[flang][openacc] Generate loop nest as column major

Address comment from D153455

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D153650

flang/lib/Lower/OpenACC.cpp

@@ -647,7 +647,7 @@ static mlir::Value genCombiner(fir::FirOpBuilder &builder, mlir::Location loc,
 
       llvm::SmallVector<fir::DoLoopOp> loops;
       llvm::SmallVector<mlir::Value> ivs;
-      for (auto ext : seqTy.getShape()) {
+      for (auto ext : llvm::reverse(seqTy.getShape())) {
         auto lb = builder.create<mlir::arith::ConstantOp>(
             loc, idxTy, builder.getIntegerAttr(idxTy, 0));
         auto ub = builder.create<mlir::arith::ConstantOp>(

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

@@ -123,15 +123,15 @@
 ! CHECK: } combiner {
 ! CHECK: ^bb0(%[[ARG0:.*]]: !fir.ref<!fir.array<100x10x2xi32>>, %[[ARG1:.*]]: !fir.ref<!fir.array<100x10x2xi32>>):
 ! CHECK:   %[[LB0:.*]] = arith.constant 0 : index
-! CHECK:   %[[UB0:.*]] = arith.constant 99 : 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 1 : index
+! CHECK:       %[[UB2:.*]] = arith.constant 99 : index
 ! CHECK:       %[[STEP2:.*]] = arith.constant 1 : index
 ! CHECK:       fir.do_loop %[[IV2:.*]] = %[[LB2]] to %[[UB2]] step %[[STEP2]] {
 ! CHECK:         %[[COORD1:.*]] = fir.coordinate_of %[[ARG0]], %[[IV0]], %[[IV1]], %[[IV2]] : (!fir.ref<!fir.array<100x10x2xi32>>, index, index, index) -> !fir.ref<i32>
@@ -153,11 +153,11 @@
 ! CHECK: } combiner {
 ! CHECK: ^bb0(%[[ARG0:.*]]: !fir.ref<!fir.array<100x10xi32>>, %[[ARG1:.*]]: !fir.ref<!fir.array<100x10xi32>>):
 ! CHECK:   %[[LB0:.*]] = arith.constant 0 : index
-! CHECK:   %[[UB0:.*]] = arith.constant 99 : index
+! CHECK:   %[[UB0:.*]] = arith.constant 9 : 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:     %[[UB1:.*]] = arith.constant 99 : index
 ! CHECK:     %[[STEP1:.*]] = arith.constant 1 : index
 ! CHECK:     fir.do_loop %[[IV1:.*]] = %[[LB1]] to %[[UB1]] step %[[STEP1]] {
 ! CHECK:       %[[COORD1:.*]] = fir.coordinate_of %[[ARG0]], %[[IV0]], %[[IV1]] : (!fir.ref<!fir.array<100x10xi32>>, index, index) -> !fir.ref<i32>