On Tue, 8 Nov 2022, Qing Zhao wrote:
> The name of the utility routine "array_at_struct_end_p" is misleading
> and should be changed to a new name that more accurately reflects its
> real meaning.
>
> The routine "array_at_struct_end_p" is used to check whether an array
> reference is to an array whose actual size might be larger than its
> upper bound implies, which includes 3 different cases:
>
> A. a ref to a flexible array member at the end of a structure;
> B. a ref to an array with a different type against the original decl;
> C. a ref to an array that was passed as a parameter;
>
> The old name only reflects the above case A, therefore very confusing
> when reading the corresponding gcc source code.
>
> In this patch, A new name "array_ref_flexible_size_p" is used to replace
> the old name.
>
> All the references to the routine "array_at_struct_end_p" was replaced
> with this new name, and the corresponding comments were updated to make
> them clean and consistent.
Since you seem to feel strongly about this - OK.
Thanks,
Richard.
> gcc/ChangeLog:
>
> * gimple-array-bounds.cc (trailing_array): Replace
> array_at_struct_end_p with new name and update comments.
> * gimple-fold.cc (get_range_strlen_tree): Likewise.
> * gimple-ssa-warn-restrict.cc (builtin_memref::builtin_memref):
> Likewise.
> * graphite-sese-to-poly.cc (bounds_are_valid): Likewise.
> * tree-if-conv.cc (idx_within_array_bound): Likewise.
> * tree-object-size.cc (addr_object_size): Likewise.
> * tree-ssa-alias.cc (component_ref_to_zero_sized_trailing_array_p):
> Likewise.
> (stmt_kills_ref_p): Likewise.
> * tree-ssa-loop-niter.cc (idx_infer_loop_bounds): Likewise.
> * tree-ssa-strlen.cc (maybe_set_strlen_range): Likewise.
> * tree.cc (array_at_struct_end_p): Rename to ...
> (array_ref_flexible_size_p): ... this.
> (component_ref_size): Replace array_at_struct_end_p with new name.
> * tree.h (array_at_struct_end_p): Rename to ...
> (array_ref_flexible_size_p): ... this.
> ---
> gcc/gimple-array-bounds.cc | 4 ++--
> gcc/gimple-fold.cc | 6 ++----
> gcc/gimple-ssa-warn-restrict.cc | 5 +++--
> gcc/graphite-sese-to-poly.cc | 4 ++--
> gcc/tree-if-conv.cc | 7 +++----
> gcc/tree-object-size.cc | 2 +-
> gcc/tree-ssa-alias.cc | 8 ++++----
> gcc/tree-ssa-loop-niter.cc | 15 +++++++--------
> gcc/tree-ssa-strlen.cc | 2 +-
> gcc/tree.cc | 11 ++++++-----
> gcc/tree.h | 8 ++++----
> 11 files changed, 35 insertions(+), 37 deletions(-)
>
> diff --git a/gcc/gimple-array-bounds.cc b/gcc/gimple-array-bounds.cc
> index e190b93aa85..fbf448e045d 100644
> --- a/gcc/gimple-array-bounds.cc
> +++ b/gcc/gimple-array-bounds.cc
> @@ -129,7 +129,7 @@ get_ref_size (tree arg, tree *pref)
> }
>
> /* Return true if REF is (likely) an ARRAY_REF to a trailing array member
> - of a struct. It refines array_at_struct_end_p by detecting a pointer
> + of a struct. It refines array_ref_flexible_size_p by detecting a pointer
> to an array and an array parameter declared using the [N] syntax (as
> opposed to a pointer) and returning false. Set *PREF to the decl or
> expression REF refers to. */
> @@ -167,7 +167,7 @@ trailing_array (tree arg, tree *pref)
> return false;
> }
>
> - return array_at_struct_end_p (arg);
> + return array_ref_flexible_size_p (arg);
> }
>
> /* Checks one ARRAY_REF in REF, located at LOCUS. Ignores flexible
> diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
> index 9055cd8982d..cafd331ca98 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -1690,13 +1690,11 @@ get_range_strlen_tree (tree arg, bitmap visited,
> strlen_range_kind rkind,
> /* Handle a MEM_REF into a DECL accessing an array of integers,
> being conservative about references to extern structures with
> flexible array members that can be initialized to arbitrary
> - numbers of elements as an extension (static structs are okay).
> - FIXME: Make this less conservative -- see
> - component_ref_size in tree.cc. */
> + numbers of elements as an extension (static structs are okay). */
> tree ref = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
> if ((TREE_CODE (ref) == PARM_DECL || VAR_P (ref))
> && (decl_binds_to_current_def_p (ref)
> - || !array_at_struct_end_p (arg)))
> + || !array_ref_flexible_size_p (arg)))
> {
> /* Fail if the offset is out of bounds. Such accesses
> should be diagnosed at some point. */
> diff --git a/gcc/gimple-ssa-warn-restrict.cc b/gcc/gimple-ssa-warn-restrict.cc
> index b7ed15c8902..832456ba6fc 100644
> --- a/gcc/gimple-ssa-warn-restrict.cc
> +++ b/gcc/gimple-ssa-warn-restrict.cc
> @@ -296,8 +296,9 @@ builtin_memref::builtin_memref (pointer_query &ptrqry,
> gimple *stmt, tree expr,
> tree basetype = TREE_TYPE (base);
> if (TREE_CODE (basetype) == ARRAY_TYPE)
> {
> - if (ref && array_at_struct_end_p (ref))
> - ; /* Use the maximum possible offset for last member arrays. */
> + if (ref && array_ref_flexible_size_p (ref))
> + ; /* Use the maximum possible offset for an array that might
> + have flexible size. */
> else if (tree basesize = TYPE_SIZE_UNIT (basetype))
> if (TREE_CODE (basesize) == INTEGER_CST)
> /* Size could be non-constant for a variable-length type such
> diff --git a/gcc/graphite-sese-to-poly.cc b/gcc/graphite-sese-to-poly.cc
> index 51ba3af204f..7eb24c1c991 100644
> --- a/gcc/graphite-sese-to-poly.cc
> +++ b/gcc/graphite-sese-to-poly.cc
> @@ -536,9 +536,9 @@ bounds_are_valid (tree ref, tree low, tree high)
> || !tree_fits_shwi_p (high))
> return false;
>
> - /* 1-element arrays at end of structures may extend over
> + /* An array that has flexible size may extend over
> their declared size. */
> - if (array_at_struct_end_p (ref)
> + if (array_ref_flexible_size_p (ref)
> && operand_equal_p (low, high, 0))
> return false;
>
> diff --git a/gcc/tree-if-conv.cc b/gcc/tree-if-conv.cc
> index a83b013d2ad..34bb507ff3b 100644
> --- a/gcc/tree-if-conv.cc
> +++ b/gcc/tree-if-conv.cc
> @@ -763,10 +763,9 @@ idx_within_array_bound (tree ref, tree *idx, void *dta)
> if (TREE_CODE (ref) != ARRAY_REF)
> return false;
>
> - /* For arrays at the end of the structure, we are not guaranteed that they
> - do not really extend over their declared size. However, for arrays of
> - size greater than one, this is unlikely to be intended. */
> - if (array_at_struct_end_p (ref))
> + /* For arrays that might have flexible sizes, it is not guaranteed that
> they
> + do not extend over their declared size. */
> + if (array_ref_flexible_size_p (ref))
> return false;
>
> ev = analyze_scalar_evolution (loop, *idx);
> diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc
> index 1f04cb80fd0..2e5d267d8ce 100644
> --- a/gcc/tree-object-size.cc
> +++ b/gcc/tree-object-size.cc
> @@ -633,7 +633,7 @@ addr_object_size (struct object_size_info *osi,
> const_tree ptr,
> v = NULL_TREE;
> break;
> }
> - is_flexible_array_mem_ref = array_at_struct_end_p (v);
> + is_flexible_array_mem_ref = array_ref_flexible_size_p (v);
> while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
> if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
> != UNION_TYPE
> diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
> index b4c65da5718..d3a91b1f238 100644
> --- a/gcc/tree-ssa-alias.cc
> +++ b/gcc/tree-ssa-alias.cc
> @@ -1073,7 +1073,7 @@ component_ref_to_zero_sized_trailing_array_p (tree ref)
> && TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 1))) == ARRAY_TYPE
> && (!TYPE_SIZE (TREE_TYPE (TREE_OPERAND (ref, 1)))
> || integer_zerop (TYPE_SIZE (TREE_TYPE (TREE_OPERAND (ref, 1)))))
> - && array_at_struct_end_p (ref));
> + && array_ref_flexible_size_p (ref));
> }
>
> /* Worker for aliasing_component_refs_p. Most parameters match parameters of
> @@ -3433,10 +3433,10 @@ stmt_kills_ref_p (gimple *stmt, ao_ref *ref)
> }
> /* Finally check if the lhs has the same address and size as the
> base candidate of the access. Watch out if we have dropped
> - an array-ref that was at struct end, this means ref->ref may
> - be outside of the TYPE_SIZE of its base. */
> + an array-ref that might have flexible size, this means ref->ref
> + may be outside of the TYPE_SIZE of its base. */
> if ((! innermost_dropped_array_ref
> - || ! array_at_struct_end_p (innermost_dropped_array_ref))
> + || ! array_ref_flexible_size_p (innermost_dropped_array_ref))
> && (lhs == base
> || (((TYPE_SIZE (TREE_TYPE (lhs))
> == TYPE_SIZE (TREE_TYPE (base)))
> diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc
> index 4ffcef4f4ff..3fbbf4367ed 100644
> --- a/gcc/tree-ssa-loop-niter.cc
> +++ b/gcc/tree-ssa-loop-niter.cc
> @@ -3716,18 +3716,17 @@ idx_infer_loop_bounds (tree base, tree *idx, void
> *dta)
> struct ilb_data *data = (struct ilb_data *) dta;
> tree ev, init, step;
> tree low, high, type, next;
> - bool sign, upper = true, at_end = false;
> + bool sign, upper = true, has_flexible_size = false;
> class loop *loop = data->loop;
>
> if (TREE_CODE (base) != ARRAY_REF)
> return true;
>
> - /* For arrays at the end of the structure, we are not guaranteed that they
> - do not really extend over their declared size. However, for arrays of
> - size greater than one, this is unlikely to be intended. */
> - if (array_at_struct_end_p (base))
> + /* For arrays that might have flexible sizes, it is not guaranteed that
> they
> + do not really extend over their declared size. */
> + if (array_ref_flexible_size_p (base))
> {
> - at_end = true;
> + has_flexible_size = true;
> upper = false;
> }
>
> @@ -3760,9 +3759,9 @@ idx_infer_loop_bounds (tree base, tree *idx, void *dta)
> sign = tree_int_cst_sign_bit (step);
> type = TREE_TYPE (step);
>
> - /* The array of length 1 at the end of a structure most likely extends
> + /* The array that might have flexible size most likely extends
> beyond its bounds. */
> - if (at_end
> + if (has_flexible_size
> && operand_equal_p (low, high, 0))
> return true;
>
> diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
> index 5afbae1b72e..b87c7c7ce1f 100644
> --- a/gcc/tree-ssa-strlen.cc
> +++ b/gcc/tree-ssa-strlen.cc
> @@ -1987,7 +1987,7 @@ maybe_set_strlen_range (tree lhs, tree src, tree bound)
> suggests if it's treated as a poor-man's flexible array member. */
> src = TREE_OPERAND (src, 0);
> if (TREE_CODE (src) != MEM_REF
> - && !array_at_struct_end_p (src))
> + && !array_ref_flexible_size_p (src))
> {
> tree type = TREE_TYPE (src);
> tree size = TYPE_SIZE_UNIT (type);
> diff --git a/gcc/tree.cc b/gcc/tree.cc
> index 04603c8c902..d2b0b34a725 100644
> --- a/gcc/tree.cc
> +++ b/gcc/tree.cc
> @@ -12710,8 +12710,8 @@ array_ref_up_bound (tree exp)
> return NULL_TREE;
> }
>
> -/* Returns true if REF is an array reference, component reference,
> - or memory reference to an array whose actual size might be larger
> +/* Returns true if REF is an array reference, a component reference,
> + or a memory reference to an array whose actual size might be larger
> than its upper bound implies, there are multiple cases:
> A. a ref to a flexible array member at the end of a structure;
> B. a ref to an array with a different type against the original decl;
> @@ -12726,10 +12726,10 @@ array_ref_up_bound (tree exp)
> int test (uint8_t *p, uint32_t t[1][1], int n) {
> for (int i = 0; i < 4; i++, p++)
> t[i][0] = ...;
> +*/
>
> - FIXME, the name of this routine need to be changed to be more accurate.
> */
> bool
> -array_at_struct_end_p (tree ref)
> +array_ref_flexible_size_p (tree ref)
> {
> /* the TYPE for this array referece. */
> tree atype = NULL_TREE;
> @@ -12862,6 +12862,7 @@ array_at_struct_end_p (tree ref)
> return afield_decl ? !DECL_NOT_FLEXARRAY (afield_decl) : true;
> }
>
> +
> /* Return a tree representing the offset, in bytes, of the field referenced
> by EXP. This does not include any offset in DECL_FIELD_BIT_OFFSET. */
>
> @@ -12957,7 +12958,7 @@ component_ref_size (tree ref, special_array_member
> *sam /* = NULL */)
> return (tree_int_cst_equal (memsize, TYPE_SIZE_UNIT (memtype))
> ? memsize : NULL_TREE);
>
> - bool trailing = array_at_struct_end_p (ref);
> + bool trailing = array_ref_flexible_size_p (ref);
> bool zero_length = integer_zerop (memsize);
> if (!trailing && !zero_length)
> /* MEMBER is either an interior array or is an array with
> diff --git a/gcc/tree.h b/gcc/tree.h
> index a50f7b2be9d..0fcdd6b06d0 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -5548,10 +5548,10 @@ extern tree array_ref_up_bound (tree);
> EXP, an ARRAY_REF or an ARRAY_RANGE_REF. */
> extern tree array_ref_low_bound (tree);
>
> -/* Returns true if REF is an array reference or a component reference
> - to an array at the end of a structure. If this is the case, the array
> - may be allocated larger than its upper bound implies. */
> -extern bool array_at_struct_end_p (tree);
> +/* Returns true if REF is an array reference, a component reference,
> + or a memory reference to an array whose actual size might be larger
> + than its upper bound implies. */
> +extern bool array_ref_flexible_size_p (tree);
>
> /* Return a tree representing the offset, in bytes, of the field referenced
> by EXP. This does not include any offset in DECL_FIELD_BIT_OFFSET. */
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
