs.

Fixes https://github.com/llvm/llvm-project/issues/64480
---
 flang/include/flang/Semantics/symbol.h        |   3 +-
 .../lib/Lower/OpenMP/DataSharingProcessor.cpp | 117 +++++++-
 flang/lib/Lower/OpenMP/DataSharingProcessor.h |  13 +-
 flang/lib/Semantics/resolve-directives.cpp    | 106 ++++++-
 .../Lower/OpenMP/default-clause-byref.f90     |   4 +-
 flang/test/Lower/OpenMP/default-clause.f90    |   4 +-
 flang/test/Lower/OpenMP/implicit-dsa.f90      | 275 ++++++++++++++++++
 flang/test/Semantics/OpenMP/implicit-dsa.f90  | 158 ++++++++++
 flang/test/Semantics/OpenMP/symbol08.f90      |   2 +-
 9 files changed, 642 insertions(+), 40 deletions(-)
 create mode 100644 flang/test/Lower/OpenMP/implicit-dsa.f90
 create mode 100644 flang/test/Semantics/OpenMP/implicit-dsa.f90

diff --git a/flang/include/flang/Semantics/symbol.h b/flang/include/flang/Semantics/symbol.h
index 4d0a993d02752c..50f7b68d80cb17 100644
--- a/flang/include/flang/Semantics/symbol.h
+++ b/flang/include/flang/Semantics/symbol.h
@@ -745,7 +745,8 @@ class Symbol {
       OmpCommonBlock, OmpReduction, OmpAligned, OmpNontemporal, OmpAllocate,
       OmpDeclarativeAllocateDirective, OmpExecutableAllocateDirective,
       OmpDeclareSimd, OmpDeclareTarget, OmpThreadprivate, OmpDeclareReduction,
-      OmpFlushed, OmpCriticalLock, OmpIfSpecified, OmpNone, OmpPreDetermined);
+      OmpFlushed, OmpCriticalLock, OmpIfSpecified, OmpNone, OmpPreDetermined,
+      OmpImplicit);
   using Flags = common::EnumSet<Flag, Flag_enumSize>;
 
   const Scope &owner() const { return *owner_; }
diff --git a/flang/lib/Lower/OpenMP/DataSharingProcessor.cpp b/flang/lib/Lower/OpenMP/DataSharingProcessor.cpp
index 2a418396cdafc4..ad3b5ed54c7ac4 100644
--- a/flang/lib/Lower/OpenMP/DataSharingProcessor.cpp
+++ b/flang/lib/Lower/OpenMP/DataSharingProcessor.cpp
@@ -27,8 +27,10 @@ void DataSharingProcessor::processStep1(
     llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms) {
   collectSymbolsForPrivatization();
   collectDefaultSymbols();
+  collectImplicitSymbols();
   privatize(clauseOps, privateSyms);
   defaultPrivatize(clauseOps, privateSyms);
+  implicitPrivatize(clauseOps, privateSyms);
   insertBarrier();
 }
 
@@ -302,6 +304,48 @@ void DataSharingProcessor::insertLastPrivateCompare(mlir::Operation *op) {
   }
 }
 
+static const Fortran::parser::CharBlock *
+getSource(const Fortran::semantics::SemanticsContext &semaCtx,
+          const Fortran::lower::pft::Evaluation &eval) {
+  const Fortran::parser::CharBlock *source = nullptr;
+
+  auto ompConsVisit = [&](const Fortran::parser::OpenMPConstruct &x) {
+    std::visit(Fortran::common::visitors{
+                   [&](const Fortran::parser::OpenMPSectionsConstruct &x) {
+                     source = &std::get<0>(x.t).source;
+                   },
+                   [&](const Fortran::parser::OpenMPLoopConstruct &x) {
+                     source = &std::get<0>(x.t).source;
+                   },
+                   [&](const Fortran::parser::OpenMPBlockConstruct &x) {
+                     source = &std::get<0>(x.t).source;
+                   },
+                   [&](const Fortran::parser::OpenMPCriticalConstruct &x) {
+                     source = &std::get<0>(x.t).source;
+                   },
+                   [&](const Fortran::parser::OpenMPAtomicConstruct &x) {
+                     std::visit([&](const auto &x) { source = &x.source; },
+                                x.u);
+                   },
+                   [&](const auto &x) { source = &x.source; },
+               },
+               x.u);
+  };
+
+  eval.visit(Fortran::common::visitors{
+      [&](const Fortran::parser::OpenMPConstruct &x) { ompConsVisit(x); },
+      [&](const Fortran::parser::OpenMPDeclarativeConstruct &x) {
+        source = &x.source;
+      },
+      [&](const Fortran::parser::OmpEndLoopDirective &x) {
+        source = &x.source;
+      },
+      [&](const auto &x) {},
+  });
+
+  return source;
+}
+
 void DataSharingProcessor::collectSymbolsInNestedRegions(
     Fortran::lower::pft::Evaluation &eval,
     Fortran::semantics::Symbol::Flag flag,
@@ -329,11 +373,49 @@ void DataSharingProcessor::collectSymbolsInNestedRegions(
 // Later, in current context, all symbols in the set
 // `defaultSymbols` - `symbolsInNestedRegions` will be privatized.
 void DataSharingProcessor::collectSymbols(
-    Fortran::semantics::Symbol::Flag flag) {
-  converter.collectSymbolSet(eval, defaultSymbols, flag,
+    Fortran::semantics::Symbol::Flag flag,
+    llvm::SetVector<const Fortran::semantics::Symbol *> &symbols) {
+  // Collect all scopes associated with 'eval'.
+  llvm::SetVector<const Fortran::semantics::Scope *> clauseScopes;
+  std::function<void(const Fortran::semantics::Scope *)> collectScopes =
+      [&](const Fortran::semantics::Scope *scope) {
+        clauseScopes.insert(scope);
+        for (const Fortran::semantics::Scope &child : scope->children())
+          collectScopes(&child);
+      };
+  const Fortran::parser::CharBlock *source =
+      clauses.empty() ? getSource(semaCtx, eval) : &clauses.front().source;
+  const Fortran::semantics::Scope *curScope = nullptr;
+  if (source && !source->empty()) {
+    curScope = &semaCtx.FindScope(*source);
+    collectScopes(curScope);
+  }
+  // Collect all symbols referenced in the evaluation being processed,
+  // that matches 'flag'.
+  llvm::SetVector<const Fortran::semantics::Symbol *> allSymbols;
+  converter.collectSymbolSet(eval, allSymbols, flag,
                              /*collectSymbols=*/true,
                              /*collectHostAssociatedSymbols=*/true);
+  llvm::SetVector<const Fortran::semantics::Symbol *> symbolsInNestedRegions;
   collectSymbolsInNestedRegions(eval, flag, symbolsInNestedRegions);
+  // Filter-out symbols that must not be privatized.
+  bool collectImplicit = flag == Fortran::semantics::Symbol::Flag::OmpImplicit;
+  auto isPrivatizable = [](const Fortran::semantics::Symbol &sym) -> bool {
+    return !Fortran::semantics::IsProcedure(sym) &&
+           !sym.GetUltimate().has<Fortran::semantics::DerivedTypeDetails>() &&
+           !sym.GetUltimate().has<Fortran::semantics::NamelistDetails>() &&
+           !Fortran::semantics::IsImpliedDoIndex(sym.GetUltimate());
+  };
+  for (const auto *sym : allSymbols) {
+    assert(curScope && "couldn't find current scope");
+    if (isPrivatizable(*sym) && !symbolsInNestedRegions.contains(sym) &&
+        !privatizedSymbols.contains(sym) &&
+        !sym->test(Fortran::semantics::Symbol::Flag::OmpPreDetermined) &&
+        (collectImplicit ||
+         !sym->test(Fortran::semantics::Symbol::Flag::OmpImplicit)) &&
+        clauseScopes.contains(&sym->owner()))
+      symbols.insert(sym);
+  }
 }
 
 void DataSharingProcessor::collectDefaultSymbols() {
@@ -342,13 +424,22 @@ void DataSharingProcessor::collectDefaultSymbols() {
     if (const auto *defaultClause =
             std::get_if<omp::clause::Default>(&clause.u)) {
       if (defaultClause->v == DataSharingAttribute::Private)
-        collectSymbols(Fortran::semantics::Symbol::Flag::OmpPrivate);
+        collectSymbols(Fortran::semantics::Symbol::Flag::OmpPrivate,
+                       defaultSymbols);
       else if (defaultClause->v == DataSharingAttribute::Firstprivate)
-        collectSymbols(Fortran::semantics::Symbol::Flag::OmpFirstPrivate);
+        collectSymbols(Fortran::semantics::Symbol::Flag::OmpFirstPrivate,
+                       defaultSymbols);
     }
   }
 }
 
+void DataSharingProcessor::collectImplicitSymbols() {
+  // There will be no implicit symbols when a default clause is present.
+  if (defaultSymbols.empty())
+    collectSymbols(Fortran::semantics::Symbol::Flag::OmpImplicit,
+                   implicitSymbols);
+}
+
 void DataSharingProcessor::privatize(
     mlir::omp::PrivateClauseOps *clauseOps,
     llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms) {
@@ -378,15 +469,15 @@ void DataSharingProcessor::copyLastPrivatize(mlir::Operation *op) {
 void DataSharingProcessor::defaultPrivatize(
     mlir::omp::PrivateClauseOps *clauseOps,
     llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms) {
-  for (const Fortran::semantics::Symbol *sym : defaultSymbols) {
-    if (!Fortran::semantics::IsProcedure(*sym) &&
-        !sym->GetUltimate().has<Fortran::semantics::DerivedTypeDetails>() &&
-        !sym->GetUltimate().has<Fortran::semantics::NamelistDetails>() &&
-        !Fortran::semantics::IsImpliedDoIndex(sym->GetUltimate()) &&
-        !symbolsInNestedRegions.contains(sym) &&
-        !privatizedSymbols.contains(sym))
-      doPrivatize(sym, clauseOps, privateSyms);
-  }
+  for (const Fortran::semantics::Symbol *sym : defaultSymbols)
+    doPrivatize(sym, clauseOps, privateSyms);
+}
+
+void DataSharingProcessor::implicitPrivatize(
+    mlir::omp::PrivateClauseOps *clauseOps,
+    llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms) {
+  for (const Fortran::semantics::Symbol *sym : implicitSymbols)
+    doPrivatize(sym, clauseOps, privateSyms);
 }
 
 void DataSharingProcessor::doPrivatize(
diff --git a/flang/lib/Lower/OpenMP/DataSharingProcessor.h b/flang/lib/Lower/OpenMP/DataSharingProcessor.h
index 5d1bce4f5036a4..ec6848f7bba365 100644
--- a/flang/lib/Lower/OpenMP/DataSharingProcessor.h
+++ b/flang/lib/Lower/OpenMP/DataSharingProcessor.h
@@ -39,10 +39,11 @@ class DataSharingProcessor {
   // Symbols in private, firstprivate, and/or lastprivate clauses.
   llvm::SetVector<const Fortran::semantics::Symbol *> privatizedSymbols;
   llvm::SetVector<const Fortran::semantics::Symbol *> defaultSymbols;
-  llvm::SetVector<const Fortran::semantics::Symbol *> symbolsInNestedRegions;
+  llvm::SetVector<const Fortran::semantics::Symbol *> implicitSymbols;
   llvm::DenseMap<const Fortran::semantics::Symbol *, mlir::omp::PrivateClauseOp>
       symToPrivatizer;
   Fortran::lower::AbstractConverter &converter;
+  Fortran::semantics::SemanticsContext &semaCtx;
   fir::FirOpBuilder &firOpBuilder;
   omp::List<omp::Clause> clauses;
   Fortran::lower::pft::Evaluation &eval;
@@ -50,7 +51,9 @@ class DataSharingProcessor {
   Fortran::lower::SymMap *symTable;
 
   bool needBarrier();
-  void collectSymbols(Fortran::semantics::Symbol::Flag flag);
+  void
+  collectSymbols(Fortran::semantics::Symbol::Flag flag,
+                 llvm::SetVector<const Fortran::semantics::Symbol *> &symbols);
   void collectSymbolsInNestedRegions(
       Fortran::lower::pft::Evaluation &eval,
       Fortran::semantics::Symbol::Flag flag,
@@ -62,12 +65,16 @@ class DataSharingProcessor {
   void collectSymbolsForPrivatization();
   void insertBarrier();
   void collectDefaultSymbols();
+  void collectImplicitSymbols();
   void privatize(
       mlir::omp::PrivateClauseOps *clauseOps,
       llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms);
   void defaultPrivatize(
       mlir::omp::PrivateClauseOps *clauseOps,
       llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms);
+  void implicitPrivatize(
+      mlir::omp::PrivateClauseOps *clauseOps,
+      llvm::SmallVectorImpl<const Fortran::semantics::Symbol *> *privateSyms);
   void doPrivatize(
       const Fortran::semantics::Symbol *sym,
       mlir::omp::PrivateClauseOps *clauseOps,
@@ -89,7 +96,7 @@ class DataSharingProcessor {
                        Fortran::lower::pft::Evaluation &eval,
                        bool useDelayedPrivatization = false,
                        Fortran::lower::SymMap *symTable = nullptr)
-      : hasLastPrivateOp(false), converter(converter),
+      : hasLastPrivateOp(false), converter(converter), semaCtx(semaCtx),
         firOpBuilder(converter.getFirOpBuilder()), clauses(clauses), eval(eval),
         useDelayedPrivatization(useDelayedPrivatization), symTable(symTable) {}
 
diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index c99b1c413970ef..9c5d81be7ab7fd 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -2028,34 +2028,108 @@ void OmpAttributeVisitor::Post(const parser::Name &name) {
       if (found->test(semantics::Symbol::Flag::OmpThreadprivate))
         return;
     }
-    std::vector<Symbol *> defaultDSASymbols;
+
+    // Implicitly determined DSAs
+    // OMP 5.2 5.1.1 - Variables Referenced in a Construct
+    Symbol *lastDeclSymbol = nullptr;
+    std::optional<Symbol::Flag> prevDSA;
     for (int dirDepth{0}; dirDepth < (int)dirContext_.size(); ++dirDepth) {
       DirContext &dirContext = dirContext_[dirDepth];
-      bool hasDataSharingAttr{false};
+      std::optional<Symbol::Flag> dsa;
+
       for (auto symMap : dirContext.objectWithDSA) {
         // if the `symbol` already has a data-sharing attribute
         if (symMap.first->name() == name.symbol->name()) {
-          hasDataSharingAttr = true;
+          dsa = symMap.second;
           break;
         }
       }
-      if (hasDataSharingAttr) {
-        if (defaultDSASymbols.size())
-          symbol = &MakeAssocSymbol(symbol->name(), *defaultDSASymbols.back(),
+
+      // When handling each implicit rule, either a new private symbol is
+      // declared or the last declared symbol is used.
+      // In the latter case, it's necessary to insert a new symbol in the scope
+      // being processed, associated with the last declared symbol.
+      // This captures the fact that, although we are using the last declared
+      // symbol, its DSA could be different in this scope.
+      // Also, because of how symbols are collected in lowering, not inserting
+      // a new symbol in this scope could lead to the conclusion that the
+      // symbol was declared in this construct, which would result in wrong
+      // privatization code being generated.
+      // Consider the following example:
+      //
+      // !$omp parallel default(private)              ! p1
+      //   !$omp parallel default(private) shared(x)  ! p2
+      //     x = 10
+      //   !$omp end parallel
+      // !$omp end parallel
+      //
+      // If a new x symbol was not inserted in the inner parallel construct
+      // (p2), it would use the x symbol definition from the enclosing scope.
+      // Then, when p2's default symbols were collected in lowering, the x
+      // symbol from the outer parallel construct (p1) would be collected, as
+      // it would have the private flag set (note that symbols that don't have
+      // any private flag are considered as shared).
+      // This would make x appear to be defined in p2, causing it to be
+      // privatized in p2 and its privatization in p1 to be skipped.
+      auto declNewSymbol = [&](Symbol::Flag flag) {
+        Symbol *hostSymbol =
+            lastDeclSymbol ? lastDeclSymbol : &symbol->GetUltimate();
+        lastDeclSymbol = DeclarePrivateAccessEntity(
+            *hostSymbol, flag, context_.FindScope(dirContext.directiveSource));
+        return lastDeclSymbol;
+      };
+      auto useLastDeclSymbol = [&]() {
+        if (lastDeclSymbol)
+          MakeAssocSymbol(symbol->name(), *lastDeclSymbol,
               context_.FindScope(dirContext.directiveSource));
+      };
+
+      if (dsa.has_value()) {
+        useLastDeclSymbol();
+        prevDSA = dsa;
         continue;
       }
 
-      if (dirContext.defaultDSA == semantics::Symbol::Flag::OmpPrivate ||
-          dirContext.defaultDSA == semantics::Symbol::Flag::OmpFirstPrivate) {
-        Symbol *hostSymbol = defaultDSASymbols.size() ? defaultDSASymbols.back()
-                                                      : &symbol->GetUltimate();
-        defaultDSASymbols.push_back(
-            DeclarePrivateAccessEntity(*hostSymbol, dirContext.defaultDSA,
-                context_.FindScope(dirContext.directiveSource)));
-      } else if (defaultDSASymbols.size())
-        symbol = &MakeAssocSymbol(symbol->name(), *defaultDSASymbols.back(),
-            context_.FindScope(dirContext.directiveSource));
+      bool taskGenDir = llvm::omp::taskGeneratingSet.test(dirContext.directive);
+      bool targetDir = llvm::omp::allTargetSet.test(dirContext.directive);
+      bool parallelDir = llvm::omp::allParallelSet.test(dirContext.directive);
+
+      if (dirContext.defaultDSA == Symbol::Flag::OmpPrivate ||
+          dirContext.defaultDSA == Symbol::Flag::OmpFirstPrivate ||
+          dirContext.defaultDSA == Symbol::Flag::OmpShared) {
+        // 1) default
+        // Allowed only with parallel, teams and task generating constructs.
+        assert(parallelDir || taskGenDir ||
+            llvm::omp::allTeamsSet.test(dirContext.directive));
+        if (dirContext.defaultDSA != Symbol::Flag::OmpShared)
+          declNewSymbol(dirContext.defaultDSA);
+        else
+          useLastDeclSymbol();
+        dsa = dirContext.defaultDSA;
+      } else if (parallelDir) {
+        // 2) parallel -> shared
+        useLastDeclSymbol();
+        dsa = Symbol::Flag::OmpShared;
+      } else if (!taskGenDir && !targetDir) {
+        // 3) enclosing context
+        useLastDeclSymbol();
+        dsa = prevDSA;
+      } else if (targetDir) {
+        // TODO 4) not mapped target variable -> firstprivate
+        dsa = prevDSA;
+      } else if (taskGenDir) {
+        // TODO 5) dummy arg in orphaned taskgen construct -> firstprivate
+        if (prevDSA == Symbol::Flag::OmpShared) {
+          // 6) shared in enclosing context -> shared
+          useLastDeclSymbol();
+          dsa = Symbol::Flag::OmpShared;
+        } else {
+          // 7) firstprivate
+          dsa = Symbol::Flag::OmpFirstPrivate;
+          declNewSymbol(*dsa)->set(Symbol::Flag::OmpImplicit);
+        }
+      }
+      prevDSA = dsa;
     }
   } // within OpenMP construct
 }
diff --git a/flang/test/Lower/OpenMP/default-clause-byref.f90 b/flang/test/Lower/OpenMP/default-clause-byref.f90
index ec8bfbc397d2ef..62ba67e5962f49 100644
--- a/flang/test/Lower/OpenMP/default-clause-byref.f90
+++ b/flang/test/Lower/OpenMP/default-clause-byref.f90
@@ -240,14 +240,12 @@ subroutine nested_default_clause_tests
 !CHECK: omp.terminator
 !CHECK: }
 !CHECK: omp.parallel {
-!CHECK: %[[PRIVATE_INNER_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFnested_default_clause_testsEz"}
-!CHECK: %[[PRIVATE_INNER_Z_DECL:.*]]:2 = hlfir.declare %[[PRIVATE_INNER_Z]] {uniq_name = "_QFnested_default_clause_testsEz"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 !CHECK: %[[PRIVATE_INNER_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFnested_default_clause_testsEw"}
 !CHECK: %[[PRIVATE_INNER_W_DECL:.*]]:2 = hlfir.declare %[[PRIVATE_INNER_W]] {uniq_name = "_QFnested_default_clause_testsEw"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 !CHECK: %[[PRIVATE_INNER_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
 !CHECK: %[[PRIVATE_INNER_X_DECL:.*]]:2 = hlfir.declare %[[PRIVATE_INNER_X]] {uniq_name = "_QFnested_default_clause_testsEx"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 !CHECK: %[[TEMP_1:.*]] = fir.load %[[PRIVATE_INNER_X_DECL]]#0 : !fir.ref<i32>
-!CHECK: %[[TEMP_2:.*]] = fir.load %[[PRIVATE_INNER_Z_DECL]]#0 : !fir.ref<i32>
+!CHECK: %[[TEMP_2:.*]] = fir.load %[[PRIVATE_Z_DECL]]#0 : !fir.ref<i32>
 !CHECK: %[[RESULT:.*]] = arith.addi %{{.*}}, %{{.*}} : i32
 !CHECK: hlfir.assign %[[RESULT]] to %[[PRIVATE_INNER_W_DECL]]#0 : i32, !fir.ref<i32>
 !CHECK: omp.terminator
diff --git a/flang/test/Lower/OpenMP/default-clause.f90 b/flang/test/Lower/OpenMP/default-clause.f90
index c9e76780de5de6..a90f0f4ef5f841 100644
--- a/flang/test/Lower/OpenMP/default-clause.f90
+++ b/flang/test/Lower/OpenMP/default-clause.f90
@@ -250,14 +250,12 @@ subroutine nested_default_clause_test1
 !CHECK: omp.terminator
 !CHECK: }
 !CHECK: omp.parallel {
-!CHECK: %[[PRIVATE_INNER_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFnested_default_clause_test2Ez"}
-!CHECK: %[[PRIVATE_INNER_Z_DECL:.*]]:2 = hlfir.declare %[[PRIVATE_INNER_Z]] {uniq_name = "_QFnested_default_clause_test2Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 !CHECK: %[[PRIVATE_INNER_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFnested_default_clause_test2Ew"}
 !CHECK: %[[PRIVATE_INNER_W_DECL:.*]]:2 = hlfir.declare %[[PRIVATE_INNER_W]] {uniq_name = "_QFnested_default_clause_test2Ew"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 !CHECK: %[[PRIVATE_INNER_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_test2Ex"}
 !CHECK: %[[PRIVATE_INNER_X_DECL:.*]]:2 = hlfir.declare %[[PRIVATE_INNER_X]] {uniq_name = "_QFnested_default_clause_test2Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 !CHECK: %[[TEMP_1:.*]] = fir.load %[[PRIVATE_INNER_X_DECL]]#0 : !fir.ref<i32>
-!CHECK: %[[TEMP_2:.*]] = fir.load %[[PRIVATE_INNER_Z_DECL]]#0 : !fir.ref<i32>
+!CHECK: %[[TEMP_2:.*]] = fir.load %[[PRIVATE_Z_DECL]]#0 : !fir.ref<i32>
 !CHECK: %[[RESULT:.*]] = arith.addi %{{.*}}, %{{.*}} : i32
 !CHECK: hlfir.assign %[[RESULT]] to %[[PRIVATE_INNER_W_DECL]]#0 : i32, !fir.ref<i32>
 !CHECK: omp.terminator
diff --git a/flang/test/Lower/OpenMP/implicit-dsa.f90 b/flang/test/Lower/OpenMP/implicit-dsa.f90
new file mode 100644
index 00000000000000..0f67d5bfd194f9
--- /dev/null
+++ b/flang/test/Lower/OpenMP/implicit-dsa.f90
@@ -0,0 +1,275 @@
+!RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s
+
+! Checks lowering of OpenMP variables with implicitly determined DSAs.
+
+! Basic cases.
+!CHECK-LABEL: func @_QPimplicit_dsa_test1
+!CHECK:       %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test1Ex"}
+!CHECK:       %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test1Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFimplicit_dsa_test1Ey"}
+!CHECK:       %[[Y_DECL:.*]]:2 = hlfir.declare %[[Y]] {uniq_name = "_QFimplicit_dsa_test1Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Z:.*]] = fir.alloca i32 {bindc_name = "z", uniq_name = "_QFimplicit_dsa_test1Ez"}
+!CHECK:       %[[Z_DECL:.*]]:2 = hlfir.declare %[[Z]] {uniq_name = "_QFimplicit_dsa_test1Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       omp.task {
+!CHECK-NEXT:    %[[PRIV_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFimplicit_dsa_test1Ey"}
+!CHECK-NEXT:    %[[PRIV_Y_DECL:.*]]:2 = hlfir.declare %[[PRIV_Y]] {uniq_name = "_QFimplicit_dsa_test1Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:    %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test1Ex"}
+!CHECK-NEXT:    %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test1Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:    %[[TEMP:.*]] = fir.load %[[X_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:    hlfir.assign %[[TEMP]] to %[[PRIV_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NOT:     fir.alloca
+!CHECK:       }
+!CHECK:       omp.task {
+!CHECK-NOT:     fir.alloca
+!CHECK:       }
+subroutine implicit_dsa_test1
+  integer :: x, y, z
+
+  !$omp task private(y) shared(z)
+    x = y + z
+  !$omp end task
+
+  !$omp task default(shared)
+    x = y + z
+  !$omp end task
+end subroutine
+
+! Nested task with implicit firstprivate DSA variable.
+!CHECK-LABEL: func @_QPimplicit_dsa_test2
+!CHECK: %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test2Ex"}
+!CHECK: %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test2Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK: omp.task {
+!CHECK:   omp.task {
+!CHECK:     %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test2Ex"}
+!CHECK:     %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test2Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:     %[[TEMP:.*]] = fir.load %[[X_DECL]]#0 : !fir.ref<i32>
+!CHECK:     hlfir.assign %[[TEMP]] to %[[PRIV_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:   }
+!CHECK: }
+subroutine implicit_dsa_test2
+  integer :: x
+
+  !$omp task
+    !$omp task
+      x = 1
+    !$omp end task
+  !$omp end task
+end subroutine
+
+! Nested tasks with implicit shared DSA variables.
+!CHECK-LABEL: func @_QPimplicit_dsa_test3
+!CHECK: %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test3Ex"}
+!CHECK: %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test3Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK: %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFimplicit_dsa_test3Ey"}
+!CHECK: %[[Y_DECL:.*]]:2 = hlfir.declare %[[Y]] {uniq_name = "_QFimplicit_dsa_test3Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK: %[[Z:.*]] = fir.alloca i32 {bindc_name = "z", uniq_name = "_QFimplicit_dsa_test3Ez"}
+!CHECK: %[[Z_DECL:.*]]:2 = hlfir.declare %[[Z]] {uniq_name = "_QFimplicit_dsa_test3Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK: omp.parallel {
+!CHECK:   omp.task {
+!CHECK:     %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:     hlfir.assign %[[ONE]] to %[[X_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:     %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:     hlfir.assign %[[ONE]] to %[[Y_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:   }
+!CHECK:   omp.task {
+!CHECK:     %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test3Ex"}
+!CHECK:     %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test3Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:     %[[TEMP:.*]] = fir.load %[[X_DECL]]#0 : !fir.ref<i32>
+!CHECK:     hlfir.assign %[[TEMP]] to %[[PRIV_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:     %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:     hlfir.assign %[[ONE]] to %[[PRIV_X_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:     %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:     hlfir.assign %[[ONE]] to %[[Z_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:   }
+!CHECK: }
+subroutine implicit_dsa_test3
+  integer :: x, y, z
+
+  !$omp parallel
+    !$omp task
+      x = 1
+      y = 1
+    !$omp end task
+
+    !$omp task firstprivate(x)
+      x = 1
+      z = 1
+    !$omp end task
+  !$omp end parallel
+end subroutine
+
+! Task with implicit firstprivate DSA variables, enclosed in private context.
+!CHECK-LABEL: func @_QPimplicit_dsa_test4
+!CHECK:       %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test4Ex"}
+!CHECK:       %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test4Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFimplicit_dsa_test4Ey"}
+!CHECK:       %[[Y_DECL:.*]]:2 = hlfir.declare %[[Y]] {uniq_name = "_QFimplicit_dsa_test4Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Z:.*]] = fir.alloca i32 {bindc_name = "z", uniq_name = "_QFimplicit_dsa_test4Ez"}
+!CHECK:       %[[Z_DECL:.*]]:2 = hlfir.declare %[[Z]] {uniq_name = "_QFimplicit_dsa_test4Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       omp.parallel {
+!CHECK:         %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test4Ex"}
+!CHECK:         %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test4Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:         %[[PRIV_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFimplicit_dsa_test4Ez"}
+!CHECK:         %[[PRIV_Z_DECL:.*]]:2 = hlfir.declare %[[PRIV_Z]] {uniq_name = "_QFimplicit_dsa_test4Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:         %[[PRIV_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFimplicit_dsa_test4Ey"}
+!CHECK:         %[[PRIV_Y_DECL:.*]]:2 = hlfir.declare %[[PRIV_Y]] {uniq_name = "_QFimplicit_dsa_test4Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:         omp.task {
+!CHECK-NEXT:      %[[PRIV2_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test4Ex"}
+!CHECK-NEXT:      %[[PRIV2_X_DECL:.*]]:2 = hlfir.declare %[[PRIV2_X]] {uniq_name = "_QFimplicit_dsa_test4Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP:.*]] = fir.load %[[PRIV_X_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP]] to %[[PRIV2_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NEXT:      %[[PRIV2_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFimplicit_dsa_test4Ez"}
+!CHECK-NEXT:      %[[PRIV2_Z_DECL:.*]]:2 = hlfir.declare %[[PRIV2_Z]] {uniq_name = "_QFimplicit_dsa_test4Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP2:.*]] = fir.load %[[PRIV_Z_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP2]] to %[[PRIV2_Z_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:           %[[ZERO:.*]] = arith.constant 0 : i32
+!CHECK-NEXT:      hlfir.assign %[[ZERO]] to %[[PRIV2_X_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:           %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK-NEXT:      hlfir.assign %[[ONE]] to %[[PRIV2_Z_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:         }
+!CHECK:         omp.task {
+!CHECK-NEXT:      %[[PRIV2_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test4Ex"}
+!CHECK-NEXT:      %[[PRIV2_X_DECL:.*]]:2 = hlfir.declare %[[PRIV2_X]] {uniq_name = "_QFimplicit_dsa_test4Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP:.*]] = fir.load %[[PRIV_X_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP]] to %[[PRIV2_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NEXT:      %[[PRIV2_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFimplicit_dsa_test4Ey"}
+!CHECK-NEXT:      %[[PRIV2_Y_DECL:.*]]:2 = hlfir.declare %[[PRIV2_Y]] {uniq_name = "_QFimplicit_dsa_test4Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP2:.*]] = fir.load %[[PRIV_Y_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP2]] to %[[PRIV2_Y_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:           %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK-NEXT:      hlfir.assign %[[ONE]] to %[[PRIV2_X_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:           %[[ZERO:.*]] = arith.constant 0 : i32
+!CHECK-NEXT:      hlfir.assign %[[ZERO]] to %[[PRIV2_Z_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:         }
+!CHECK:       }
+subroutine implicit_dsa_test4
+  integer :: x, y, z
+
+  !$omp parallel default(private)
+    !$omp task
+      x = 0
+      z = 1
+    !$omp end task
+
+    !$omp task
+      x = 1
+      y = 0
+    !$omp end task
+  !$omp end parallel
+end subroutine
+
+! Inner parallel using implicit firstprivate symbol.
+!CHECK-LABEL: func @_QPimplicit_dsa_test5
+!CHECK: %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test5Ex"}
+!CHECK: %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test5Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK: omp.parallel {
+!CHECK:     %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test5Ex"}
+!CHECK:     %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test5Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:   omp.task {
+!CHECK:     %[[PRIV2_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test5Ex"}
+!CHECK:     %[[PRIV2_X_DECL:.*]]:2 = hlfir.declare %[[PRIV2_X]] {uniq_name = "_QFimplicit_dsa_test5Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:      %[[TEMP:.*]] = fir.load %[[PRIV_X_DECL]]#0 : !fir.ref<i32>
+!CHECK:      hlfir.assign %[[TEMP]] to %[[PRIV2_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:     omp.parallel {
+!CHECK:       %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:       hlfir.assign %[[ONE]] to %[[PRIV2_X_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:     }
+!CHECK:   }
+!CHECK: }
+subroutine implicit_dsa_test5
+  integer :: x
+
+  !$omp parallel default(private)
+    !$omp task
+      !$omp parallel
+        x = 1
+      !$omp end parallel
+    !$omp end task
+  !$omp end parallel
+end subroutine
+
+! Constructs nested inside a task with implicit DSA variables.
+!CHECK-LABEL: func @_QPimplicit_dsa_test6
+!CHECK:       %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test6Ex"}
+!CHECK:       %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test6Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFimplicit_dsa_test6Ey"}
+!CHECK:       %[[Y_DECL:.*]]:2 = hlfir.declare %[[Y]] {uniq_name = "_QFimplicit_dsa_test6Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Z:.*]] = fir.alloca i32 {bindc_name = "z", uniq_name = "_QFimplicit_dsa_test6Ez"}
+!CHECK:       %[[Z_DECL:.*]]:2 = hlfir.declare %[[Z]] {uniq_name = "_QFimplicit_dsa_test6Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       omp.task {
+!CHECK-NEXT:    %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test6Ex"}
+!CHECK-NEXT:    %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test6Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:    %[[TEMP:.*]] = fir.load %[[X_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:    hlfir.assign %[[TEMP]] to %[[PRIV_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NEXT:    %[[PRIV_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFimplicit_dsa_test6Ey"}
+!CHECK-NEXT:    %[[PRIV_Y_DECL:.*]]:2 = hlfir.declare %[[PRIV_Y]] {uniq_name = "_QFimplicit_dsa_test6Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:    %[[TEMP2:.*]] = fir.load %[[Y_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:    hlfir.assign %[[TEMP2]] to %[[PRIV_Y_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NEXT:    %[[PRIV_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFimplicit_dsa_test6Ez"}
+!CHECK-NEXT:    %[[PRIV_Z_DECL:.*]]:2 = hlfir.declare %[[PRIV_Z]] {uniq_name = "_QFimplicit_dsa_test6Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:    %[[TEMP3:.*]] = fir.load %[[Z_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:    hlfir.assign %[[TEMP3]] to %[[PRIV_Z_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:         omp.parallel {
+!CHECK:           %[[PRIV2_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test6Ex"}
+!CHECK:           %[[PRIV2_X_DECL:.*]]:2 = hlfir.declare %[[PRIV2_X]] {uniq_name = "_QFimplicit_dsa_test6Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NOT:       hlfir.assign
+!CHECK:           %[[PRIV2_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFimplicit_dsa_test6Ey"}
+!CHECK:           %[[PRIV2_Y_DECL:.*]]:2 = hlfir.declare %[[PRIV2_Y]] {uniq_name = "_QFimplicit_dsa_test6Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NOT:       hlfir.assign
+!CHECK:           hlfir.assign %{{.*}} to %[[PRIV2_X_DECL]]
+!CHECK:         }
+!CHECK:         omp.parallel {
+!CHECK-NEXT:      %[[PRIV3_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test6Ex"}
+!CHECK-NEXT:      %[[PRIV3_X_DECL:.*]]:2 = hlfir.declare %[[PRIV3_X]] {uniq_name = "_QFimplicit_dsa_test6Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP4:.*]] = fir.load %[[PRIV_X_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP4]] to %[[PRIV3_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NEXT:      %[[PRIV3_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFimplicit_dsa_test6Ez"}
+!CHECK-NEXT:      %[[PRIV3_Z_DECL:.*]]:2 = hlfir.declare %[[PRIV3_Z]] {uniq_name = "_QFimplicit_dsa_test6Ez"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP5:.*]] = fir.load %[[PRIV_Z_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP5]] to %[[PRIV3_Z_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:           hlfir.assign %{{.*}} to %[[PRIV_Y_DECL]]#0 : i32, !fir.ref<i32>
+!CHECK:         }
+!CHECK:       }
+subroutine implicit_dsa_test6
+  integer :: x, y, z
+
+  !$omp task
+    !$omp parallel default(private)
+      x = y
+    !$omp end parallel
+
+    !$omp parallel default(firstprivate) shared(y)
+      y = x + z
+    !$omp end parallel
+  !$omp end task
+end subroutine
+
+! Test taskgroup - it uses the same scope as task.
+!CHECK-LABEL: func @_QPimplicit_dsa_test7
+!CHECK:       %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFimplicit_dsa_test7Ex"}
+!CHECK:       %[[X_DECL:.*]]:2 = hlfir.declare %[[X]] {uniq_name = "_QFimplicit_dsa_test7Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFimplicit_dsa_test7Ey"}
+!CHECK:       %[[Y_DECL:.*]]:2 = hlfir.declare %[[Y]] {uniq_name = "_QFimplicit_dsa_test7Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK:       omp.task {
+!CHECK:         omp.taskgroup {
+!CHECK-NEXT:      %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFimplicit_dsa_test7Ex"}
+!CHECK-NEXT:      %[[PRIV_X_DECL:.*]]:2 = hlfir.declare %[[PRIV_X]] {uniq_name = "_QFimplicit_dsa_test7Ex"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP:.*]] = fir.load %[[X_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP]] to %[[PRIV_X_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK-NEXT:      %[[PRIV_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFimplicit_dsa_test7Ey"}
+!CHECK-NEXT:      %[[PRIV_Y_DECL:.*]]:2 = hlfir.declare %[[PRIV_Y]] {uniq_name = "_QFimplicit_dsa_test7Ey"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+!CHECK-NEXT:      %[[TEMP2:.*]] = fir.load %[[Y_DECL]]#0 : !fir.ref<i32>
+!CHECK-NEXT:      hlfir.assign %[[TEMP2]] to %[[PRIV_Y_DECL]]#0 temporary_lhs : i32, !fir.ref<i32>
+!CHECK:         }
+!CHECK:       }
+subroutine implicit_dsa_test7
+  integer :: x, y
+
+  !$omp task
+    !$omp taskgroup
+      x = y
+    !$omp end taskgroup
+  !$omp end task
+end subroutine
+
+! TODO Test taskloop
diff --git a/flang/test/Semantics/OpenMP/implicit-dsa.f90 b/flang/test/Semantics/OpenMP/implicit-dsa.f90
new file mode 100644
index 00000000000000..92d2421d06f971
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/implicit-dsa.f90
@@ -0,0 +1,158 @@
+! RUN: %python %S/../test_symbols.py %s %flang_fc1 -fopenmp
+
+! Test symbols generated in block constructs that have implicitly
+! determined DSAs.
+
+! Basic cases.
+!DEF: /implicit_dsa_test1 (Subroutine) Subprogram
+subroutine implicit_dsa_test1
+  !DEF: /implicit_dsa_test1/i ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test1/x ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test1/y ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test1/z ObjectEntity INTEGER(4)
+  integer i, x, y, z
+
+  !$omp task private(y) shared(z)
+    !DEF: /implicit_dsa_test1/OtherConstruct1/x (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+    !DEF: /implicit_dsa_test1/OtherConstruct1/y (OmpPrivate) HostAssoc INTEGER(4)
+    !REF: /implicit_dsa_test1/z
+    x = y + z
+  !$omp end task
+
+  !$omp task default(shared)
+    !REF: /implicit_dsa_test1/x
+    !REF: /implicit_dsa_test1/y
+    !REF: /implicit_dsa_test1/z
+    x = y + z
+  !$omp end task
+
+  !$omp taskloop
+    !DEF: /implicit_dsa_test1/OtherConstruct3/i (OmpPrivate, OmpPreDetermined) HostAssoc INTEGER(4)
+    do i = 0, 10
+      !DEF: /implicit_dsa_test1/OtherConstruct3/x (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      !DEF: /implicit_dsa_test1/OtherConstruct3/y (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      !REF: /implicit_dsa_test1/OtherConstruct3/i
+      x = y + i
+    end do
+  !$omp end taskloop
+end subroutine
+
+! Nested task with implicit firstprivate DSA variable.
+!DEF: /implicit_dsa_test2 (Subroutine) Subprogram
+subroutine implicit_dsa_test2
+  !DEF: /implicit_dsa_test2/x ObjectEntity INTEGER(4)
+  integer x
+
+  !$omp task
+    !$omp task
+      !DEF: /implicit_dsa_test2/OtherConstruct1/OtherConstruct1/x (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      x = 1
+    !$omp end task
+  !$omp end task
+end subroutine
+
+! Nested tasks with implicit shared DSA variables.
+!DEF: /implicit_dsa_test3 (Subroutine) Subprogram
+subroutine implicit_dsa_test3
+  !DEF: /implicit_dsa_test3/x ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test3/y ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test3/z ObjectEntity INTEGER(4)
+  integer x, y, z
+
+  !$omp parallel
+    !$omp task
+      !REF: /implicit_dsa_test3/x
+      x = 1
+      !REF: /implicit_dsa_test3/y
+      y = 1
+    !$omp end task
+
+    !$omp task firstprivate(x)
+      !DEF: /implicit_dsa_test3/OtherConstruct1/OtherConstruct2/x (OmpFirstPrivate) HostAssoc INTEGER(4)
+      x = 1
+      !REF: /implicit_dsa_test3/z
+      z = 1
+    !$omp end task
+  !$omp end parallel
+end subroutine
+
+! Task with implicit firstprivate DSA variables, enclosed in private context.
+!DEF: /implicit_dsa_test4 (Subroutine) Subprogram
+subroutine implicit_dsa_test4
+  !DEF: /implicit_dsa_test4/x ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test4/y ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test4/z ObjectEntity INTEGER(4)
+  integer x, y, z
+
+  !$omp parallel default(private)
+    !$omp task
+      !DEF: /implicit_dsa_test4/OtherConstruct1/OtherConstruct1/x (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      x = 0
+      !DEF: /implicit_dsa_test4/OtherConstruct1/OtherConstruct1/z (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      z = 1
+    !$omp end task
+
+    !$omp task
+      !DEF: /implicit_dsa_test4/OtherConstruct1/OtherConstruct2/x (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      x = 1
+      !DEF: /implicit_dsa_test4/OtherConstruct1/OtherConstruct2/y (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      y = 0
+    !$omp end task
+  !$omp end parallel
+end subroutine
+
+! Inner parallel using implicit firstprivate symbol.
+!DEF: /implicit_dsa_test5 (Subroutine) Subprogram
+subroutine implicit_dsa_test5
+  !DEF: /implicit_dsa_test5/x ObjectEntity INTEGER(4)
+  integer x
+
+  !$omp parallel default(private)
+    !$omp task
+      !$omp parallel
+        !DEF: /implicit_dsa_test5/OtherConstruct1/OtherConstruct1/OtherConstruct1/x HostAssoc INTEGER(4)
+        x = 1
+      !$omp end parallel
+    !$omp end task
+  !$omp end parallel
+end subroutine
+
+! Constructs nested inside a task with implicit DSA variables.
+!DEF: /implicit_dsa_test6 (Subroutine) Subprogram
+subroutine implicit_dsa_test6
+  !DEF: /implicit_dsa_test6/x ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test6/y ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test6/z ObjectEntity INTEGER(4)
+  integer x, y, z
+
+  !$omp task
+    !$omp parallel default(private)
+      !DEF: /implicit_dsa_test6/OtherConstruct1/OtherConstruct1/x (OmpPrivate) HostAssoc INTEGER(4)
+      !DEF: /implicit_dsa_test6/OtherConstruct1/OtherConstruct1/y (OmpPrivate) HostAssoc INTEGER(4)
+      x = y
+    !$omp end parallel
+
+    !$omp parallel default(firstprivate) shared(y)
+      !DEF: /implicit_dsa_test6/OtherConstruct1/OtherConstruct2/y HostAssoc INTEGER(4)
+      !DEF: /implicit_dsa_test6/OtherConstruct1/OtherConstruct2/x (OmpFirstPrivate) HostAssocINTEGER(4)
+      !DEF: /implicit_dsa_test6/OtherConstruct1/OtherConstruct2/z (OmpFirstPrivate) HostAssocINTEGER(4)
+      y = x + z
+    !$omp end parallel
+  !$omp end task
+end subroutine
+
+! Test taskgroup - it uses the same scope as task.
+!DEF: /implicit_dsa_test7 (Subroutine) Subprogram
+subroutine implicit_dsa_test7
+  !DEF: /implicit_dsa_test7/x ObjectEntity INTEGER(4)
+  !DEF: /implicit_dsa_test7/y ObjectEntity INTEGER(4)
+  integer x, y
+
+  !$omp task
+    !$omp taskgroup
+      !DEF: /implicit_dsa_test7/OtherConstruct1/x (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      !DEF: /implicit_dsa_test7/OtherConstruct1/y (OmpFirstPrivate, OmpImplicit) HostAssoc INTEGER(4)
+      x = y
+    !$omp end taskgroup
+  !$omp end task
+end subroutine
diff --git a/flang/test/Semantics/OpenMP/symbol08.f90 b/flang/test/Semantics/OpenMP/symbol08.f90
index 50f34b736cdb77..3af85af74ee97c 100644
--- a/flang/test/Semantics/OpenMP/symbol08.f90
+++ b/flang/test/Semantics/OpenMP/symbol08.f90
@@ -94,7 +94,7 @@ subroutine test_taskloop
   !DEF: /test_taskloop/OtherConstruct1/j (OmpPrivate) HostAssoc INTEGER(4)
   !REF: /test_taskloop/OtherConstruct1/i
   do j=1,i
-   !REF: /test_taskloop/a
+   !DEF: /test_taskloop/OtherConstruct1/a (OmpFirstPrivate, OmpImplicit) HostAssoc REAL(4)
    !REF: /test_taskloop/OtherConstruct1/j
    !REF: /test_taskloop/OtherConstruct1/i
    a(j,i) = 3.14



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