[flang][OpenMP] Added support for lowering OpenMP barrier construct

flang/include/flang/Lower/OpenMP.h

@@ -12,6 +12,8 @@
 namespace Fortran {
 namespace parser {
 struct OpenMPConstruct;
+struct OpenMPStandaloneConstruct;
+struct OpenMPSimpleStandaloneConstruct;
 struct OmpEndLoopDirective;
 } // namespace parser
 
@@ -26,6 +28,12 @@ struct Evaluation;
 void genOpenMPConstruct(AbstractConverter &, pft::Evaluation &,
                         const parser::OpenMPConstruct &);
 
+void genOMP(AbstractConverter &, pft::Evaluation &,
+            const parser::OpenMPStandaloneConstruct &);
+
+void genOMP(AbstractConverter &, pft::Evaluation &,
+            const parser::OpenMPSimpleStandaloneConstruct &);
+
 void genOpenMPEndLoop(AbstractConverter &, pft::Evaluation &,
                       const parser::OmpEndLoopDirective &);
 

flang/include/flang/Optimizer/Dialect/FIRDialect.h

@@ -46,6 +46,7 @@ inline void registerFIR() {
     mlir::registerDialect<mlir::StandardOpsDialect>();
     mlir::registerDialect<mlir::vector::VectorDialect>();
     mlir::registerDialect<FIROpsDialect>();
+    mlir::registerDialect<mlir::omp::OpenMPDialect>();
     return true;
   }();
 }

flang/lib/Lower/OpenMP.cpp

@@ -8,15 +8,90 @@
 
 #include "flang/Lower/OpenMP.h"
 #include "flang/Lower/Bridge.h"
+#include "flang/Lower/FIRBuilder.h"
 #include "flang/Lower/PFTBuilder.h"
 #include "flang/Parser/parse-tree.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
 
 #define TODO() llvm_unreachable("not yet implemented")
 
+void Fortran::lower::genOMP(
+    Fortran::lower::AbstractConverter &absConv,
+    Fortran::lower::pft::Evaluation &eval,
+    const Fortran::parser::OpenMPSimpleStandaloneConstruct
+        &simpleStandaloneConstruct) {
+  const auto &directive =
+      std::get<Fortran::parser::OmpSimpleStandaloneDirective>(
+          simpleStandaloneConstruct.t);
+  switch (directive.v) {
+
+  case parser::OmpSimpleStandaloneDirective::Directive::Barrier:
+    absConv.getFirOpBuilder().create<mlir::omp::BarrierOp>(
+        absConv.getCurrentLocation());
+    break;
+  case parser::OmpSimpleStandaloneDirective::Directive::Taskwait:
+    TODO();
+  case parser::OmpSimpleStandaloneDirective::Directive::Taskyield:
+    TODO();
+  case parser::OmpSimpleStandaloneDirective::Directive::TargetEnterData:
+    TODO();
+  case parser::OmpSimpleStandaloneDirective::Directive::TargetExitData:
+    TODO();
+  case parser::OmpSimpleStandaloneDirective::Directive::TargetUpdate:
+    TODO();
+  case parser::OmpSimpleStandaloneDirective::Directive::Ordered:
+    TODO();
+  }
+}
+
+void Fortran::lower::genOMP(
+    Fortran::lower::AbstractConverter &absConv,
+    Fortran::lower::pft::Evaluation &eval,
+    const Fortran::parser::OpenMPStandaloneConstruct &standaloneConstruct) {
+  std::visit(
+      common::visitors{
+          [&](const Fortran::parser::OpenMPSimpleStandaloneConstruct
+                  &simpleStandaloneConstruct) {
+            genOMP(absConv, eval, simpleStandaloneConstruct);
+          },
+          [&](const Fortran::parser::OpenMPFlushConstruct &flushConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenMPCancelConstruct &cancelConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenMPCancellationPointConstruct
+                  &cancellationPointConstruct) { TODO(); },
+      },
+      standaloneConstruct.u);
+}
+
 void Fortran::lower::genOpenMPConstruct(
-    Fortran::lower::AbstractConverter &, Fortran::lower::pft::Evaluation &,
-    const Fortran::parser::OpenMPConstruct &) {
-  TODO();
+    Fortran::lower::AbstractConverter &absConv,
+    Fortran::lower::pft::Evaluation &eval,
+    const Fortran::parser::OpenMPConstruct &ompConstruct) {
+
+  std::visit(
+      common::visitors{
+          [&](const Fortran::parser::OpenMPStandaloneConstruct
+                  &standaloneConstruct) {
+            genOMP(absConv, eval, standaloneConstruct);
+          },
+          [&](const Fortran::parser::OpenMPSectionsConstruct
+                  &sectionsConstruct) { TODO(); },
+          [&](const Fortran::parser::OpenMPLoopConstruct &loopConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenMPBlockConstruct &blockConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenMPAtomicConstruct &atomicConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenMPCriticalConstruct
+                  &criticalConstruct) { TODO(); },
+      },
+      ompConstruct.u);
 }
 
 void Fortran::lower::genOpenMPEndLoop(

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -2697,6 +2697,7 @@ struct FIRToLLVMLoweringPass
     mlir::populateStdToLLVMConversionPatterns(typeConverter, pattern);
     mlir::ConversionTarget target{*context};
     target.addLegalDialect<mlir::LLVM::LLVMDialect>();
+    target.addLegalDialect<mlir::omp::OpenMPDialect>();
 
     // required NOPs for applying a full conversion
     target.addLegalOp<mlir::ModuleOp, mlir::ModuleTerminatorOp>();

flang/test/Lower/omp-barrier.f90

@@ -0,0 +1,24 @@
+! This test checks lowering of OpenMP Barrier Directive.
+
+! RUN: bbc -fopenmp -emit-fir %s -o - | \
+! RUN:   FileCheck %s --check-prefix=FIRDialect
+! RUN: bbc -fopenmp -emit-llvm %s -o - | \
+! RUN:   FileCheck %s --check-prefix=LLVMIRDialect
+! RUN: bbc -fopenmp -emit-fir %s -o - | \
+! RUN:   tco | FileCheck %s --check-prefix=LLVMIR
+
+program barrier
+
+        integer :: a,b,c
+
+!$OMP BARRIER
+!FIRDialect: omp.barrier
+!LLVMIRDialect: omp.barrier
+!LLVMIR: call void @__kmpc_barrier(%struct.ident_t* @1, i32 %omp_global_thread_num)
+        c = a + b
+!$OMP BARRIER
+!FIRDialect: omp.barrier
+!LLVMIRDialect: omp.barrier
+!LLVMIR: call void @__kmpc_barrier(%struct.ident_t* @1, i32 %omp_global_thread_num1)
+
+end program