Thanks.
Committed as: https://gcc.gnu.org/pipermail/gcc-cvs/2022-November/373830.html
Qing
> On Nov 9, 2022, at 2:57 AM, Richard Biener <rguent...@suse.de> wrote:
>
> 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)
