[flang][acc] Fix the indexing of the reduction initializer for multidimensional static arrays (#159848)

Similarly to llvm/llvm-project#155536, this PR
fixes incorrect coordinates for array access in the reduction
initializer.

Author: khaki3

flang/lib/Optimizer/OpenACC/Support/FIROpenACCTypeInterfaces.cpp

@@ -587,6 +587,8 @@ mlir::Value OpenACCMappableModel<Ty>::generatePrivateInit(
             loops.push_back(loop);
             ivs.push_back(loop.getInductionVar());
           }
+          // Reverse IVs to match CoordinateOp's canonical index order.
+          std::reverse(ivs.begin(), ivs.end());
           auto coord = fir::CoordinateOp::create(firBuilder, loc, refTy,
                                                  declareOp.getBase(), ivs);
           fir::StoreOp::create(firBuilder, loc, initVal, coord);

flang/test/Lower/OpenACC/acc-reduction-unwrap-defaultbounds.f90

@@ -597,6 +597,20 @@
 ! CHECK:   %[[SHAPE:.*]] = fir.shape %{{.*}}, %{{.*}}, %{{.*}} : (index, index, index) -> !fir.shape<3>
 ! CHECK:   %[[ALLOCA:.*]] = fir.alloca !fir.array<100x10x2xi32>
 ! CHECK:   %[[DECLARE:.*]]:2 = hlfir.declare %[[ALLOCA]](%[[SHAPE]]) {uniq_name = "acc.reduction.init"} : (!fir.ref<!fir.array<100x10x2xi32>>, !fir.shape<3>) -> (!fir.ref<!fir.array<100x10x2xi32>>, !fir.ref<!fir.array<100x10x2xi32>>)
+! CHECK:   %[[LB0:.*]] = arith.constant 0 : index
+! CHECK:   %[[UB0:.*]] = arith.constant 1 : index
+! CHECK:   %[[STEP0:.*]] = arith.constant 1 : index
+! CHECK:   fir.do_loop %[[IV0:.*]] = %[[LB0]] to %[[UB0]] step %[[STEP0]] {
+! CHECK:     %[[LB1:.*]] = arith.constant 0 : index
+! CHECK:     %[[UB1:.*]] = arith.constant 9 : index
+! CHECK:     %[[STEP1:.*]] = arith.constant 1 : index
+! CHECK:     fir.do_loop %[[IV1:.*]] = %[[LB1]] to %[[UB1]] step %[[STEP1]] {
+! CHECK:       %[[LB2:.*]] = arith.constant 0 : index
+! CHECK:       %[[UB2:.*]] = arith.constant 99 : index
+! CHECK:       %[[STEP2:.*]] = arith.constant 1 : index
+! CHECK:       fir.do_loop %[[IV2:.*]] = %[[LB2]] to %[[UB2]] step %[[STEP2]] {
+! CHECK:         %[[COORD]] = fir.coordinate_of %[[DECLARE]]#0, %[[IV2]], %[[IV1]], %[[IV0]] : (!fir.ref<!fir.array<100x10x2xi32>>, index, index, index) -> !fir.ref<i32>
+! CHECK:         fir.store %[[INIT]] to %[[COORD]] : !fir.ref<i32>
 ! CHECK:   acc.yield %[[DECLARE]]#0 : !fir.ref<!fir.array<100x10x2xi32>>
 ! CHECK: } combiner {
 ! CHECK: ^bb0(%[[ARG0:.*]]: !fir.ref<!fir.array<100x10x2xi32>>, %[[ARG1:.*]]: !fir.ref<!fir.array<100x10x2xi32>>):

flang/test/Lower/OpenACC/acc-reduction.f90

@@ -646,6 +646,20 @@
 ! CHECK:   %[[SHAPE:.*]] = fir.shape %{{.*}}, %{{.*}}, %{{.*}} : (index, index, index) -> !fir.shape<3>
 ! CHECK:   %[[ALLOCA:.*]] = fir.alloca !fir.array<100x10x2xi32>
 ! CHECK:   %[[DECLARE:.*]]:2 = hlfir.declare %[[ALLOCA]](%[[SHAPE]]) {uniq_name = "acc.reduction.init"} : (!fir.ref<!fir.array<100x10x2xi32>>, !fir.shape<3>) -> (!fir.ref<!fir.array<100x10x2xi32>>, !fir.ref<!fir.array<100x10x2xi32>>)
+! CHECK:   %[[LB0:.*]] = arith.constant 0 : index
+! CHECK:   %[[UB0:.*]] = arith.constant 1 : index
+! CHECK:   %[[STEP0:.*]] = arith.constant 1 : index
+! CHECK:   fir.do_loop %[[IV0:.*]] = %[[LB0]] to %[[UB0]] step %[[STEP0]] {
+! CHECK:     %[[LB1:.*]] = arith.constant 0 : index
+! CHECK:     %[[UB1:.*]] = arith.constant 9 : index
+! CHECK:     %[[STEP1:.*]] = arith.constant 1 : index
+! CHECK:     fir.do_loop %[[IV1:.*]] = %[[LB1]] to %[[UB1]] step %[[STEP1]] {
+! CHECK:       %[[LB2:.*]] = arith.constant 0 : index
+! CHECK:       %[[UB2:.*]] = arith.constant 99 : index
+! CHECK:       %[[STEP2:.*]] = arith.constant 1 : index
+! CHECK:       fir.do_loop %[[IV2:.*]] = %[[LB2]] to %[[UB2]] step %[[STEP2]] {
+! CHECK:         %[[COORD]] = fir.coordinate_of %[[DECLARE]]#0, %[[IV2]], %[[IV1]], %[[IV0]] : (!fir.ref<!fir.array<100x10x2xi32>>, index, index, index) -> !fir.ref<i32>
+! CHECK:         fir.store %[[INIT]] to %[[COORD]] : !fir.ref<i32>
 ! CHECK:   acc.yield %[[DECLARE]]#0 : !fir.ref<!fir.array<100x10x2xi32>>
 ! CHECK: } combiner {
 ! CHECK: ^bb0(%[[ARG0:.*]]: !fir.ref<!fir.array<100x10x2xi32>>, %[[ARG1:.*]]: !fir.ref<!fir.array<100x10x2xi32>>):