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Re: [PATCH, MPX, 2/X] Pointers Checker [7/25] Suppress BUILT_IN_CHKP_ARG_BND optimizations.


Richard Biener <richard.guenther@gmail.com> wrote:
>On Thu, Oct 31, 2013 at 10:02 AM, Ilya Enkovich
><enkovich.gnu@gmail.com> wrote:
>> Hi,
>>
>> Here is a patch which hadles the problem with optimization of
>BUILT_IN_CHKP_ARG_BND calls.  Pointer Bounds Checker expects that
>argument of this call is a default SSA_NAME of the PARM_DECL whose
>bounds we want to get.  The problem is in optimizations which may
>replace arg with it's copy or a known value.  This patch suppress such
>modifications.
>
>This doesn't seem like a good fix.  I suppose you require the same on
>RTL, that is, have the incoming arg reg coalesced with the use?
>In that case better set SSA_NAME_OCCURS_IN_ABNORMAL_PHI.

Btw, I would have chosen

P_2 = __builtin_xyz (p_1, bound)
Call (p_2)

Thus make the builtins a transparent pass-through which effectively binds parameter to their bound, removing the need for the artificial arguments and making propagations a non.issue

Also, how does the feature interact with other extensions such as nested functions or optimizations like inlining?

Richard.


>Richard.
>
>> Thanks,
>> Ilya
>> --
>>
>> gcc/
>>
>> 2013-10-28  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         * tree-into-ssa.c: Include "target.h"
>>         (rewrite_update_stmt): Skip BUILT_IN_CHKP_ARG_BND calls.
>>         * tree-ssa-dom.c: Include "target.h"
>>         (cprop_into_stmt): Skip BUILT_IN_CHKP_ARG_BND calls.
>>
>>
>> diff --git a/gcc/tree-into-ssa.c b/gcc/tree-into-ssa.c
>> index 981e9f4..8d48f6d 100644
>> --- a/gcc/tree-into-ssa.c
>> +++ b/gcc/tree-into-ssa.c
>> @@ -46,6 +46,7 @@ along with GCC; see the file COPYING3.  If not see
>>  #include "params.h"
>>  #include "diagnostic-core.h"
>>  #include "tree-into-ssa.h"
>> +#include "target.h"
>>
>>
>>  /* This file builds the SSA form for a function as described in:
>> @@ -1921,8 +1922,14 @@ rewrite_update_stmt (gimple stmt,
>gimple_stmt_iterator gsi)
>>      }
>>
>>    /* Rewrite USES included in OLD_SSA_NAMES and USES whose
>underlying
>> -     symbol is marked for renaming.  */
>> -  if (rewrite_uses_p (stmt))
>> +     symbol is marked for renaming.
>> +     Skip calls to BUILT_IN_CHKP_ARG_BND whose arg should never be
>> +     renamed.  */
>> +  if (rewrite_uses_p (stmt)
>> +      && !(flag_check_pointer_bounds
>> +          && (gimple_code (stmt) == GIMPLE_CALL)
>> +          && gimple_call_fndecl (stmt)
>> +          == targetm.builtin_chkp_function (BUILT_IN_CHKP_ARG_BND)))
>>      {
>>        if (is_gimple_debug (stmt))
>>         {
>> diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
>> index 211bfcf..445278a 100644
>> --- a/gcc/tree-ssa-dom.c
>> +++ b/gcc/tree-ssa-dom.c
>> @@ -45,6 +45,7 @@ along with GCC; see the file COPYING3.  If not see
>>  #include "params.h"
>>  #include "tree-ssa-threadedge.h"
>>  #include "tree-ssa-dom.h"
>> +#include "target.h"
>>
>>  /* This file implements optimizations on the dominator tree.  */
>>
>> @@ -2266,6 +2267,16 @@ cprop_into_stmt (gimple stmt)
>>    use_operand_p op_p;
>>    ssa_op_iter iter;
>>
>> +  /* Call used to obtain bounds of input arg by Pointer Bounds
>Checker
>> +     should not be optimized.  Argument of the call is a default
>> +     SSA_NAME of PARM_DECL.  It should never be replaced by value. 
>*/
>> +  if (flag_check_pointer_bounds && gimple_code (stmt) ==
>GIMPLE_CALL)
>> +    {
>> +      tree fndecl = gimple_call_fndecl (stmt);
>> +      if (fndecl == targetm.builtin_chkp_function
>(BUILT_IN_CHKP_ARG_BND))
>> +       return;
>> +    }
>> +
>>    FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_USE)
>>      cprop_operand (stmt, op_p);
>>  }



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