Hi,
This is the 8th version of the patch.
compare with the 7th version, the difference are:
updates per Joseph's comments:
1. Wording changes in diagnostics;
"non flexible" to "non-flexible";
Diagnostics starts with a lowercase letter;
2. Documentation changes:
"named ``@var{count}'' to ``@var{count}'';
use present tense in the documentation;
3. Checking "INTEGRAL_TYPE_P" instead of just INTEGER_TYPE for integer types.
Add testcases for _Bool/enum/_BitInt count fields.
4. Add handling for multiple counted_by attributes on the same field:
Allow duplicates if they name the same field;
Error when they name different fields.
Add testcase for this.
5. Updates for comments style.
The 7th version is at:
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/648087.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/648088.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/648089.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/648090.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-March/648091.html
It based on the following original proposal:
https://gcc.gnu.org/pipermail/gcc-patches/2023-November/635884.html
Represent the missing dependence for the "counted_by" attribute and its
consumers
**The summary of the proposal is:
* Add a new internal function ".ACCESS_WITH_SIZE" to carry the size information
for every reference to a FAM field;
* In C FE, Replace every reference to a FAM field whose TYPE has the
"counted_by" attribute with the new internal function ".ACCESS_WITH_SIZE";
* In every consumer of the size information, for example, BDOS or array bound
sanitizer, query the size information or ACCESS_MODE information from the new
internal function;
* When expansing to RTL, replace the internal function with the actual
reference to the FAM field;
* Some adjustment to ipa alias analysis, and other SSA passes to mitigate the
impact to the optimizer and code generation.
**The new internal function
.ACCESS_WITH_SIZE (REF_TO_OBJ, REF_TO_SIZE, CLASS_OF_SIZE, TYPE_OF_SIZE,
ACCESS_MODE, TYPE_OF_REF)
INTERNAL_FN (ACCESS_WITH_SIZE, ECF_LEAF | ECF_NOTHROW, NULL)
which returns the "REF_TO_OBJ" same as the 1st argument;
Both the return type and the type of the first argument of this function have
been converted from the incomplete array type to the corresponding pointer type.
The call to .ACCESS_WITH_SIZE is wrapped with an INDIRECT_REF, whose type is
the original imcomplete array type.
Please see the following link for why:
https://gcc.gnu.org/pipermail/gcc-patches/2023-November/638793.html
https://gcc.gnu.org/pipermail/gcc-patches/2023-December/639605.html
1st argument "REF_TO_OBJ": The reference to the object;
2nd argument "REF_TO_SIZE": The reference to the size of the object,
3rd argument "CLASS_OF_SIZE": The size referenced by the REF_TO_SIZE represents
0: the number of bytes;
1: the number of the elements of the object type;
4th argument "TYPE_OF_SIZE": A constant 0 with the TYPE of the object
refed by REF_TO_SIZE
5th argument "ACCESS_MODE":
-1: Unknown access semantics
0: none
1: read_only
2: write_only
3: read_write
6th argument "TYPE_OF_REF": A constant 0 with the pointer TYPE to
to the original flexible array type.
** The Patch sets included:
1. Provide counted_by attribute to flexible array member field;
which includes:
* "counted_by" attribute documentation;
* C FE handling of the new attribute;
syntax checking, error reporting;
* testing cases;
2. Convert "counted_by" attribute to/from .ACCESS_WITH_SIZE.
which includes:
* The definition of the new internal function .ACCESS_WITH_SIZE in
internal-fn.def.
* C FE converts every reference to a FAM with "counted_by" attribute to a
call to the internal function .ACCESS_WITH_SIZE.
(build_component_ref in c_typeck.cc)
This includes the case when the object is statically allocated and
initialized.
In order to make this working, we should update
initializer_constant_valid_p_1 and output_constant in varasm.cc to include
calls to .ACCESS_WITH_SIZE.
However, for the reference inside "offsetof", ignore the "counted_by"
attribute since it's not useful at all. (c_parser_postfix_expression in
c/c-parser.cc)
In addtion to "offsetof", for the reference inside operator "typeof" and
"alignof", we ignore counted_by attribute too.
When building ADDR_EXPR for the .ACCESS_WITH_SIZE in C FE,
replace the call with its first argument.
* Convert every call to .ACCESS_WITH_SIZE to its first argument.
(expand_ACCESS_WITH_SIZE in internal-fn.cc)
* adjust alias analysis to exclude the new internal from clobbering
anything.
(ref_maybe_used_by_call_p_1 and call_may_clobber_ref_p_1 in
tree-ssa-alias.cc)
* adjust dead code elimination to eliminate the call to .ACCESS_WITH_SIZE
when
it's LHS is eliminated as dead code.
(el
