[flang-commits] [flang] 435feef - [flang][OpenMP] Lowering support for default clause

Nimish Mishra via flang-commits flang-commits at lists.llvm.org
Fri Aug 12 04:19:29 PDT 2022


Author: Nimish Mishra
Date: 2022-08-12T16:46:26+05:30
New Revision: 435feefbdd6c91faf24fa5e69c4e7c3bc127568a

URL: https://github.com/llvm/llvm-project/commit/435feefbdd6c91faf24fa5e69c4e7c3bc127568a
DIFF: https://github.com/llvm/llvm-project/commit/435feefbdd6c91faf24fa5e69c4e7c3bc127568a.diff

LOG: [flang][OpenMP] Lowering support for default clause

This patch adds lowering support for default clause.

1. During symbol resolution in semantics, should the enclosing context
   have a default data sharing clause defined and a `parser::Name` is not
   attached to an explicit data sharing clause, the
   `semantics::Symbol::Flag::OmpPrivate` flag (in case of
   default(private)) and `semantics::Symbol::Flag::OmpFirstprivate` flag
   (in case of default(firstprivate)) is added to the symbol.

2. During lowering, all symbols having either
   `semantics::Symbol::Flag::OmpPrivate` or
   `semantics::Symbol::Flag::OmpFirstprivate` flag are collected and
   privatised appropriately.

Co-authored-by: Peixin Qiao <qiaopeixin at huawei.com>

Reviewed by: peixin

Differential Revision: https://reviews.llvm.org/D123930

Added: 
    flang/test/Lower/OpenMP/Todo/omp-default-clause-inner-loop.f90
    flang/test/Lower/OpenMP/default-clause.f90
    flang/test/Semantics/OpenMP/omp-default-clause.f90

Modified: 
    flang/include/flang/Lower/AbstractConverter.h
    flang/lib/Lower/Bridge.cpp
    flang/lib/Lower/OpenMP.cpp
    flang/lib/Semantics/resolve-directives.cpp
    flang/test/Lower/OpenMP/omp-parallel-lastprivate-clause-scalar.f90

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Lower/AbstractConverter.h b/flang/include/flang/Lower/AbstractConverter.h
index 0329e74979433..5a2a52335f6ce 100644
--- a/flang/include/flang/Lower/AbstractConverter.h
+++ b/flang/include/flang/Lower/AbstractConverter.h
@@ -106,13 +106,15 @@ class AbstractConverter {
   virtual void copyHostAssociateVar(const Fortran::semantics::Symbol &sym,
                                     mlir::Block *lastPrivBlock = nullptr) = 0;
 
-  /// Collect the set of ultimate symbols of symbols with \p flag in \p eval
-  /// region if \p isUltimateSymbol is true. Otherwise, collect the set of
-  /// symbols with \p flag.
+  /// Collect the set of symbols with \p flag in \p eval
+  /// region if \p collectSymbols is true. Likewise, collect the
+  /// set of the host symbols with \p flag of the associated symbols in \p eval
+  /// region if collectHostAssociatedSymbols is true.
   virtual void collectSymbolSet(
       pft::Evaluation &eval,
       llvm::SetVector<const Fortran::semantics::Symbol *> &symbolSet,
-      Fortran::semantics::Symbol::Flag flag, bool isUltimateSymbol = true) = 0;
+      Fortran::semantics::Symbol::Flag flag, bool collectSymbols = true,
+      bool collectHostAssociatedSymbols = false) = 0;
 
   //===--------------------------------------------------------------------===//
   // Expressions

diff  --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
index 5dec92d90864e..f094e0b2f173f 100644
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -556,13 +556,21 @@ class FirConverter : public Fortran::lower::AbstractConverter {
   void collectSymbolSet(
       Fortran::lower::pft::Evaluation &eval,
       llvm::SetVector<const Fortran::semantics::Symbol *> &symbolSet,
-      Fortran::semantics::Symbol::Flag flag,
-      bool isUltimateSymbol) override final {
+      Fortran::semantics::Symbol::Flag flag, bool collectSymbols,
+      bool checkHostAssociatedSymbols) override final {
     auto addToList = [&](const Fortran::semantics::Symbol &sym) {
-      const Fortran::semantics::Symbol &symbol =
-          isUltimateSymbol ? sym.GetUltimate() : sym;
-      if (symbol.test(flag))
-        symbolSet.insert(&symbol);
+      std::function<void(const Fortran::semantics::Symbol &, bool)>
+          insertSymbols = [&](const Fortran::semantics::Symbol &oriSymbol,
+                              bool collectSymbol) {
+            if (collectSymbol && oriSymbol.test(flag))
+              symbolSet.insert(&oriSymbol);
+            if (checkHostAssociatedSymbols)
+              if (const auto *details{
+                      oriSymbol
+                          .detailsIf<Fortran::semantics::HostAssocDetails>()})
+                insertSymbols(details->symbol(), true);
+          };
+      insertSymbols(sym, collectSymbols);
     };
     Fortran::lower::pft::visitAllSymbols(eval, addToList);
   }

diff  --git a/flang/lib/Lower/OpenMP.cpp b/flang/lib/Lower/OpenMP.cpp
index 24f88f07f7450..b79156ed37fb8 100644
--- a/flang/lib/Lower/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP.cpp
@@ -86,23 +86,34 @@ createPrivateVarSyms(Fortran::lower::AbstractConverter &converter,
 
 template <typename Op>
 static bool privatizeVars(Op &op, Fortran::lower::AbstractConverter &converter,
-                          const Fortran::parser::OmpClauseList &opClauseList) {
+                          const Fortran::parser::OmpClauseList &opClauseList,
+                          Fortran::lower::pft::Evaluation &eval) {
   fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
   auto insPt = firOpBuilder.saveInsertionPoint();
   firOpBuilder.setInsertionPointToStart(firOpBuilder.getAllocaBlock());
   bool hasFirstPrivateOp = false;
   bool hasLastPrivateOp = false;
+  // Symbols in private and/or firstprivate clauses.
+  llvm::SetVector<const Fortran::semantics::Symbol *> privatizedSymbols;
+  auto collectOmpObjectListSymbol =
+      [&](const Fortran::parser::OmpObjectList &ompObjectList,
+          llvm::SetVector<const Fortran::semantics::Symbol *> &symbolSet) {
+        for (const Fortran::parser::OmpObject &ompObject : ompObjectList.v) {
+          Fortran::semantics::Symbol *sym = getOmpObjectSymbol(ompObject);
+          symbolSet.insert(sym);
+        }
+      };
   // We need just one ICmpOp for multiple LastPrivate clauses.
   mlir::arith::CmpIOp cmpOp;
 
   for (const Fortran::parser::OmpClause &clause : opClauseList.v) {
     if (const auto &privateClause =
             std::get_if<Fortran::parser::OmpClause::Private>(&clause.u)) {
-      createPrivateVarSyms(converter, privateClause);
+      collectOmpObjectListSymbol(privateClause->v, privatizedSymbols);
     } else if (const auto &firstPrivateClause =
                    std::get_if<Fortran::parser::OmpClause::Firstprivate>(
                        &clause.u)) {
-      createPrivateVarSyms(converter, firstPrivateClause);
+      collectOmpObjectListSymbol(firstPrivateClause->v, privatizedSymbols);
       hasFirstPrivateOp = true;
     } else if (const auto &lastPrivateClause =
                    std::get_if<Fortran::parser::OmpClause::Lastprivate>(
@@ -167,6 +178,65 @@ static bool privatizeVars(Op &op, Fortran::lower::AbstractConverter &converter,
       hasLastPrivateOp = true;
     }
   }
+
+  // Symbols in regions with default(private/firstprivate) clause.
+  // FIXME: Collect the symbols with private/firstprivate flag in the region of
+  // the construct with default(private/firstprivate) clause excluding the
+  // symbols with the same private/firstprivate flag in the inner nested
+  // regions.
+  llvm::SetVector<const Fortran::semantics::Symbol *> defaultSymbols;
+  llvm::SetVector<const Fortran::semantics::Symbol *> symbolsInNestedRegions;
+  llvm::SetVector<const Fortran::semantics::Symbol *> symbolsInParentRegions;
+  auto collectSymbols = [&](Fortran::semantics::Symbol::Flag flag) {
+    converter.collectSymbolSet(eval, defaultSymbols, flag,
+                               /*collectSymbols=*/true,
+                               /*collectHostAssociatedSymbols=*/true);
+    for (auto &e : eval.getNestedEvaluations()) {
+      if (e.hasNestedEvaluations())
+        converter.collectSymbolSet(e, symbolsInNestedRegions, flag,
+                                   /*collectSymbols=*/true,
+                                   /*collectHostAssociatedSymbols=*/false);
+      else
+        converter.collectSymbolSet(e, symbolsInParentRegions, flag,
+                                   /*collectSymbols=*/false,
+                                   /*collectHostAssociatedSymbols=*/true);
+    }
+  };
+
+  for (const Fortran::parser::OmpClause &clause : opClauseList.v) {
+    if (const auto &defaultClause =
+            std::get_if<Fortran::parser::OmpClause::Default>(&clause.u)) {
+      if (defaultClause->v.v ==
+          Fortran::parser::OmpDefaultClause::Type::Private)
+        collectSymbols(Fortran::semantics::Symbol::Flag::OmpPrivate);
+      else if (defaultClause->v.v ==
+               Fortran::parser::OmpDefaultClause::Type::Firstprivate)
+        collectSymbols(Fortran::semantics::Symbol::Flag::OmpFirstPrivate);
+    }
+  }
+
+  auto privatizeSymbol = [&](const Fortran::semantics::Symbol *sym) {
+    // Privatization for symbols which are pre-determined (like loop index
+    // variables) happen separately, for everything else privatize here.
+    if (sym->test(Fortran::semantics::Symbol::Flag::OmpPreDetermined))
+      return;
+    bool success = converter.createHostAssociateVarClone(*sym);
+    (void)success;
+    assert(success && "Privatization failed due to existing binding");
+    if (sym->test(Fortran::semantics::Symbol::Flag::OmpFirstPrivate)) {
+      converter.copyHostAssociateVar(*sym);
+      hasFirstPrivateOp = true;
+    }
+  };
+
+  for (auto sym : privatizedSymbols)
+    privatizeSymbol(sym);
+
+  for (auto sym : defaultSymbols)
+    if (!symbolsInNestedRegions.contains(sym) &&
+        !symbolsInParentRegions.contains(sym) &&
+        !privatizedSymbols.contains(sym))
+      privatizeSymbol(sym);
   if (hasFirstPrivateOp)
     firOpBuilder.create<mlir::omp::BarrierOp>(converter.getCurrentLocation());
   firOpBuilder.restoreInsertionPoint(insPt);
@@ -233,9 +303,9 @@ static void threadPrivatizeVars(Fortran::lower::AbstractConverter &converter,
   };
 
   llvm::SetVector<const Fortran::semantics::Symbol *> threadprivateSyms;
-  converter.collectSymbolSet(eval, threadprivateSyms,
-                             Fortran::semantics::Symbol::Flag::OmpThreadprivate,
-                             /*isUltimateSymbol=*/false);
+  converter.collectSymbolSet(
+      eval, threadprivateSyms,
+      Fortran::semantics::Symbol::Flag::OmpThreadprivate);
   std::set<Fortran::semantics::SourceName> threadprivateSymNames;
 
   // For a COMMON block, the ThreadprivateOp is generated for itself instead of
@@ -459,7 +529,7 @@ createBodyOfOp(Op &op, Fortran::lower::AbstractConverter &converter,
 
   // Handle privatization. Do not privatize if this is the outer operation.
   if (clauses && !outerCombined) {
-    bool lastPrivateOp = privatizeVars(op, converter, *clauses);
+    bool lastPrivateOp = privatizeVars(op, converter, *clauses, eval);
     // LastPrivatization, due to introduction of
     // new control flow, changes the insertion point,
     // thus restore it.

diff  --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 0bb8798c62c7d..21cb42ee37c6a 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -1490,6 +1490,35 @@ void OmpAttributeVisitor::Post(const parser::Name &name) {
         }
       }
     }
+    std::vector<Symbol *> defaultDSASymbols;
+    for (int dirDepth{0}; dirDepth < (int)dirContext_.size(); ++dirDepth) {
+      DirContext &dirContext = dirContext_[dirDepth];
+      bool hasDataSharingAttr{false};
+      for (auto symMap : dirContext.objectWithDSA) {
+        // if the `symbol` already has a data-sharing attribute
+        if (symMap.first->name() == name.symbol->name()) {
+          hasDataSharingAttr = true;
+          break;
+        }
+      }
+      if (hasDataSharingAttr) {
+        if (defaultDSASymbols.size())
+          symbol = &MakeAssocSymbol(symbol->name(), *defaultDSASymbols.back(),
+              context_.FindScope(dirContext.directiveSource));
+        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));
+    }
   } // within OpenMP construct
 }
 

diff  --git a/flang/test/Lower/OpenMP/Todo/omp-default-clause-inner-loop.f90 b/flang/test/Lower/OpenMP/Todo/omp-default-clause-inner-loop.f90
new file mode 100644
index 0000000000000..fd56038231b19
--- /dev/null
+++ b/flang/test/Lower/OpenMP/Todo/omp-default-clause-inner-loop.f90
@@ -0,0 +1,34 @@
+! This test checks the lowering of parallel do
+
+! RUN: %flang_fc1 -emit-fir -fopenmp %s -o - | FileCheck %s
+! RUN: bbc -fopenmp -emit-fir %s -o - | FileCheck %s
+
+! The string "EXPECTED" denotes the expected FIR
+
+! CHECK: omp.parallel   {
+! EXPECTED: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFEy"}
+! EXPECTED: %[[PRIVATE_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFEz"}
+! CHECK: %[[TEMP:.*]] = fir.alloca i32 {adapt.valuebyref, pinned}
+! CHECK: %[[const_1:.*]] = arith.constant 1 : i32
+! CHECK: %[[const_2:.*]] = arith.constant 10 : i32
+! CHECK: %[[const_3:.*]] = arith.constant 1 : i32
+! CHECK: omp.wsloop   for  (%[[ARG:.*]]) : i32 = (%[[const_1]]) to (%[[const_2]]) inclusive step (%[[const_3]]) {
+! CHECK: fir.store %[[ARG]] to %[[TEMP]] : !fir.ref<i32>
+! EXPECTED: %[[temp_1:.*]] = fir.load %[[PRIVATE_Z]] : !fir.ref<i32>
+! CHECK: %[[temp_1:.*]] = fir.load %{{.*}} : !fir.ref<i32>
+! CHECK: %[[temp_2:.*]] = fir.load %[[TEMP]] : !fir.ref<i32>
+! CHECK: %[[result:.*]] = arith.addi %[[temp_1]], %[[temp_2]] : i32
+! EXPECTED: fir.store %[[result]] to %[[PRIVATE_Y]] : !fir.ref<i32>
+! CHECK: fir.store %[[result]] to %{{.*}} : !fir.ref<i32>
+! CHECK: omp.yield
+! CHECK: }
+! CHECK: omp.terminator
+! CHECK: }
+subroutine nested_default_clause()
+	integer x, y, z
+	!$omp parallel do default(private)
+		do x = 1, 10
+			y = z + x
+		enddo
+	!$omp end parallel do
+end subroutine

diff  --git a/flang/test/Lower/OpenMP/default-clause.f90 b/flang/test/Lower/OpenMP/default-clause.f90
new file mode 100644
index 0000000000000..cc1451b6262db
--- /dev/null
+++ b/flang/test/Lower/OpenMP/default-clause.f90
@@ -0,0 +1,290 @@
+! This test checks lowering of OpenMP parallel directive
+! with `DEFAULT` clause present.
+
+! RUN: %flang_fc1 -emit-fir -fopenmp %s -o - | FileCheck %s
+! RUN: bbc -fopenmp -emit-fir %s -o - | FileCheck %s
+
+
+!CHECK: func @_QQmain() {
+!CHECK: %[[W:.*]] = fir.alloca i32 {bindc_name = "w", uniq_name = "_QFEw"}
+!CHECK: %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFEx"}
+!CHECK: %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFEy"}
+!CHECK: %[[Z:.*]] = fir.alloca i32 {bindc_name = "z", uniq_name = "_QFEz"}
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFEx"}
+!CHECK: %[[const:.*]] = fir.load %[[X]] : !fir.ref<i32>
+!CHECK: fir.store %[[const]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFEy"}
+!CHECK: %[[PRIVATE_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFEw"}
+!CHECK: omp.barrier
+!CHECK: %[[const:.*]] = arith.constant 2 : i32
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: %[[result:.*]] = arith.muli %[[const]], %[[temp]] : i32
+!CHECK: fir.store %[[result]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_W]] : !fir.ref<i32>
+!CHECK: %[[const:.*]] = arith.constant 45 : i32
+!CHECK: %[[result:.*]] = arith.addi %[[temp]], %[[const]] : i32
+!CHECK: fir.store %[[result]] to %[[Z]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+
+program default_clause_lowering
+    integer :: x, y, z, w
+
+    !$omp parallel default(private) firstprivate(x) shared(z)
+        x = y * 2
+        z = w + 45
+    !$omp end parallel
+
+!CHECK: omp.parallel {
+!CHECK: %[[temp:.*]] = fir.load %[[Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+
+    !$omp parallel default(shared)
+        x = y
+    !$omp end parallel
+
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFEx"}
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+
+    !$omp parallel default(none) private(x, y)
+        x = y
+    !$omp end parallel
+
+!CHECK: omp.parallel   {
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFEx"}
+!CHECK: %[[temp:.*]] = fir.load %[[X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+
+    !$omp parallel default(firstprivate) firstprivate(y)
+        x = y
+    !$omp end parallel
+
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFEx"}
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: %[[PRIVATE_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFEw"}
+!CHECK: %[[temp:.*]] = fir.load %[[W]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_W]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: %[[const:.*]] = arith.constant 2 : i32
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: %[[result:.*]] = arith.muli %[[const]], %[[temp]] : i32
+!CHECK: fir.store %[[result]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_W]] : !fir.ref<i32>
+!CHECK: %[[const:.*]] = arith.constant 45 : i32
+!CHECK: %[[result:.*]] = arith.addi %[[temp]], %[[const]] : i32
+!CHECK: fir.store %[[result]] to %[[Z]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+
+    !$omp parallel default(firstprivate) private(x) shared(z)
+        x = y * 2
+        z = w + 45
+    !$omp end parallel
+
+!CHECK: omp.parallel   {
+!CHECK: omp.parallel   {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFEx"}
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFEw"}
+!CHECK: %[[temp:.*]] = fir.load %[[W]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_W]] : !fir.ref<i32>
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFEx"}
+!CHECK: %[[temp:.*]] = fir.load %[[X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_W]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.terminator
+!CHECK: }
+    !$omp parallel
+        !$omp parallel default(private)
+            x = y
+        !$omp end parallel
+
+        !$omp parallel default(firstprivate)
+            w = x
+        !$omp end parallel
+    !$omp end parallel
+
+end program default_clause_lowering
+
+subroutine nested_default_clause_tests
+    integer :: x, y, z, w, k, a
+    
+!CHECK: %[[K:.*]] = fir.alloca i32 {bindc_name = "k", uniq_name = "_QFnested_default_clause_testsEk"}
+!CHECK: %[[W:.*]] = fir.alloca i32 {bindc_name = "w", uniq_name = "_QFnested_default_clause_testsEw"}
+!CHECK: %[[X:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[Y:.*]] = fir.alloca i32 {bindc_name = "y", uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[Z:.*]] = fir.alloca i32 {bindc_name = "z", uniq_name = "_QFnested_default_clause_testsEz"}
+!CHECK: omp.parallel   {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[temp:.*]] = fir.load %[[X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[PRIVATE_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFnested_default_clause_testsEz"}
+!CHECK: %[[PRIVATE_K:.*]] = fir.alloca i32 {bindc_name = "k", pinned, uniq_name = "_QFnested_default_clause_testsEk"}
+!CHECK: omp.barrier
+!CHECK: omp.parallel {
+!CHECK: %[[INNER_PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[INNER_PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[const:.*]] = arith.constant 20 : i32
+!CHECK: fir.store %[[const]] to %[[INNER_PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: %[[const:.*]] = arith.constant 10 : i32
+!CHECK: fir.store %[[const]] to %[[INNER_PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.parallel   {
+!CHECK: %[[INNER_PRIVATE_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFnested_default_clause_testsEw"}
+!CHECK: %[[INNER_PRIVATE_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFnested_default_clause_testsEz"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Z]]
+!CHECK: fir.store %[[temp]] to %[[INNER_PRIVATE_Z]] : !fir.ref<i32>
+!CHECK: %[[INNER_PRIVATE_K:.*]] = fir.alloca i32 {bindc_name = "k", pinned, uniq_name = "_QFnested_default_clause_testsEk"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_K]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[INNER_PRIVATE_K]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: %[[const:.*]] = arith.constant 30 : i32
+!CHECK: fir.store %[[const]] to %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: %[[const:.*]] = arith.constant 40 : i32
+!CHECK: fir.store %[[const]] to %[[INNER_PRIVATE_W]] : !fir.ref<i32>
+!CHECK: %[[const:.*]] = arith.constant 50 : i32
+!CHECK: fir.store %[[const]] to %[[INNER_PRIVATE_Z]] : !fir.ref<i32>
+!CHECK: %[[const:.*]] = arith.constant 40 : i32
+!CHECK: fir.store %[[const]] to %[[INNER_PRIVATE_K]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.terminator
+!CHECK: }
+    !$omp parallel  firstprivate(x) private(y) shared(w) default(private)  
+        !$omp parallel default(private)
+           y = 20
+           x = 10 
+        !$omp end parallel 
+
+        !$omp parallel default(firstprivate) shared(y) private(w) 
+            y = 30
+            w = 40 
+            z = 50
+            k = 40
+        !$omp end parallel
+    !$omp end parallel
+    
+    
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[PRIVATE_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFnested_default_clause_testsEz"}
+!CHECK: %[[PRIVATE_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFnested_default_clause_testsEw"} 
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_INNER_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_INNER_X]] : !fir.ref<i32>
+!CHECK: %[[INNER_PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[INNER_PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: %[[temp:.*]] = fir.load %[[INNER_PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_INNER_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_INNER_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFnested_default_clause_testsEw"} 
+!CHECK: %[[PRIVATE_INNER_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[temp_1:.*]] = fir.load %[[PRIVATE_INNER_X]] : !fir.ref<i32>
+!CHECK: %[[temp_2:.*]] = fir.load %[[PRIVATE_Z]] : !fir.ref<i32>
+!CHECK: %[[result:.*]] = arith.addi %{{.*}}, %{{.*}} : i32
+!CHECK: fir.store %[[result]] to %[[PRIVATE_INNER_W]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+    !$omp parallel default(private)
+        !$omp parallel default(firstprivate)
+            x = y
+        !$omp end parallel
+
+        !$omp parallel default(private) shared(z)
+            w = x + z
+        !$omp end parallel
+    !$omp end parallel    
+    
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[PRIVATE_W:.*]] = fir.alloca i32 {bindc_name = "w", pinned, uniq_name = "_QFnested_default_clause_testsEw"}
+!CHECK: %[[PRIVATE_Z:.*]] = fir.alloca i32 {bindc_name = "z", pinned, uniq_name = "_QFnested_default_clause_testsEz"}
+!CHECK: omp.parallel {
+!CHECK: %[[INNER_PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[INNER_PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[INNER_PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[INNER_PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: %[[temp:.*]] = fir.load %[[INNER_PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[INNER_PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.parallel {
+!CHECK: %[[temp_1:.*]] = fir.load %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[temp_2:.*]] = fir.load %[[PRIVATE_Z]] : !fir.ref<i32>
+!CHECK: %[[temp_3:.*]] = arith.addi %[[temp_1]], %[[temp_2]] : i32
+!CHECK: fir.store %[[temp_3]] to %[[PRIVATE_W]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: }
+    !$omp parallel default(private)
+		!$omp parallel default(firstprivate)
+			x = y
+		!$omp end parallel
+
+		!$omp parallel default(shared)
+			w = x + z
+		!$omp end parallel
+	!$omp end parallel
+
+!CHECK: omp.parallel {
+!CHECK: %[[PRIVATE_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFnested_default_clause_testsEx"}
+!CHECK: %[[temp:.*]] = fir.load %[[X]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: %[[PRIVATE_Y:.*]] = fir.alloca i32 {bindc_name = "y", pinned, uniq_name = "_QFnested_default_clause_testsEy"}
+!CHECK: %[[temp:.*]] = fir.load %[[Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: omp.barrier
+!CHECK: omp.single {
+!CHECK: %[[temp:.*]] = fir.load %[[PRIVATE_Y]] : !fir.ref<i32>
+!CHECK: fir.store %[[temp]] to %[[PRIVATE_X]] : !fir.ref<i32>
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: omp.terminator
+!CHECK: }
+!CHECK: } 
+	!$omp parallel default(firstprivate)
+		!$omp single
+			x = y
+		!$omp end single
+	!$omp end parallel
+end subroutine

diff  --git a/flang/test/Lower/OpenMP/omp-parallel-lastprivate-clause-scalar.f90 b/flang/test/Lower/OpenMP/omp-parallel-lastprivate-clause-scalar.f90
index 7e0aacc353caf..bf42bf57dc033 100644
--- a/flang/test/Lower/OpenMP/omp-parallel-lastprivate-clause-scalar.f90
+++ b/flang/test/Lower/OpenMP/omp-parallel-lastprivate-clause-scalar.f90
@@ -150,12 +150,12 @@ subroutine mult_lastprivate_int2(arg1, arg2)
 
 !CHECK: func.func @_QPfirstpriv_lastpriv_int(%[[ARG1:.*]]: !fir.ref<i32> {fir.bindc_name = "arg1"}, %[[ARG2:.*]]: !fir.ref<i32> {fir.bindc_name = "arg2"}) {
 !CHECK-DAG: omp.parallel  {
+! Lastprivate Allocation
+!CHECK-NEXT: %[[CLONE2:.*]] = fir.alloca i32 {bindc_name = "arg2"
 !CHECK-DAG: %[[CLONE1:.*]] = fir.alloca i32 {bindc_name = "arg1"
 ! Firstprivate update
 !CHECK-NEXT: %[[FPV_LD:.*]] = fir.load %[[ARG1]] : !fir.ref<i32>
 !CHECK-NEXT: fir.store %[[FPV_LD]] to %[[CLONE1]] : !fir.ref<i32>
-! Lastprivate Allocation
-!CHECK-NEXT: %[[CLONE2:.*]] = fir.alloca i32 {bindc_name = "arg2"
 !CHECK-NEXT: omp.barrier
 !CHECK: omp.wsloop for (%[[INDX_WS:.*]]) : {{.*}} {
 

diff  --git a/flang/test/Semantics/OpenMP/omp-default-clause.f90 b/flang/test/Semantics/OpenMP/omp-default-clause.f90
new file mode 100644
index 0000000000000..9cde77be2babe
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/omp-default-clause.f90
@@ -0,0 +1,45 @@
+! RUN: %flang_fc1 -fopenmp -fdebug-dump-symbols %s | FileCheck %s
+
+! Test symbols generated in block constructs in the 
+! presence of `default(...)` clause
+
+program sample
+    !CHECK: a size=4 offset=20: ObjectEntity type: INTEGER(4)
+    !CHECK: k size=4 offset=16: ObjectEntity type: INTEGER(4)
+    !CHECK: w size=4 offset=12: ObjectEntity type: INTEGER(4)
+    !CHECK: x size=4 offset=0: ObjectEntity type: INTEGER(4)
+    !CHECK: y size=4 offset=4: ObjectEntity type: INTEGER(4)
+    !CHECK: z size=4 offset=8: ObjectEntity type: INTEGER(4)
+    integer x, y, z, w, k, a 
+    !$omp parallel  firstprivate(x) private(y) shared(w) default(private)
+        !CHECK: OtherConstruct scope: size=0 alignment=1
+        !CHECK: a (OmpPrivate): HostAssoc
+        !CHECK: k (OmpPrivate): HostAssoc
+        !CHECK: x (OmpFirstPrivate): HostAssoc
+        !CHECK: y (OmpPrivate): HostAssoc
+        !CHECK: z (OmpPrivate): HostAssoc
+        !$omp parallel default(private)
+            !CHECK: OtherConstruct scope: size=0 alignment=1
+            !CHECK: a (OmpPrivate): HostAssoc
+            !CHECK: x (OmpPrivate): HostAssoc
+            !CHECK: y (OmpPrivate): HostAssoc
+            y = 20
+            x = 10
+           !$omp parallel
+                !CHECK: OtherConstruct scope: size=0 alignment=1
+                a = 10
+           !$omp end parallel
+        !$omp end parallel 
+
+        !$omp parallel default(firstprivate) shared(y) private(w)
+            !CHECK: OtherConstruct scope: size=0 alignment=1
+            !CHECK: k (OmpFirstPrivate): HostAssoc
+            !CHECK: w (OmpPrivate): HostAssoc
+            !CHECK: z (OmpFirstPrivate): HostAssoc
+            y = 30
+            w = 40 
+            z = 50 
+            k = 40
+        !$omp end parallel
+    !$omp end parallel  
+end program sample


        


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