Re: [PATCH v2 4/8] gimple: Handle variable-sized vectors in BIT_FIELD_REF

[Tejas Belagod]

On 11/18/24 6:58 PM, Richard Sandiford wrote:
Tejas Belagod <tejas.bela...@arm.com> writes:
Handle variable-sized vectors for BIT_FIELD_REF canonicalization.
gcc/ChangeLog:

        * gimple-fold.cc (maybe_canonicalize_mem_ref_addr): Handle variable
        sized vector types in BIT_FIELD_REF canonicalization.
        * tree-cfg.cc (verify_types_in_gimple_reference): Change object-size-
        checking for BIT_FIELD_REF to error offsets that are known_gt to be
        outside object-size.  Out-of-range offsets can happen in the case of
        indices that reference VLA SVE vector elements that may be outside the
        minimum vector size range and therefore maybe_gt is not appropirate
        here.
---
  gcc/gimple-fold.cc | 3 ++-
  gcc/tree-cfg.cc    | 2 +-
  2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index c19dac0dbfd..97ac6f5379f 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -6294,7 +6294,8 @@ maybe_canonicalize_mem_ref_addr (tree *t, bool is_debug = 
false)
                                         (TYPE_SIZE (TREE_TYPE (*t))));
                  widest_int ext
                    = wi::add (idx, wi::to_widest (TYPE_SIZE (TREE_TYPE (*t))));
-                 if (wi::les_p (ext, wi::to_widest (TYPE_SIZE (vtype))))
+                 if (known_le (ext, wi::to_poly_widest (TYPE_SIZE (vtype)))
+                     || !wi::to_poly_widest (TYPE_SIZE (vtype)).is_constant ())

Did you consider using:

                  if (maybe_le (ext, wi::to_poly_widest (TYPE_SIZE (vtype))))

here, without the is_constant definition?  That seems to match the
tree-cfg.cc code more closely.

Ah, that's more apt here. I hadn't considered that - my brain is still 
wired to think VLS and VLA is terms of known_* and is_constant (). 
Thanks for this suggestion - I'll fix it.

Thanks,
Tejas.



Thanks,
Richard


                    {
                      *t = build3_loc (EXPR_LOCATION (*t), BIT_FIELD_REF,
                                       TREE_TYPE (*t),
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 3eede0d61cd..5a44b89907e 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -3176,7 +3176,7 @@ verify_types_in_gimple_reference (tree expr, bool 
require_lvalue)
              return true;
            }
          if (!AGGREGATE_TYPE_P (TREE_TYPE (op))
-             && maybe_gt (size + bitpos,
+             && known_gt (size + bitpos,
                           tree_to_poly_uint64 (TYPE_SIZE (TREE_TYPE (op)))))
            {
              error ("position plus size exceeds size of referenced object in "