[OpenMP] Lowering parse-tree to MLIR of ordered threads directive

This patch supports lowering parse-tree to MLIR of ordered threads
directive following Section 2.19.9 of the OpenMP 5.1 standard.

Author: PeixinQiao

flang/lib/Lower/OpenMP.cpp

@@ -411,6 +411,21 @@ genOMP(Fortran::lower::AbstractConverter &converter,
     mlir::Location currentLocation = converter.getCurrentLocation();
     auto masterOp = firOpBuilder.create<mlir::omp::MasterOp>(currentLocation);
     createBodyOfOp<omp::MasterOp>(masterOp, converter, currentLocation, eval);
+  } else if (blockDirective.v == llvm::omp::OMPD_ordered) {
+    auto &firOpBuilder = converter.getFirOpBuilder();
+    auto currentLocation = converter.getCurrentLocation();
+    mlir::Attribute simdClauseOperand;
+    auto orderedOp = firOpBuilder.create<mlir::omp::OrderedRegionOp>(
+        currentLocation, simdClauseOperand.dyn_cast_or_null<UnitAttr>());
+    const auto &clauseList =
+        std::get<Fortran::parser::OmpClauseList>(beginBlockDirective.t);
+    for (const auto &clause : clauseList.v) {
+      if (std::get_if<Fortran::parser::OmpClause::Simd>(&clause.u)) {
+        TODO(currentLocation, "OpenMP ORDERED SIMD");
+      }
+    }
+    createBodyOfOp<omp::OrderedRegionOp>(orderedOp, converter, currentLocation,
+                                         eval);
   }
 }
 

flang/test/Lower/OpenMP/omp-ordered-threads.f90

@@ -0,0 +1,42 @@
+! This test checks lowering of OpenMP ordered directive with threads Clause.
+! Without clause in ordered direcitve, it behaves as if threads clause is
+! specified.
+
+! RUN: bbc -fopenmp -emit-fir %s -o - | FileCheck %s --check-prefix=FIRDialect
+! RUN: bbc -fopenmp -emit-fir %s -o - | \
+! RUN:   tco --disable-llvm --print-ir-after=fir-to-llvm-ir 2>&1 | \
+! RUN:   FileCheck %s --check-prefix=LLVMIRDialect
+! RUN: bbc -fopenmp -emit-fir %s -o - | tco | FileCheck %s --check-prefix=LLVMIR
+
+program ordered
+        integer :: i
+        integer :: a(20)
+
+!FIRDialect: omp.ordered_region  {
+!LLVMIRDialect: omp.ordered_region  {
+!LLVMIR: [[TMP0:%.*]] = call i32 @__kmpc_global_thread_num(%struct.ident_t* @[[GLOB0:[0-9]+]]), !dbg !{{.*}}
+!LLVMIR-NEXT: call void @__kmpc_ordered(%struct.ident_t* @[[GLOB0]], i32 [[TMP0]]), !dbg !{{.*}}
+!$OMP ORDERED
+        a(i) = a(i-1) + 1
+!FIRDialect:   omp.terminator
+!FIRDialect-NEXT: }
+!LLVMIRDialect:   omp.terminator
+!LLVMIRDialect-NEXT: }
+!LLVMIR: call void @__kmpc_end_ordered(%struct.ident_t* @[[GLOB0]], i32 [[TMP0]]), !dbg !{{.*}}
+!$OMP END ORDERED
+
+!FIRDialect: omp.ordered_region  {
+!LLVMIRDialect: omp.ordered_region  {
+!LLVMIR: [[TMP1:%.*]] = call i32 @__kmpc_global_thread_num(%struct.ident_t* @[[GLOB1:[0-9]+]]), !dbg !{{.*}}
+!LLVMIR-NEXT: call void @__kmpc_ordered(%struct.ident_t* @[[GLOB1]], i32 [[TMP1]]), !dbg !{{.*}}
+!$OMP ORDERED THREADS
+        a(i) = a(i-1) + 1
+!FIRDialect:   omp.terminator
+!FIRDialect-NEXT: }
+!LLVMIRDialect:   omp.terminator
+!LLVMIRDialect-NEXT: }
+!LLVMIR: call void @__kmpc_end_ordered(%struct.ident_t* @[[GLOB1]], i32 [[TMP1]]), !dbg !{{.*}}
+!LLVMIR-NEXT: ret void, !dbg !{{.*}}
+!$OMP END ORDERED
+
+end