[flang][OpenMP] Added parallel sections translation

[shraiysh]

Summary

This patch adds translation for parallel sections from PFT to MLIR.

[kiranchandramohan]

LGTM. Would be great if @NimishMishra could also have a look.

[NimishMishra]

Thanks @shraiysh for this.

LGTM

flang/lib/Lower/OpenMP.cpp

genOMP(Fortran::lower::AbstractConverter &converter,
   const auto &clauseList =
       std::get<Fortran::parser::OmpClauseList>(endSectionsClauseList.t);
   for (const auto &clause : clauseList.v) {
     if (std::get_if<Fortran::parser::OmpClause::Nowait>(&clause.u)) {
       noWaitClauseOperand = firOpBuilder.getUnitAttr();
     }
   }
 
-  mlir::omp::SectionsOp sectionsOp = firOpBuilder.create<mlir::omp::SectionsOp>(
+  llvm::omp::Directive dir =
+      std::get<Fortran::parser::OmpSectionsDirective>(
+          std::get<Fortran::parser::OmpBeginSectionsDirective>(
+              sectionsConstruct.t)
+              .t)
+          .v;
+
+  // Parallel Sections Construct
+  if (dir == llvm::omp::Directive::OMPD_parallel_sections) {
+    // TODO: add reduction support once omp.parallel supports it.
+    auto parallelOp = firOpBuilder.create<mlir::omp::ParallelOp>(
+        currentLocation, /*if_expr_var*/ nullptr, /*num_threads_var*/ nullptr,
+        allocateOperands, allocatorOperands, /*proc_bind_val*/ nullptr);
+    createBodyOfOp(parallelOp, firOpBuilder, currentLocation);
+    auto sectionsOp = firOpBuilder.create<mlir::omp::SectionsOp>(
+        currentLocation, /*reduction_vars*/ ValueRange(),
+        /*reductions=*/nullptr, /*allocate_vars*/ ValueRange(),
+        /*allocators_vars*/ ValueRange(), /*nowait=*/nullptr);
+    createBodyOfOp(sectionsOp, firOpBuilder, currentLocation);
+
+    // Sections Construct
+  } else if (dir == llvm::omp::Directive::OMPD_sections) {
+    auto sectionsOp = firOpBuilder.create<mlir::omp::SectionsOp>(
         currentLocation, reductionVars, /*reductions = */ nullptr,
         allocateOperands, allocatorOperands, noWaitClauseOperand);
-
     createBodyOfOp<omp::SectionsOp>(sectionsOp, firOpBuilder, currentLocation);
   }
+}
 
 void Fortran::lower::genOpenMPConstruct(
     Fortran::lower::AbstractConverter &converter,
     Fortran::lower::pft::Evaluation &eval,
     const Fortran::parser::OpenMPConstruct &ompConstruct) {
 
   std::visit(
       common::visitors{

flang/test/Lower/OpenMP/parallel-sections.f90

+!RUN: %flang_fc1 -emit-fir -fopenmp %s -o - | FileCheck %s --check-prefixes="FIRDialect,OMPDialect"
+!RUN: %flang_fc1 -emit-fir -fopenmp %s -o - | fir-opt --cfg-conversion | fir-opt --fir-to-llvm-ir | FileCheck %s --check-prefixes="OMPDialect,LLVMDialect"
+
+!===============================================================================
+! Parallel sections construct
+!===============================================================================
+
+!FIRDialect: func @_QPomp_parallel_sections
+subroutine omp_parallel_sections(x, y)
+  integer, intent(inout) :: x, y
+  !OMPDialect: omp.parallel {
+  !OMPDialect: omp.sections {
+  !$omp parallel sections
+    !OMPDialect: omp.section {
+    !$omp section
+      !FIRDialect: fir.load
+      !FIRDialect: arith.addi
+      !FIRDialect: fir.store
+      x = x + 12
+      !OMPDialect: omp.terminator
+    !OMPDialect: omp.section {
+    !$omp section
+      !FIRDialect: fir.load
+      !FIRDialect: arith.subi
+      !FIRDialect: fir.store
+      y = y - 5
+      !OMPDialect: omp.terminator
+  !OMPDialect: omp.terminator
+  !OMPDialect: omp.terminator
+  !$omp end parallel sections
+end subroutine omp_parallel_sections
+
+!===============================================================================
+! Parallel sections construct with allocate clause
+!===============================================================================
+
+!FIRDialect: func @_QPomp_parallel_sections
+subroutine omp_parallel_sections_allocate(x, y)
+  use omp_lib
+  integer, intent(inout) :: x, y
+  !FIRDialect: %[[allocator:.*]] = arith.constant 1 : i32
+  !LLVMDialect: %[[allocator:.*]] = llvm.mlir.constant(1 : i32) : i32
+  !OMPDialect: omp.parallel allocate(%[[allocator]] : i32 -> %{{.*}} : !fir.ref<i32>) {
+  !OMPDialect: omp.sections {
+  !$omp parallel sections allocate(omp_high_bw_mem_alloc: x)
+    !OMPDialect: omp.section {
+    !$omp section
+      x = x + 12
+      !OMPDialect: omp.terminator
+    !OMPDialect: omp.section {
+    !$omp section
+      y = y + 5
+      !OMPDialect: omp.terminator
+  !OMPDialect: omp.terminator
+  !OMPDialect: omp.terminator
+  !$omp end parallel sections
+end subroutine omp_parallel_sections_allocate