[flang] prevent legacy lowering from being called in pointer assignment (#81750)

When doing a pointer assignment with an RHS that is an array section,
the code fell in the legacy lowering code even with HLFIR enabled.
Escape this old code when HLFIR is on.

Should fix #80884.

Author: jeanPerier

flang/lib/Lower/Bridge.cpp

@@ -3419,6 +3419,13 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       fir::factory::disassociateMutableBox(*builder, loc, lhs);
       return;
     }
+    if (lowerToHighLevelFIR()) {
+      fir::ExtendedValue rhs = genExprAddr(assign.rhs, stmtCtx);
+      fir::factory::associateMutableBoxWithRemap(*builder, loc, lhs, rhs,
+                                                 lbounds, ubounds);
+      return;
+    }
+    // Legacy lowering below.
     // Do not generate a temp in case rhs is an array section.
     fir::ExtendedValue rhs =
         Fortran::lower::isArraySectionWithoutVectorSubscript(assign.rhs)
@@ -3427,7 +3434,7 @@ class FirConverter : public Fortran::lower::AbstractConverter {
             : genExprAddr(assign.rhs, stmtCtx);
     fir::factory::associateMutableBoxWithRemap(*builder, loc, lhs, rhs, lbounds,
                                                ubounds);
-    if (!lowerToHighLevelFIR() && explicitIterationSpace()) {
+    if (explicitIterationSpace()) {
       mlir::ValueRange inners = explicitIterSpace.getInnerArgs();
       if (!inners.empty())
         builder->create<fir::ResultOp>(loc, inners);

flang/test/Lower/HLFIR/issue80884.f90

@@ -0,0 +1,32 @@
+! Test lowering of pointer remapping with component ref in the RHS.
+! RUN: bbc -emit-hlfir -o - %s -I nw | FileCheck %s
+
+subroutine issue80884(p, targ)
+  type t0
+    real :: array(10, 10)
+  end type
+  type, extends(t0) :: t
+  end type
+  type(t), target :: targ
+  real, pointer :: p(:)
+  p(1:100) => targ%array
+end subroutine
+! CHECK-LABEL:   func.func @_QPissue80884(
+! CHECK:           %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFissue80884Ep"} : (!fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>) -> (!fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>, !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>)
+! CHECK:           %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}} {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QFissue80884Etarg"} : (!fir.ref<!fir.type<_QFissue80884Tt{t0:!fir.type<_QFissue80884Tt0{array:!fir.array<10x10xf32>}>}>>) -> (!fir.ref<!fir.type<_QFissue80884Tt{t0:!fir.type<_QFissue80884Tt0{array:!fir.array<10x10xf32>}>}>>, !fir.ref<!fir.type<_QFissue80884Tt{t0:!fir.type<_QFissue80884Tt0{array:!fir.array<10x10xf32>}>}>>)
+! CHECK:           %[[VAL_4:.*]] = arith.constant 1 : i64
+! CHECK:           %[[VAL_5:.*]] = arith.constant 100 : i64
+! CHECK:           %[[VAL_6:.*]] = hlfir.designate %[[VAL_3]]#0{"t0"}   : (!fir.ref<!fir.type<_QFissue80884Tt{t0:!fir.type<_QFissue80884Tt0{array:!fir.array<10x10xf32>}>}>>) -> !fir.ref<!fir.type<_QFissue80884Tt0{array:!fir.array<10x10xf32>}>>
+! CHECK:           %[[VAL_7:.*]] = arith.constant 10 : index
+! CHECK:           %[[VAL_8:.*]] = arith.constant 10 : index
+! CHECK:           %[[VAL_9:.*]] = fir.shape %[[VAL_7]], %[[VAL_8]] : (index, index) -> !fir.shape<2>
+! CHECK:           %[[VAL_10:.*]] = hlfir.designate %[[VAL_6]]{"array"}   shape %[[VAL_9]] : (!fir.ref<!fir.type<_QFissue80884Tt0{array:!fir.array<10x10xf32>}>>, !fir.shape<2>) -> !fir.ref<!fir.array<10x10xf32>>
+! CHECK:           %[[VAL_11:.*]] = arith.constant 1 : index
+! CHECK:           %[[VAL_12:.*]] = fir.convert %[[VAL_4]] : (i64) -> index
+! CHECK:           %[[VAL_13:.*]] = fir.convert %[[VAL_5]] : (i64) -> index
+! CHECK:           %[[VAL_14:.*]] = arith.subi %[[VAL_13]], %[[VAL_12]] : index
+! CHECK:           %[[VAL_15:.*]] = arith.addi %[[VAL_14]], %[[VAL_11]] : index
+! CHECK:           %[[VAL_16:.*]] = fir.convert %[[VAL_10]] : (!fir.ref<!fir.array<10x10xf32>>) -> !fir.ref<!fir.array<?xf32>>
+! CHECK:           %[[VAL_17:.*]] = fir.shape_shift %[[VAL_4]], %[[VAL_15]] : (i64, index) -> !fir.shapeshift<1>
+! CHECK:           %[[VAL_18:.*]] = fir.embox %[[VAL_16]](%[[VAL_17]]) : (!fir.ref<!fir.array<?xf32>>, !fir.shapeshift<1>) -> !fir.box<!fir.ptr<!fir.array<?xf32>>>
+! CHECK:           fir.store %[[VAL_18]] to %[[VAL_2]]#1 : !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>