diff --git a/flang/lib/Lower/Allocatable.cpp b/flang/lib/Lower/Allocatable.cpp
--- a/flang/lib/Lower/Allocatable.cpp
+++ b/flang/lib/Lower/Allocatable.cpp
@@ -41,11 +41,15 @@
     llvm::cl::desc("Lower allocations to fortran runtime calls"),
     llvm::cl::init(false));
 /// Switch to force lowering of allocatable and pointers to descriptors in all
-/// cases for debug purposes.
+/// cases. This is now turned on by default since that is what will happen with
+/// HLFIR lowering, so this allows getting early feedback of the impact.
+/// If this turns out to cause performance regressions, a dedicated fir.box
+/// "discretization pass" would make more sense to cover all the fir.box usage
+/// (taking advantage of any future inlining for instance).
 static llvm::cl::opt<bool> useDescForMutableBox(
     "use-desc-for-alloc",
     llvm::cl::desc("Always use descriptors for POINTER and ALLOCATABLE"),
-    llvm::cl::init(false));
+    llvm::cl::init(true));
 
 //===----------------------------------------------------------------------===//
 // Error management
diff --git a/flang/test/Lower/Intrinsics/c_loc.f90 b/flang/test/Lower/Intrinsics/c_loc.f90
--- a/flang/test/Lower/Intrinsics/c_loc.f90
+++ b/flang/test/Lower/Intrinsics/c_loc.f90
@@ -1,5 +1,5 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
-! RUN: %flang_fc1 -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false --emit-fir %s -o - | FileCheck %s
+! RUN: %flang_fc1 -mllvm --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! Test intrinsic module procedure c_loc
 
diff --git a/flang/test/Lower/Intrinsics/iall.f90 b/flang/test/Lower/Intrinsics/iall.f90
--- a/flang/test/Lower/Intrinsics/iall.f90
+++ b/flang/test/Lower/Intrinsics/iall.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: func @_QPiall_test_1(
 ! CHECK-SAME: %[[arg0:.*]]: !fir.box<!fir.array<?xi8>>{{.*}}) -> i8 {
diff --git a/flang/test/Lower/Intrinsics/iany.f90 b/flang/test/Lower/Intrinsics/iany.f90
--- a/flang/test/Lower/Intrinsics/iany.f90
+++ b/flang/test/Lower/Intrinsics/iany.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: func @_QPiany_test_1(
 ! CHECK-SAME: %[[arg0:.*]]: !fir.box<!fir.array<?xi8>>{{.*}}) -> i8 {
diff --git a/flang/test/Lower/Intrinsics/iparity.f90 b/flang/test/Lower/Intrinsics/iparity.f90
--- a/flang/test/Lower/Intrinsics/iparity.f90
+++ b/flang/test/Lower/Intrinsics/iparity.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: func @_QPiparity_test_1(
 ! CHECK-SAME: %[[arg0:.*]]: !fir.box<!fir.array<?xi8>>{{.*}}) -> i8 {
diff --git a/flang/test/Lower/Intrinsics/len.f90 b/flang/test/Lower/Intrinsics/len.f90
--- a/flang/test/Lower/Intrinsics/len.f90
+++ b/flang/test/Lower/Intrinsics/len.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: len_test
 subroutine len_test(i, c)
diff --git a/flang/test/Lower/Intrinsics/loc.f90 b/flang/test/Lower/Intrinsics/loc.f90
--- a/flang/test/Lower/Intrinsics/loc.f90
+++ b/flang/test/Lower/Intrinsics/loc.f90
@@ -1,5 +1,5 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
-! RUN: %flang_fc1 -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
+! RUN: %flang_fc1 -mllvm --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! Test LOC intrinsic
 
diff --git a/flang/test/Lower/Intrinsics/move_alloc.f90 b/flang/test/Lower/Intrinsics/move_alloc.f90
--- a/flang/test/Lower/Intrinsics/move_alloc.f90
+++ b/flang/test/Lower/Intrinsics/move_alloc.f90
@@ -1,5 +1,5 @@
-  ! RUN: bbc -emit-fir %s -o - | FileCheck  %s
-  ! RUN: flang-new -fc1 -emit-fir %s -o - | FileCheck %s
+  ! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck  %s
+  ! RUN: flang-new -fc1 -mllvm --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: to_from_only
 subroutine to_from_only
diff --git a/flang/test/Lower/Intrinsics/product.f90 b/flang/test/Lower/Intrinsics/product.f90
--- a/flang/test/Lower/Intrinsics/product.f90
+++ b/flang/test/Lower/Intrinsics/product.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: func @_QPproduct_test(
 ! CHECK-SAME: %[[arg0:.*]]: !fir.box<!fir.array<?xi32>>{{.*}}) -> i32
diff --git a/flang/test/Lower/Intrinsics/sum.f90 b/flang/test/Lower/Intrinsics/sum.f90
--- a/flang/test/Lower/Intrinsics/sum.f90
+++ b/flang/test/Lower/Intrinsics/sum.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: func @_QPsum_test(
 ! CHECK-SAME: %[[arg0:.*]]: !fir.box<!fir.array<?xi32>>{{.*}}) -> i32 {
diff --git a/flang/test/Lower/Intrinsics/system_clock.f90 b/flang/test/Lower/Intrinsics/system_clock.f90
--- a/flang/test/Lower/Intrinsics/system_clock.f90
+++ b/flang/test/Lower/Intrinsics/system_clock.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! CHECK-LABEL: system_clock_test
 subroutine system_clock_test()
diff --git a/flang/test/Lower/OpenACC/acc-data-operands.f90 b/flang/test/Lower/OpenACC/acc-data-operands.f90
--- a/flang/test/Lower/OpenACC/acc-data-operands.f90
+++ b/flang/test/Lower/OpenACC/acc-data-operands.f90
@@ -1,6 +1,6 @@
 ! This test checks lowering of complex OpenACC data operands.
 
-! RUN: bbc -fopenacc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -fopenacc -emit-fir %s -o - | FileCheck %s
 
 module acc_data_operand
 
diff --git a/flang/test/Lower/OpenMP/atomic-read.f90 b/flang/test/Lower/OpenMP/atomic-read.f90
--- a/flang/test/Lower/OpenMP/atomic-read.f90
+++ b/flang/test/Lower/OpenMP/atomic-read.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -fopenmp -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -fopenmp -emit-fir %s -o - | FileCheck %s
 
 ! This test checks the lowering of atomic read
 
diff --git a/flang/test/Lower/OpenMP/atomic-update.f90 b/flang/test/Lower/OpenMP/atomic-update.f90
--- a/flang/test/Lower/OpenMP/atomic-update.f90
+++ b/flang/test/Lower/OpenMP/atomic-update.f90
@@ -1,6 +1,6 @@
 ! This test checks lowering of atomic and atomic update constructs
-! RUN: bbc -fopenmp -emit-fir %s -o - | FileCheck %s
-! RUN: %flang_fc1 -emit-fir -fopenmp %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -fopenmp -emit-fir %s -o - | FileCheck %s
+! RUN: %flang_fc1 -mllvm --use-desc-for-alloc=false -emit-fir -fopenmp %s -o - | FileCheck %s
 
 program OmpAtomicUpdate
     use omp_lib
diff --git a/flang/test/Lower/OpenMP/atomic-write.f90 b/flang/test/Lower/OpenMP/atomic-write.f90
--- a/flang/test/Lower/OpenMP/atomic-write.f90
+++ b/flang/test/Lower/OpenMP/atomic-write.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -fopenmp -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -fopenmp -emit-fir %s -o - | FileCheck %s
 
 ! This test checks the lowering of atomic write
 
diff --git a/flang/test/Lower/OpenMP/parallel-private-clause.f90 b/flang/test/Lower/OpenMP/parallel-private-clause.f90
--- a/flang/test/Lower/OpenMP/parallel-private-clause.f90
+++ b/flang/test/Lower/OpenMP/parallel-private-clause.f90
@@ -2,7 +2,7 @@
 ! `PRIVATE` clause present.
 
 ! REQUIRES: shell
-! RUN: bbc -fopenmp -emit-fir %s -o - | \
+! RUN: bbc --use-desc-for-alloc=false -fopenmp -emit-fir %s -o - | \
 ! RUN:   FileCheck %s --check-prefix=FIRDialect
 
 !FIRDialect: func @_QPprivate_clause(%[[ARG1:.*]]: !fir.ref<i32>{{.*}}, %[[ARG2:.*]]: !fir.ref<!fir.array<10xi32>>{{.*}}, %[[ARG3:.*]]: !fir.boxchar<1>{{.*}}, %[[ARG4:.*]]: !fir.boxchar<1>{{.*}}) {
diff --git a/flang/test/Lower/allocatable-assignment.f90 b/flang/test/Lower/allocatable-assignment.f90
--- a/flang/test/Lower/allocatable-assignment.f90
+++ b/flang/test/Lower/allocatable-assignment.f90
@@ -1,5 +1,5 @@
 ! Test allocatable assignments
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 module alloc_assign
   type t
diff --git a/flang/test/Lower/allocatable-polymorphic.f90 b/flang/test/Lower/allocatable-polymorphic.f90
--- a/flang/test/Lower/allocatable-polymorphic.f90
+++ b/flang/test/Lower/allocatable-polymorphic.f90
@@ -1,5 +1,5 @@
-! RUN: bbc -polymorphic-type -emit-fir %s -o - | FileCheck %s
-! RUN: bbc -polymorphic-type -emit-fir %s -o - | tco | FileCheck %s --check-prefix=LLVM
+! RUN: bbc --use-desc-for-alloc=false -polymorphic-type -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -polymorphic-type -emit-fir %s -o - | tco | FileCheck %s --check-prefix=LLVM
 
 module poly
   type p1
diff --git a/flang/test/Lower/allocatables.f90 b/flang/test/Lower/allocatables.f90
--- a/flang/test/Lower/allocatables.f90
+++ b/flang/test/Lower/allocatables.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! Test lowering of allocatables using runtime for allocate/deallcoate statements.
 ! CHECK-LABEL: _QPfooscalar
diff --git a/flang/test/Lower/allocate-mold.f90 b/flang/test/Lower/allocate-mold.f90
--- a/flang/test/Lower/allocate-mold.f90
+++ b/flang/test/Lower/allocate-mold.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! Test lowering of ALLOCATE statement with a MOLD argument for scalars
 
diff --git a/flang/test/Lower/allocate-source-allocatables.f90 b/flang/test/Lower/allocate-source-allocatables.f90
--- a/flang/test/Lower/allocate-source-allocatables.f90
+++ b/flang/test/Lower/allocate-source-allocatables.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! Test lowering of allocatables for allocate statements with source.
 
diff --git a/flang/test/Lower/allocate-source-pointers.f90 b/flang/test/Lower/allocate-source-pointers.f90
--- a/flang/test/Lower/allocate-source-pointers.f90
+++ b/flang/test/Lower/allocate-source-pointers.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 ! Test lowering of pointers for allocate statements with source.
 
diff --git a/flang/test/Lower/array-constructor-2.f90 b/flang/test/Lower/array-constructor-2.f90
--- a/flang/test/Lower/array-constructor-2.f90
+++ b/flang/test/Lower/array-constructor-2.f90
@@ -1,4 +1,4 @@
-! RUN: bbc %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false %s -o - | FileCheck %s
 
 !  Constant array ctor.
 ! CHECK-LABEL: func @_QPtest1(
diff --git a/flang/test/Lower/character-assignment.f90 b/flang/test/Lower/character-assignment.f90
--- a/flang/test/Lower/character-assignment.f90
+++ b/flang/test/Lower/character-assignment.f90
@@ -1,4 +1,4 @@
-! RUN: bbc %s -o - -emit-fir | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false %s -o - -emit-fir | FileCheck %s
 
 ! Simple character assignment tests
 ! CHECK-LABEL: _QPassign1
diff --git a/flang/test/Lower/derived-type-finalization.f90 b/flang/test/Lower/derived-type-finalization.f90
--- a/flang/test/Lower/derived-type-finalization.f90
+++ b/flang/test/Lower/derived-type-finalization.f90
@@ -1,5 +1,5 @@
 ! Test derived type finalization
-! RUN: bbc -polymorphic-type -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -polymorphic-type -emit-fir %s -o - | FileCheck %s
 
 ! Missing tests:
 ! - finalization within BLOCK construct
diff --git a/flang/test/Lower/do_loop.f90 b/flang/test/Lower/do_loop.f90
--- a/flang/test/Lower/do_loop.f90
+++ b/flang/test/Lower/do_loop.f90
@@ -1,5 +1,5 @@
-! RUN: bbc -emit-fir -o - %s | FileCheck %s
-! RUN: %flang_fc1 -emit-fir -o - %s | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -mllvm --use-desc-for-alloc=false -emit-fir -o - %s | FileCheck %s
 
 ! Simple tests for structured ordered loops with loop-control.
 ! Tests the structure of the loop, storage to index variable and return and 
diff --git a/flang/test/Lower/forall/array-pointer.f90 b/flang/test/Lower/forall/array-pointer.f90
--- a/flang/test/Lower/forall/array-pointer.f90
+++ b/flang/test/Lower/forall/array-pointer.f90
@@ -6,7 +6,7 @@
 ! is a pointer to an array of T and never an array of pointer to T in
 ! Fortran.
 
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 module array_of_pointer_test
   type t
diff --git a/flang/test/Lower/forall/forall-allocatable.f90 b/flang/test/Lower/forall/forall-allocatable.f90
--- a/flang/test/Lower/forall/forall-allocatable.f90
+++ b/flang/test/Lower/forall/forall-allocatable.f90
@@ -1,6 +1,6 @@
 ! Test forall lowering
 
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 subroutine forall_with_allocatable(a1)
   real :: a1(:)
diff --git a/flang/test/Lower/intentout-deallocate.f90 b/flang/test/Lower/intentout-deallocate.f90
--- a/flang/test/Lower/intentout-deallocate.f90
+++ b/flang/test/Lower/intentout-deallocate.f90
@@ -1,5 +1,5 @@
 ! Test correct deallocation of intent(out) allocatables.
-! RUN: bbc -emit-fir -polymorphic-type %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir -polymorphic-type %s -o - | FileCheck %s
 
 module mod1
   type, bind(c) :: t1
diff --git a/flang/test/Lower/io-implied-do-fixes.f90 b/flang/test/Lower/io-implied-do-fixes.f90
--- a/flang/test/Lower/io-implied-do-fixes.f90
+++ b/flang/test/Lower/io-implied-do-fixes.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 ! UNSUPPORTED: system-windows
 
 ! CHECK-LABEL: func @_QPido1
diff --git a/flang/test/Lower/parent-component.f90 b/flang/test/Lower/parent-component.f90
--- a/flang/test/Lower/parent-component.f90
+++ b/flang/test/Lower/parent-component.f90
@@ -1,7 +1,7 @@
 ! Test different ways of passing the parent component of an extended
 ! derived-type to a subroutine or the runtime.
 
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 program parent_comp
   type p
diff --git a/flang/test/Lower/pointer-assignments.f90 b/flang/test/Lower/pointer-assignments.f90
--- a/flang/test/Lower/pointer-assignments.f90
+++ b/flang/test/Lower/pointer-assignments.f90
@@ -1,5 +1,5 @@
 ! Test lowering of pointer assignments
-! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -emit-fir %s -o - | FileCheck %s
 
 
 ! Note that p => NULL() are tested in pointer-disassociate.f90
diff --git a/flang/test/Lower/polymorphic.f90 b/flang/test/Lower/polymorphic.f90
--- a/flang/test/Lower/polymorphic.f90
+++ b/flang/test/Lower/polymorphic.f90
@@ -1,4 +1,4 @@
-! RUN: bbc -polymorphic-type -emit-fir %s -o - | FileCheck %s
+! RUN: bbc --use-desc-for-alloc=false -polymorphic-type -emit-fir %s -o - | FileCheck %s
 
 ! Tests various aspect of the lowering of polymorphic entities.