Re: [PATCH] Fix up Fortran debug info for arrays with descriptors (PR fortran/92775)

[Tobias Burnus]

@Paul: I have an ISO-C question for you.

On 12/6/19 1:16 AM, Jakub Jelinek wrote:
[…]
Unfortunately, I don't know Fortran enough to find out when exactly the
compiler knows that descr->span will be always equal to element_size,

Well, while gfc_expr is still available, that's gfc_get_array_span; if 
it is neither a pointer (in the Fortran sense)/ISO-C descriptor nor a 
polymorphic, it has the element length [for strings: times the string 
length].

Instead of going for the general solution, I wonder whether one could 
use something like: If type is integer/real/complex and not a pointer, 
take the element size; namely, something like:

if (GFC_TYPE_ARRAY_AKIND (type) != GFC_ARRAY_POINTER
    && (INTEGRAL_TYPE_P (type) || SCALAR_FLOAT_TYPE_P (type)
        || COMPLEX_FLOAT_TYPE_P (type)))

That wouldn't cover known-size/nonpolymorphic derived types nor compile-time
const strings (span = <unit size of char type> * <string length>) but at least
the ubiquitous numeric arrays.
It surely could be refined to cover the rest (fixed-length strings, 
nonpolymorphic
types).

I only don't quickly see which GFC_TYPE_ARRAY_AKIND the ISO-C descriptor
gets, i.e. whether condition above will work or whether something in addition
is needed.

Paul?

(For me the whole gfc <-> ISO C descriptor handling looks like a mess,
but I also have not yet tried to fully understood how it works in detail.)
 

In the meantime, I think it is better to go for correct debug info over
saving the 3 bytes in .debug_info per dimension.

The patch also removes fields/macros that aren't ever used since r251949
and just waste compile time memory.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK; thanks for the patch!

Tobias

2019-12-06  Jakub Jelinek  <ja...@redhat.com>

        PR fortran/92775
        * trans.h (struct lang_type, struct lang_decl): Remove span member.
        (GFC_DECL_SPAN, GFC_TYPE_ARRAY_SPAN): Remove macros.
        * trans-array.h (gfc_get_descriptor_offsets_for_info): Add another
        argument.
        * trans-array.c (gfc_get_descriptor_offsets_for_info): Add SPAN_OFF
        argument and initialize *SPAN_OFF to the offset of span field.
        * trans-types.c (gfc_get_array_descr_info): Adjust
        gfc_get_descriptor_offsets_for_info caller.  Compute elem_size
        as base->span instead of TYPE_SIZE_UNIT (etype) constant.

--- gcc/fortran/trans.h.jj      2019-11-11 21:04:05.210259346 +0100
+++ gcc/fortran/trans.h 2019-12-05 11:23:55.935237355 +0100
@@ -981,7 +981,6 @@ struct GTY(())      lang_type        {
    tree offset;
    tree dtype;
    tree dataptr_type;
-  tree span;
    tree base_decl[2];
    tree nonrestricted_type;
    tree caf_token;
@@ -997,7 +996,6 @@ struct GTY(()) lang_decl {
       address of target label.  */
    tree stringlen;
    tree addr;
-  tree span;
    /* For assumed-shape coarrays.  */
    tree token, caf_offset;
    unsigned int scalar_allocatable : 1;
@@ -1008,7 +1006,6 @@ struct GTY(()) lang_decl {
  
  #define GFC_DECL_ASSIGN_ADDR(node) DECL_LANG_SPECIFIC(node)->addr
  #define GFC_DECL_STRING_LEN(node) DECL_LANG_SPECIFIC(node)->stringlen
-#define GFC_DECL_SPAN(node) DECL_LANG_SPECIFIC(node)->span
  #define GFC_DECL_TOKEN(node) DECL_LANG_SPECIFIC(node)->token
  #define GFC_DECL_CAF_OFFSET(node) DECL_LANG_SPECIFIC(node)->caf_offset
  #define GFC_DECL_SAVED_DESCRIPTOR(node) \
@@ -1059,7 +1056,6 @@ struct GTY(()) lang_decl {
  #define GFC_TYPE_ARRAY_DTYPE(node) (TYPE_LANG_SPECIFIC(node)->dtype)
  #define GFC_TYPE_ARRAY_DATAPTR_TYPE(node) \
    (TYPE_LANG_SPECIFIC(node)->dataptr_type)
-#define GFC_TYPE_ARRAY_SPAN(node) (TYPE_LANG_SPECIFIC(node)->span)
  #define GFC_TYPE_ARRAY_BASE_DECL(node, internal) \
    (TYPE_LANG_SPECIFIC(node)->base_decl[(internal)])
  
--- gcc/fortran/trans-array.h.jj	2019-09-26 22:02:40.236457478 +0200
+++ gcc/fortran/trans-array.h   2019-12-05 11:07:52.255125510 +0100
@@ -163,7 +163,7 @@ void gfc_trans_array_cobounds (tree, stm
  
  /* Build expressions for accessing components of an array descriptor.  */
  void gfc_get_descriptor_offsets_for_info (const_tree, tree *, tree *, tree *, 
tree *,
-                                         tree *, tree *, tree *);
+                                         tree *, tree *, tree *, tree *);
  
  tree gfc_conv_descriptor_data_get (tree);
  tree gfc_conv_descriptor_data_addr (tree);
--- gcc/fortran/trans-array.c.jj        2019-11-01 09:01:50.111998535 +0100
+++ gcc/fortran/trans-array.c   2019-12-05 11:09:38.545483494 +0100
@@ -540,9 +540,10 @@ gfc_conv_shift_descriptor_lbound (stmtbl
  
  void
  gfc_get_descriptor_offsets_for_info (const_tree desc_type, tree *data_off,
-                                    tree *dtype_off, tree *dim_off,
-                                    tree *dim_size, tree *stride_suboff,
-                                    tree *lower_suboff, tree *upper_suboff)
+                                    tree *dtype_off, tree *span_off,
+                                    tree *dim_off, tree *dim_size,
+                                    tree *stride_suboff, tree *lower_suboff,
+                                    tree *upper_suboff)
  {
    tree field;
    tree type;
@@ -552,6 +553,8 @@ gfc_get_descriptor_offsets_for_info (con
    *data_off = byte_position (field);
    field = gfc_advance_chain (TYPE_FIELDS (type), DTYPE_FIELD);
    *dtype_off = byte_position (field);
+  field = gfc_advance_chain (TYPE_FIELDS (type), SPAN_FIELD);
+  *span_off = byte_position (field);
    field = gfc_advance_chain (TYPE_FIELDS (type), DIMENSION_FIELD);
    *dim_off = byte_position (field);
    type = TREE_TYPE (TREE_TYPE (field));
--- gcc/fortran/trans-types.c.jj        2019-08-27 12:27:05.678497543 +0200
+++ gcc/fortran/trans-types.c   2019-12-05 11:39:33.868747876 +0100
@@ -3266,7 +3266,7 @@ gfc_get_array_descr_info (const_tree typ
    int rank, dim;
    bool indirect = false;
    tree etype, ptype, t, base_decl;
-  tree data_off, dim_off, dtype_off, dim_size, elem_size;
+  tree data_off, span_off, dim_off, dtype_off, dim_size, elem_size;
    tree lower_suboff, upper_suboff, stride_suboff;
    tree dtype, field, rank_off;
  
@@ -3323,12 +3323,13 @@ gfc_get_array_descr_info (const_tree typ
    if (indirect)
      base_decl = build1 (INDIRECT_REF, ptype, base_decl);
  
-  elem_size = fold_convert (gfc_array_index_type, TYPE_SIZE_UNIT (etype));
-
-  gfc_get_descriptor_offsets_for_info (type, &data_off, &dtype_off, &dim_off,
-                                      &dim_size, &stride_suboff,
+  gfc_get_descriptor_offsets_for_info (type, &data_off, &dtype_off, &span_off,
+                                      &dim_off, &dim_size, &stride_suboff,
                                       &lower_suboff, &upper_suboff);
  
+  t = fold_build_pointer_plus (base_decl, span_off);
+  elem_size = build1 (INDIRECT_REF, gfc_array_index_type, t);
+
    t = base_decl;
    if (!integer_zerop (data_off))
      t = fold_build_pointer_plus (t, data_off);