Index: flang/lib/Lower/OpenMP.cpp
===================================================================
--- flang/lib/Lower/OpenMP.cpp
+++ flang/lib/Lower/OpenMP.cpp
@@ -83,7 +83,8 @@
   fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
   auto insPt = firOpBuilder.saveInsertionPoint();
   firOpBuilder.setInsertionPointToStart(firOpBuilder.getAllocaBlock());
-  bool hasFirstPrivateOp = false;
+  bool hasFirstprivateOp = false;
+  bool hasLastprivateOp = false;
   for (const Fortran::parser::OmpClause &clause : opClauseList.v) {
     if (const auto &privateClause =
             std::get_if<Fortran::parser::OmpClause::Private>(&clause.u)) {
@@ -92,10 +93,20 @@
                    std::get_if<Fortran::parser::OmpClause::Firstprivate>(
                        &clause.u)) {
       createPrivateVarSyms(converter, firstPrivateClause);
-      hasFirstPrivateOp = true;
+      hasFirstprivateOp = true;
+    } else if (std::get_if<Fortran::parser::OmpClause::Lastprivate>(
+                   &clause.u)) {
+      hasLastprivateOp = true;
     }
   }
-  if (hasFirstPrivateOp)
+  // Emit implicit barrier to synchronize threads and avoid data races on
+  // initialization of firstprivate variables and post-update of lastprivate
+  // variables.
+  // FIXME: Emit barrier for lastprivate clause when 'sections' directive has
+  // 'nowait' clause. Otherwise, emit barrier when 'sections' directive has
+  // both firstprivate and lastprivate clause.
+  // TODO: Emit implicit barrier for linear clause. Maybe on somewhere else.
+  if (hasFirstprivateOp && hasLastprivateOp)
     firOpBuilder.create<mlir::omp::BarrierOp>(converter.getCurrentLocation());
   firOpBuilder.restoreInsertionPoint(insPt);
 }
Index: flang/test/Lower/OpenMP/omp-parallel-firstprivate-clause-scalar.f90
===================================================================
--- flang/test/Lower/OpenMP/omp-parallel-firstprivate-clause-scalar.f90
+++ flang/test/Lower/OpenMP/omp-parallel-firstprivate-clause-scalar.f90
@@ -11,7 +11,7 @@
 !FIRDialect:     %[[ARG2_PVT:.*]] = fir.alloca !fir.complex<8> {bindc_name = "arg2", pinned, uniq_name = "_QFfirstprivate_complexEarg2"}
 !FIRDialect:     %[[ARG2_VAL:.*]] = fir.load %[[ARG2]] : !fir.ref<!fir.complex<8>>
 !FIRDialect:     fir.store %[[ARG2_VAL]] to %[[ARG2_PVT]] : !fir.ref<!fir.complex<8>>
-!FIRDialect:     omp.barrier
+!FIRDialect-NOT: omp.barrier
 !FIRDialect:     fir.call @_QPfoo(%[[ARG1_PVT]], %[[ARG2_PVT]]) : (!fir.ref<!fir.complex<4>>, !fir.ref<!fir.complex<8>>) -> ()
 !FIRDialect:     omp.terminator
 !FIRDialect:   }
@@ -46,7 +46,7 @@
 !FIRDialect:    %[[ARG6_PVT:.*]] = fir.alloca i128 {bindc_name = "arg6", pinned, uniq_name = "_QFfirstprivate_integerEarg6"}
 !FIRDialect:    %[[ARG6_VAL:.*]] = fir.load %[[ARG6]] : !fir.ref<i128>
 !FIRDialect:    fir.store %[[ARG6_VAL]] to %[[ARG6_PVT]] : !fir.ref<i128>
-!FIRDialect:    omp.barrier
+!FIRDialect-NOT:omp.barrier
 !FIRDialect:    fir.call @_QPbar(%[[ARG1_PVT]], %[[ARG2_PVT]], %[[ARG3_PVT]], %[[ARG4_PVT]], %[[ARG5_PVT]], %[[ARG6_PVT]]) : (!fir.ref<i32>, !fir.ref<i8>, !fir.ref<i16>, !fir.ref<i32>, !fir.ref<i64>, !fir.ref<i128>) -> ()
 !FIRDialect:    omp.terminator
 !FIRDialect:  }
@@ -82,7 +82,7 @@
 !FIRDialect:     %[[ARG5_PVT:.*]] = fir.alloca !fir.logical<8> {bindc_name = "arg5", pinned, uniq_name = "_QFfirstprivate_logicalEarg5"}
 !FIRDialect:     %[[ARG5_VAL:.*]] = fir.load %[[ARG5]] : !fir.ref<!fir.logical<8>>
 !FIRDialect:     fir.store %[[ARG5_VAL]] to %[[ARG5_PVT]] : !fir.ref<!fir.logical<8>>
-!FIRDialect:     omp.barrier
+!FIRDialect-NOT: omp.barrier
 !FIRDialect:     fir.call @_QPbaz(%[[ARG1_PVT]], %[[ARG2_PVT]], %[[ARG3_PVT]], %[[ARG4_PVT]], %[[ARG5_PVT]]) : (!fir.ref<!fir.logical<4>>, !fir.ref<!fir.logical<1>>, !fir.ref<!fir.logical<2>>, !fir.ref<!fir.logical<4>>, !fir.ref<!fir.logical<8>>) -> ()
 !FIRDialect:     omp.terminator
 !FIRDialect:   }
@@ -120,7 +120,7 @@
 !FIRDialect:     %[[ARG6_PVT:.*]] = fir.alloca f128 {bindc_name = "arg6", pinned, uniq_name = "_QFfirstprivate_realEarg6"}
 !FIRDialect:     %[[ARG6_VAL:.*]] = fir.load %[[ARG6]] : !fir.ref<f128>
 !FIRDialect:     fir.store %[[ARG6_VAL]] to %[[ARG6_PVT]] : !fir.ref<f128>
-!FIRDialect:     omp.barrier
+!FIRDialect-NOT: omp.barrier
 !FIRDialect:     fir.call @_QPqux(%[[ARG1_PVT]], %[[ARG2_PVT]], %[[ARG3_PVT]], %[[ARG4_PVT]], %[[ARG5_PVT]], %[[ARG6_PVT]]) : (!fir.ref<f32>, !fir.ref<f16>, !fir.ref<f32>, !fir.ref<f64>, !fir.ref<f80>, !fir.ref<f128>) -> ()
 !FIRDialect:     omp.terminator
 !FIRDialect:   }
@@ -149,7 +149,6 @@
 !FIRDialect:             %[[B_PRIV_ADDR:.*]] = fir.alloca i32 {bindc_name = "b", pinned, uniq_name = "_QFmultiple_firstprivateEb"}
 !FIRDialect:             %[[B:.*]] = fir.load %[[B_ADDR]] : !fir.ref<i32>
 !FIRDialect:             fir.store %[[B]] to %[[B_PRIV_ADDR]] : !fir.ref<i32>
-!FIRDialect:             omp.barrier
 !FIRDialect-NOT:         omp.barrier
 !FIRDialect:             fir.call @_QPquux(%[[A_PRIV_ADDR]], %[[B_PRIV_ADDR]]) : (!fir.ref<i32>, !fir.ref<i32>) -> ()
 !FIRDialect:             omp.terminator
Index: flang/test/Lower/OpenMP/omp-parallel-wsloop.f90
===================================================================
--- flang/test/Lower/OpenMP/omp-parallel-wsloop.f90
+++ flang/test/Lower/OpenMP/omp-parallel-wsloop.f90
@@ -87,7 +87,7 @@
   ! CHECK:    %[[PRIVATE_NT_REF:.*]] = fir.alloca i32 {bindc_name = "nt", pinned, uniq_name = "_QFparallel_do_with_privatisation_clausesEnt"}
   ! CHECK:    %[[NT_VAL:.*]] = fir.load %[[NT_REF]] : !fir.ref<i32>
   ! CHECK:    fir.store %[[NT_VAL]] to %[[PRIVATE_NT_REF]] : !fir.ref<i32>
-  ! CHECK:    omp.barrier
+  ! CHECK-NOT:omp.barrier
   ! CHECK:    %[[WS_LB:.*]] = arith.constant 1 : i32
   ! CHECK:    %[[WS_UB:.*]] = arith.constant 9 : i32
   ! CHECK:    %[[WS_STEP:.*]] = arith.constant 1 : i32
@@ -138,7 +138,7 @@
 ! CHECK:             %[[NT_ADDR:.*]] = fir.alloca i32 {bindc_name = "nt", pinned, uniq_name = "_QFparallel_private_doEnt"}
 ! CHECK:             %[[NT:.*]] = fir.load %[[VAL_1]] : !fir.ref<i32>
 ! CHECK:             fir.store %[[NT]] to %[[NT_ADDR]] : !fir.ref<i32>
-! CHECK:             omp.barrier
+! CHECK-NOT:         omp.barrier
 ! CHECK:             %[[VAL_7:.*]] = arith.constant 1 : i32
 ! CHECK:             %[[VAL_8:.*]] = arith.constant 9 : i32
 ! CHECK:             %[[VAL_9:.*]] = arith.constant 1 : i32
@@ -153,8 +153,7 @@
 ! CHECK:         }
 
 !===============================================================================
-! Checking for the following construct - multiple firstprivate clauses must emit
-! only one barrier
+! Checking for the following construct
 !   !$omp parallel
 !   !$omp do firstprivate(...) firstprivate(...)
 !===============================================================================
@@ -182,7 +181,7 @@
 ! CHECK:             %[[B_PRIV_ADDR:.*]] = fir.alloca i32 {bindc_name = "b", pinned, uniq_name = "_QFomp_parallel_multiple_firstprivate_doEb"}
 ! CHECK:             %[[B:.*]] = fir.load %[[B_ADDR]] : !fir.ref<i32>
 ! CHECK:             fir.store %[[B]] to %[[B_PRIV_ADDR]] : !fir.ref<i32>
-! CHECK:             omp.barrier
+! CHECK-NOT:         omp.barrier
 ! CHECK:             %[[VAL_8:.*]] = arith.constant 1 : i32
 ! CHECK:             %[[VAL_9:.*]] = arith.constant 10 : i32
 ! CHECK:             %[[VAL_10:.*]] = arith.constant 1 : i32
@@ -224,7 +223,7 @@
 ! CHECK:             %[[NT_ADDR:.*]] = fir.alloca i32 {bindc_name = "nt", pinned, uniq_name = "_QFparallel_do_privateEnt"}
 ! CHECK:             %[[NT:.*]] = fir.load %[[VAL_1]] : !fir.ref<i32>
 ! CHECK:             fir.store %[[NT]] to %[[NT_ADDR]] : !fir.ref<i32>
-! CHECK:             omp.barrier
+! CHECK-NOT:         omp.barrier
 ! CHECK:             %[[I_PRIV_ADDR:.*]] = fir.alloca i32 {adapt.valuebyref, pinned}
 ! CHECK:             %[[VAL_7:.*]] = arith.constant 1 : i32
 ! CHECK:             %[[VAL_8:.*]] = arith.constant 9 : i32
@@ -240,8 +239,7 @@
 ! CHECK:         }
 
 !===============================================================================
-! Checking for the following construct - multiple firstprivate clauses must emit
-! only one barrier
+! Checking for the following construct
 !   !$omp parallel
 !   !$omp do firstprivate(...) firstprivate(...)
 !===============================================================================
@@ -268,7 +266,6 @@
 ! CHECK:             %[[B_PRIV_ADDR:.*]] = fir.alloca i32 {bindc_name = "b", pinned, uniq_name = "_QFomp_parallel_do_multiple_firstprivateEb"}
 ! CHECK:             %[[B:.*]] = fir.load %[[B_ADDR]] : !fir.ref<i32>
 ! CHECK:             fir.store %[[B]] to %[[B_PRIV_ADDR]] : !fir.ref<i32>
-! CHECK:             omp.barrier
 ! CHECK-NOT:         omp.barrier
 ! CHECK:             %[[I_PRIV_ADDR:.*]] = fir.alloca i32 {adapt.valuebyref, pinned}
 ! CHECK:             %[[VAL_8:.*]] = arith.constant 1 : i32