[flang-commits] [flang] [flang][OpenMP] Support reduction of variables in EQUIVALENCE (PR #130607)

[Tom Eccles via flang-commits]

https://github.com/tblah created https://github.com/llvm/llvm-project/pull/130607

These previously crashed the compiler because !fir.ptr (not wrapped inside of a box) was not supported.

Real POINTER variables are supported as !fir.box<!fir.ptr<>>. The version for EQUIVALENCE doesn't need to do anything different to !fir.ref<>.

>From 3bd6f005b48bd876992c6fa9fc33e2d07445ac63 Mon Sep 17 00:00:00 2001
From: Tom Eccles <tom.eccles at arm.com>
Date: Mon, 10 Mar 2025 13:46:14 +0000
Subject: [PATCH] [flang][OpenMP] Support reduction of variables in EQUIVALENCE

These previously crashed the compiler because !fir.ptr (not wrapped
inside of a box) was not supported.

Real POINTER variables are supported as !fir.box<!fir.ptr<>>. The
version for EQUIVALENCE doesn't need to do anything different to
!fir.ref<>.
---
 flang/lib/Lower/OpenMP/ReductionProcessor.cpp |  9 ++--
 .../Lower/OpenMP/reduction-equivalence.f90    | 48 +++++++++++++++++++
 2 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 flang/test/Lower/OpenMP/reduction-equivalence.f90

diff --git a/flang/lib/Lower/OpenMP/ReductionProcessor.cpp b/flang/lib/Lower/OpenMP/ReductionProcessor.cpp
index f83079eb68688..aa1187669ca8b 100644
--- a/flang/lib/Lower/OpenMP/ReductionProcessor.cpp
+++ b/flang/lib/Lower/OpenMP/ReductionProcessor.cpp
@@ -617,10 +617,13 @@ void ReductionProcessor::processReductionArguments(
     // this isn't the same as the by-val and by-ref passing later in the
     // pipeline. Both styles assume that the variable is a reference at
     // this point
-    assert(mlir::isa<fir::ReferenceType>(symVal.getType()) &&
-           "reduction input var is a reference");
+    assert(fir::isa_ref_type(symVal.getType()) &&
+           "reduction input var is passed by reference");
+    mlir::Type elementType = fir::dyn_cast_ptrEleTy(symVal.getType());
+    mlir::Type refTy = fir::ReferenceType::get(elementType);
 
-    reductionVars.push_back(symVal);
+    reductionVars.push_back(
+        builder.createConvert(currentLocation, refTy, symVal));
     reduceVarByRef.push_back(doReductionByRef(symVal));
   }
 
diff --git a/flang/test/Lower/OpenMP/reduction-equivalence.f90 b/flang/test/Lower/OpenMP/reduction-equivalence.f90
new file mode 100644
index 0000000000000..f46e148ac61cd
--- /dev/null
+++ b/flang/test/Lower/OpenMP/reduction-equivalence.f90
@@ -0,0 +1,48 @@
+! RUN: bbc -emit-hlfir -fopenmp -o - %s | FileCheck %s
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -o - %s | FileCheck %s
+
+! Test that we can reduce variables used in an equivalence statement.
+! Unlike POINTER variables these are lowered to an unboxed !fir.ptr<>.
+
+subroutine reduction_equivalence()
+  integer::va
+  equivalence (va,vva)
+  va=1
+
+!$omp parallel reduction(+:va)
+  va=1
+!$omp end parallel
+end subroutine reduction_equivalence
+
+
+! CHECK-LABEL:   omp.declare_reduction @add_reduction_i32 : i32 init {
+! CHECK:         ^bb0(%[[VAL_0:.*]]: i32):
+! CHECK:           %[[VAL_1:.*]] = arith.constant 0 : i32
+! CHECK:           omp.yield(%[[VAL_1]] : i32)
+! CHECK-LABEL:   } combiner {
+! CHECK:         ^bb0(%[[VAL_0:.*]]: i32, %[[VAL_1:.*]]: i32):
+! CHECK:           %[[VAL_2:.*]] = arith.addi %[[VAL_0]], %[[VAL_1]] : i32
+! CHECK:           omp.yield(%[[VAL_2]] : i32)
+! CHECK:         }
+
+! CHECK-LABEL:   func.func @_QPreduction_equivalence() {
+! CHECK:           %[[VAL_0:.*]] = fir.alloca !fir.array<4xi8> {uniq_name = "_QFreduction_equivalenceEva"}
+! CHECK:           %[[VAL_1:.*]] = arith.constant 0 : index
+! CHECK:           %[[VAL_2:.*]] = fir.coordinate_of %[[VAL_0]], %[[VAL_1]] : (!fir.ref<!fir.array<4xi8>>, index) -> !fir.ref<i8>
+! CHECK:           %[[VAL_3:.*]] = fir.convert %[[VAL_2]] : (!fir.ref<i8>) -> !fir.ptr<i32>
+! CHECK:           %[[VAL_4:.*]]:2 = hlfir.declare %[[VAL_3]] {uniq_name = "_QFreduction_equivalenceEva"} : (!fir.ptr<i32>) -> (!fir.ptr<i32>, !fir.ptr<i32>)
+! CHECK:           %[[VAL_5:.*]] = arith.constant 0 : index
+! CHECK:           %[[VAL_6:.*]] = fir.coordinate_of %[[VAL_0]], %[[VAL_5]] : (!fir.ref<!fir.array<4xi8>>, index) -> !fir.ref<i8>
+! CHECK:           %[[VAL_7:.*]] = fir.convert %[[VAL_6]] : (!fir.ref<i8>) -> !fir.ptr<f32>
+! CHECK:           %[[VAL_8:.*]]:2 = hlfir.declare %[[VAL_7]] {uniq_name = "_QFreduction_equivalenceEvva"} : (!fir.ptr<f32>) -> (!fir.ptr<f32>, !fir.ptr<f32>)
+! CHECK:           %[[VAL_9:.*]] = arith.constant 1 : i32
+! CHECK:           hlfir.assign %[[VAL_9]] to %[[VAL_4]]#0 : i32, !fir.ptr<i32>
+! CHECK:           %[[VAL_10:.*]] = fir.convert %[[VAL_4]]#0 : (!fir.ptr<i32>) -> !fir.ref<i32>
+! CHECK:           omp.parallel reduction(@add_reduction_i32 %[[VAL_10]] -> %[[VAL_11:.*]] : !fir.ref<i32>) {
+! CHECK:             %[[VAL_12:.*]]:2 = hlfir.declare %[[VAL_11]] {uniq_name = "_QFreduction_equivalenceEva"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:             %[[VAL_13:.*]] = arith.constant 1 : i32
+! CHECK:             hlfir.assign %[[VAL_13]] to %[[VAL_12]]#0 : i32, !fir.ref<i32>
+! CHECK:             omp.terminator
+! CHECK:           }
+! CHECK:           return
+! CHECK:         }