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Re: [PATCH, PR63995, CHKP] Use single static bounds var for varpool nodes sharing asm name


2014-11-25 12:43 GMT+03:00 Richard Biener <richard.guenther@gmail.com>:
> On Tue, Nov 25, 2014 at 9:45 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>> Hi,
>>
>> This patch partly fixes PR bootstrap/63995 by avoiding duplicating static bounds vars.  With this fix bootstrap still fails at stage 2 and 3 comparison.
>>
>> Bootstrapped and checked on x86_64-unknown-linux-gnu.  OK for trunk?
>>
>> Thanks,
>> Ilya
>> --
>> gcc/
>>
>> 2014-11-25  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         PR bootstrap/63995
>>         * tree-chkp (chkp_make_static_bounds): Share bounds var
>>         between nodes sharing assembler name.
>>
>> gcc/testsuite
>>
>> 2014-11-25  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         PR bootstrap/63995
>>         * g++.dg/dg.exp: Add mpx-dg.exp.
>>         * g++.dg/pr63995-1.C: New.
>>
>>
>> diff --git a/gcc/testsuite/g++.dg/dg.exp b/gcc/testsuite/g++.dg/dg.exp
>> index 14beae1..44eab0c 100644
>> --- a/gcc/testsuite/g++.dg/dg.exp
>> +++ b/gcc/testsuite/g++.dg/dg.exp
>> @@ -18,6 +18,7 @@
>>
>>  # Load support procs.
>>  load_lib g++-dg.exp
>> +load_lib mpx-dg.exp
>>
>>  # If a testcase doesn't have special options, use these.
>>  global DEFAULT_CXXFLAGS
>> diff --git a/gcc/testsuite/g++.dg/pr63995-1.C b/gcc/testsuite/g++.dg/pr63995-1.C
>> new file mode 100644
>> index 0000000..82e7606
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/pr63995-1.C
>> @@ -0,0 +1,16 @@
>> +/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
>> +/* { dg-require-effective-target mpx } */
>> +/* { dg-options "-O2 -g -fcheck-pointer-bounds -mmpx" } */
>> +
>> +int test1 (int i)
>> +{
>> +  extern const int arr[10];
>> +  return arr[i];
>> +}
>> +
>> +extern const int arr[10];
>> +
>> +int test2 (int i)
>> +{
>> +  return arr[i];
>> +}
>> diff --git a/gcc/tree-chkp.c b/gcc/tree-chkp.c
>> index 3e38691..d425084 100644
>> --- a/gcc/tree-chkp.c
>> +++ b/gcc/tree-chkp.c
>> @@ -2727,9 +2727,29 @@ chkp_make_static_bounds (tree obj)
>>    /* First check if we already have required var.  */
>>    if (chkp_static_var_bounds)
>>      {
>> -      slot = chkp_static_var_bounds->get (obj);
>> -      if (slot)
>> -       return *slot;
>> +      /* If there is a symbol sharing assembler name with obj,
>> +        we may use its bounds.  */
>> +      if (TREE_CODE (obj) == VAR_DECL)
>> +       {
>> +         varpool_node *node = varpool_node::get_create (obj);
>> +
>> +         while (node->previous_sharing_asm_name)
>> +           node = (varpool_node *)node->previous_sharing_asm_name;
>> +
>> +         while (node)
>> +           {
>> +             slot = chkp_static_var_bounds->get (node->decl);
>> +             if (slot)
>> +               return *slot;
>> +             node = (varpool_node *)node->next_sharing_asm_name;
>> +           }
>
> Hum.  varpool_node::get returns the ultimate alias target thus the
> walking shouldn't be necessary.  Just
>
>   node = varpool_node::get_create (obj);
>   slot = chkp_static_var_bounds->get (node->decl);
>   if (slot)
>     return *slot;
>
> and then making sure to set the decl also for node->decl.  I suppose
> it really asks for making chkp_static_var_bounds->get based on
> a varpool node and not a decl so you consistently use the ultimate
> alias target.

varpool_node::get just returns symtab_node::get which returns
decl->decl_with_vis.symtab_node - thus no aliases walkthrough. Also
none of two varpool_nodes is an alias. The only connection between
these nodes seems to be {next,previous}_sharing_asm_name. Here is how
these nodes look:

(gdb) p *$2
$3 = {<symtab_node> = {type = SYMTAB_VARIABLE, resolution =
LDPR_UNKNOWN, definition = 0, alias = 0, weakref = 0,
cpp_implicit_alias = 0, analyzed = 0, writeonly = 0,
refuse_visibility_changes = 0, externally_visible = 0,
    no_reorder = 0, force_output = 0, forced_by_abi = 0, unique_name =
0, implicit_section = 0, body_removed = 1, used_from_other_partition =
0, in_other_partition = 0, address_taken = 0, in_init_priority_hash =
0,
    need_lto_streaming = 0, offloadable = 0, order = 3, decl =
0x7ffff7dd2cf0, next = 0x7ffff7f46200, previous = 0x7ffff7dd67a8,
next_sharing_asm_name = 0x0, previous_sharing_asm_name =
0x7ffff7f46200, same_comdat_group = 0x0,
    ref_list = {references = 0x0, referring = {m_vec = 0x23856b0}},
alias_target = 0x0, lto_file_data = 0x0, aux = 0x0, x_comdat_group =
0x0, x_section = 0x0}, output = 0, need_bounds_init = 0,
dynamically_initialized = 0,
  tls_model = TLS_MODEL_NONE, used_by_single_function = 0}

(gdb) p *$5
$6 = {<symtab_node> = {type = SYMTAB_VARIABLE, resolution =
LDPR_UNKNOWN, definition = 0, alias = 0, weakref = 0,
cpp_implicit_alias = 0, analyzed = 0, writeonly = 0,
refuse_visibility_changes = 0, externally_visible = 0,
    no_reorder = 0, force_output = 0, forced_by_abi = 0, unique_name =
0, implicit_section = 0, body_removed = 1, used_from_other_partition =
0, in_other_partition = 0, address_taken = 0, in_init_priority_hash =
0,
    need_lto_streaming = 0, offloadable = 0, order = 2, decl =
0x7ffff7dd2bd0, next = 0x7ffff7dd6620, previous = 0x7ffff7f46300,
next_sharing_asm_name = 0x7ffff7f46300, previous_sharing_asm_name =
0x0, same_comdat_group = 0x0,
    ref_list = {references = 0x0, referring = {m_vec = 0x238bdd0}},
alias_target = 0x0, lto_file_data = 0x0, aux = 0x0, x_comdat_group =
0x0, x_section = 0x0}, output = 0, need_bounds_init = 0,
dynamically_initialized = 0,
  tls_model = TLS_MODEL_NONE, used_by_single_function = 0}


Thanks,
Ilya

>
> Richard.
>
>> +       }
>> +      else
>> +       {
>> +         slot = chkp_static_var_bounds->get (obj);
>> +         if (slot)
>> +           return *slot;
>> +       }
>>      }
>>
>>    /* Build decl for bounds var.  */


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