Richard Biener <richard.guent...@gmail.com> writes:
> On Mon, Oct 31, 2016 at 10:10 AM, Martin Liška <mli...@suse.cz> wrote:
>> On 10/31/2016 01:12 AM, Richard Sandiford wrote:
>>> Richard Biener <richard.guent...@gmail.com> writes:
>>>> On Thu, Oct 27, 2016 at 5:06 PM, Martin Liška <mli...@suse.cz> wrote:
>>>>> On 10/27/2016 03:35 PM, Richard Biener wrote:
>>>>>> On Thu, Oct 27, 2016 at 9:41 AM, Martin Liška <mli...@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.
It's the other way around: something can satisfy tree_fits_uhwi_p
(i.e. fit within a uint64_t) but not fit within the host's size_t.
The kind of case I'm thinking of is:
strncmp ("fi", "fo", (1L << 32) + 1)
for an ILP32 host and LP64 target. There's a danger that by passing
the uint64_t value (1L << 32) + 1 to the host's strncmp that we'd
truncate it to 1, giving the wrong result.
Thanks,
Richard
