From a87033582f1abacba862cea555d400a73426c81d Mon Sep 17 00:00:00 2001
From: Jack Styles <jack.styles@arm.com>
Date: Fri, 7 Nov 2025 10:52:28 +0000
Subject: [PATCH] [Flang][OpenMP] Add support for `taskloop nogroup` Lowering

NoGroup is a clause that is supported by taskloop in the OpenMP
standards. Until this point, this has been marked as TODO as
support was not present in AST->FIR lowering. This has now been
added so the clause can be emitted in HLFIR/FIR. Lowering from FIR to
LLVM IR is not available as this has not been completed for taskloop.
---
 flang/lib/Lower/OpenMP/ClauseProcessor.cpp   |  5 ++++
 flang/lib/Lower/OpenMP/ClauseProcessor.h     |  1 +
 flang/lib/Lower/OpenMP/OpenMP.cpp            |  7 +++---
 flang/test/Lower/OpenMP/taskloop-nogroup.f90 | 25 ++++++++++++++++++++
 4 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 flang/test/Lower/OpenMP/taskloop-nogroup.f90

diff --git a/flang/lib/Lower/OpenMP/ClauseProcessor.cpp b/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
index 1c163e6de7e5a..872f31fe45cca 100644
--- a/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
+++ b/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
@@ -406,6 +406,11 @@ bool ClauseProcessor::processMergeable(
   return markClauseOccurrence<omp::clause::Mergeable>(result.mergeable);
 }
 
+bool ClauseProcessor::processNogroup(
+    mlir::omp::NogroupClauseOps &result) const {
+  return markClauseOccurrence<omp::clause::Nogroup>(result.nogroup);
+}
+
 bool ClauseProcessor::processNowait(mlir::omp::NowaitClauseOps &result) const {
   return markClauseOccurrence<omp::clause::Nowait>(result.nowait);
 }
diff --git a/flang/lib/Lower/OpenMP/ClauseProcessor.h b/flang/lib/Lower/OpenMP/ClauseProcessor.h
index 6452e39b97551..d524b4ddc8ac4 100644
--- a/flang/lib/Lower/OpenMP/ClauseProcessor.h
+++ b/flang/lib/Lower/OpenMP/ClauseProcessor.h
@@ -89,6 +89,7 @@ class ClauseProcessor {
   bool processInclusive(mlir::Location currentLocation,
                         mlir::omp::InclusiveClauseOps &result) const;
   bool processMergeable(mlir::omp::MergeableClauseOps &result) const;
+  bool processNogroup(mlir::omp::NogroupClauseOps &result) const;
   bool processNowait(mlir::omp::NowaitClauseOps &result) const;
   bool processNumTasks(lower::StatementContext &stmtCtx,
                        mlir::omp::NumTasksClauseOps &result) const;
diff --git a/flang/lib/Lower/OpenMP/OpenMP.cpp b/flang/lib/Lower/OpenMP/OpenMP.cpp
index ad456d89bc432..36814f27029b7 100644
--- a/flang/lib/Lower/OpenMP/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP/OpenMP.cpp
@@ -1771,13 +1771,14 @@ static void genTaskloopClauses(lower::AbstractConverter &converter,
 
   ClauseProcessor cp(converter, semaCtx, clauses);
   cp.processGrainsize(stmtCtx, clauseOps);
+  cp.processNogroup(clauseOps);
   cp.processNumTasks(stmtCtx, clauseOps);
 
   cp.processTODO<clause::Allocate, clause::Collapse, clause::Default,
                  clause::Final, clause::If, clause::InReduction,
-                 clause::Lastprivate, clause::Mergeable, clause::Nogroup,
-                 clause::Priority, clause::Reduction, clause::Shared,
-                 clause::Untied>(loc, llvm::omp::Directive::OMPD_taskloop);
+                 clause::Lastprivate, clause::Mergeable, clause::Priority,
+                 clause::Reduction, clause::Shared, clause::Untied>(
+      loc, llvm::omp::Directive::OMPD_taskloop);
 }
 
 static void genTaskwaitClauses(lower::AbstractConverter &converter,
diff --git a/flang/test/Lower/OpenMP/taskloop-nogroup.f90 b/flang/test/Lower/OpenMP/taskloop-nogroup.f90
new file mode 100644
index 0000000000000..d2c7aa5202b39
--- /dev/null
+++ b/flang/test/Lower/OpenMP/taskloop-nogroup.f90
@@ -0,0 +1,25 @@
+! Test the Nogroup clause when used with the taskloop directive
+! RUN: bbc -emit-hlfir -fopenmp -fopenmp-version=45 %s -o - 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=45 %s -o - 2>&1 | FileCheck %s
+
+! CHECK-LABEL: omp.private
+! CHECK-SAME: {type = private} @[[I_PRIVATE:.*]] : i32
+! CHECK-LABEL: omp.private
+! CHECK-SAME: {type = firstprivate} @[[SUM_FIRSTPRIVATE:.*]] : i32 copy
+
+! CHECK: %[[ALLOCA_I:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QFtestEi"}
+! CHECK: %[[DECLARE_I:.*]]:2 = hlfir.declare %[[ALLOCA_I]] {uniq_name = "_QFtestEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: %[[ALLOCA_SUM:.*]] = fir.alloca i32 {bindc_name = "sum", uniq_name = "_QFtestEsum"}
+! CHECK: %[[DECLARE_SUM:.*]]:2 = hlfir.declare %[[ALLOCA_SUM]] {uniq_name = "_QFtestEsum"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+
+subroutine test()
+    integer :: i, sum
+
+    ! CHECK-LABEL: omp.taskloop
+    ! CHECK-SAME: nogroup private(@_QFtestEsum_firstprivate_i32 %[[DECLARE_SUM]]#0 -> %arg0, @_QFtestEi_private_i32 %[[DECLARE_I]]#0 -> %arg1 : !fir.ref<i32>, !fir.ref<i32>)
+    !$omp taskloop nogroup
+    do i=1,10
+        sum = sum + i
+    end do
+    !$omp end taskloop
+end subroutine