[PATCH] Fix host_size_t_cst_p predicate

Richard Biener richard.guenther@gmail.com
Mon Oct 31 09:38:00 GMT 2016


On Mon, Oct 31, 2016 at 10:10 AM, Martin Liška <mliska@suse.cz> wrote:
> On 10/31/2016 01:12 AM, Richard Sandiford wrote:
>> Richard Biener <richard.guenther@gmail.com> writes:
>>> On Thu, Oct 27, 2016 at 5:06 PM, Martin Liška <mliska@suse.cz> wrote:
>>>> On 10/27/2016 03:35 PM, Richard Biener wrote:
>>>>> On Thu, Oct 27, 2016 at 9:41 AM, Martin Liška <mliska@suse.cz> wrote:
>>>>>> Running simple test-case w/o the proper header file causes ICE:
>>>>>> strncmp ("a", "b", -1);
>>>>>>
>>>>>> 0xe74462 tree_to_uhwi(tree_node const*)
>>>>>>         ../../gcc/tree.c:7324
>>>>>> 0x90a23f host_size_t_cst_p
>>>>>>         ../../gcc/fold-const-call.c:63
>>>>>> 0x90a23f fold_const_call(combined_fn, tree_node*, tree_node*,
>>>>>> tree_node*, tree_node*)
>>>>>>         ../../gcc/fold-const-call.c:1512
>>>>>> 0x787b01 fold_builtin_3
>>>>>>         ../../gcc/builtins.c:8385
>>>>>> 0x787b01 fold_builtin_n(unsigned int, tree_node*, tree_node**, int, bool)
>>>>>>         ../../gcc/builtins.c:8465
>>>>>> 0x9052b1 fold(tree_node*)
>>>>>>         ../../gcc/fold-const.c:11919
>>>>>> 0x6de2bb c_fully_fold_internal
>>>>>>         ../../gcc/c/c-fold.c:185
>>>>>> 0x6e1f6b c_fully_fold(tree_node*, bool, bool*)
>>>>>>         ../../gcc/c/c-fold.c:90
>>>>>> 0x67cbbf c_process_expr_stmt(unsigned int, tree_node*)
>>>>>>         ../../gcc/c/c-typeck.c:10369
>>>>>> 0x67cfbd c_finish_expr_stmt(unsigned int, tree_node*)
>>>>>>         ../../gcc/c/c-typeck.c:10414
>>>>>> 0x6cb578 c_parser_statement_after_labels
>>>>>>         ../../gcc/c/c-parser.c:5430
>>>>>> 0x6cd333 c_parser_compound_statement_nostart
>>>>>>         ../../gcc/c/c-parser.c:4944
>>>>>> 0x6cdbde c_parser_compound_statement
>>>>>>         ../../gcc/c/c-parser.c:4777
>>>>>> 0x6c93ac c_parser_declaration_or_fndef
>>>>>>         ../../gcc/c/c-parser.c:2176
>>>>>> 0x6d51ab c_parser_external_declaration
>>>>>>         ../../gcc/c/c-parser.c:1574
>>>>>> 0x6d5c09 c_parser_translation_unit
>>>>>>         ../../gcc/c/c-parser.c:1454
>>>>>> 0x6d5c09 c_parse_file()
>>>>>>         ../../gcc/c/c-parser.c:18173
>>>>>> 0x72ffd2 c_common_parse_file()
>>>>>>         ../../gcc/c-family/c-opts.c:1087
>>>>>>
>>>>>> Following patch improves the host_size_t_cst_p predicate.
>>>>>>
>>>>>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>>>>>>
>>>>>> Ready to be installed?
>>>>>
>>>>> I believe the wi::min_precision (t, UNSIGNED) <= sizeof (size_t) *
>>>>> CHAR_BIT test is now redundant.
>>>>>
>>>>> OTOH it was probably desired to allow -1 here?  A little looking back
>>>>> in time should tell.
>>>>
>>>> Ok, it started with r229922, where it was changed from:
>>>>
>>>>   if (tree_fits_uhwi_p (len) && p1 && p2)
>>>>     {
>>>>       const int i = strncmp (p1, p2, tree_to_uhwi (len));
>>>> ...
>>>>
>>>> to current version:
>>>>
>>>>     case CFN_BUILT_IN_STRNCMP:
>>>>       {
>>>>         bool const_size_p = host_size_t_cst_p (arg2, &s2);
>>>>
>>>> Thus I'm suggesting to change to back to it.
>>>>
>>>> Ready to be installed?
>>>
>>> Let's ask Richard.
>>
>> The idea with the:
>>
>>   wi::min_precision (t, UNSIGNED) <= sizeof (size_t) * CHAR_BIT
>>
>> test was to stop us attempting 64-bit size_t operations on ILP32 hosts.
>> I think we still want that.
>
> OK, so is the consensus to add tree_fits_uhwi_p predicate to the current
> wi::min_precision check, right?

Not sure.  If we have host_size_t_cst_p then we should have a corresponding
size_t host_size_t (const_tree) and should use those in pairs.  Not sure
why we have sth satisfying host_size_t_cst_p but not tree_fits_uhwi_p.
Is that wi::min_precision fault?  The way it is documented suggests that
it should be equal to tree_fits_uwhi_p ...

Richard.

> Thanks,
> Martin
>
>>
>> Thanks,
>> Richard
>>
>



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