2014-06-03 15:56 GMT+04:00 Richard Biener <richard.guent...@gmail.com>:
> On Tue, Jun 3, 2014 at 1:36 PM, Ilya Enkovich <enkovich....@gmail.com> wrote:
>> 2014-06-03 13:45 GMT+04:00 Richard Biener <richard.guent...@gmail.com>:
>>> On Tue, Jun 3, 2014 at 9:23 AM, Ilya Enkovich <enkovich....@gmail.com>
>>> wrote:
>>>> Hi,
>>>>
>>>> This patch adjusts alloc-free removal algorithm in DCE to take into
>>>> account BUILT_IN_CHKP_BNDRET call returning bounds of allocated memory.
>>>>
>>>> Bootstrapped and tested on linux-x86_64.
>>>>
>>>> Thanks,
>>>> Ilya
>>>> --
>>>> gcc/
>>>>
>>>> 2014-06-03 Ilya Enkovich <ilya.enkov...@intel.com>
>>>>
>>>> * tree-ssa-dce.c: Include target.h.
>>>> (propagate_necessity): For free call fed by alloc check
>>>> bounds are also provided by the same alloc.
>>>> (eliminate_unnecessary_stmts): Handle BUILT_IN_CHKP_BNDRET
>>>> used by free calls.
>>>>
>>>> diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
>>>> index 13a71ce..59a0b71 100644
>>>> --- a/gcc/tree-ssa-dce.c
>>>> +++ b/gcc/tree-ssa-dce.c
>>>> @@ -73,6 +73,7 @@ along with GCC; see the file COPYING3. If not see
>>>> #include "flags.h"
>>>> #include "cfgloop.h"
>>>> #include "tree-scalar-evolution.h"
>>>> +#include "target.h"
>>>>
>>>> static struct stmt_stats
>>>> {
>>>> @@ -778,7 +779,23 @@ propagate_necessity (bool aggressive)
>>>> && DECL_BUILT_IN_CLASS (def_callee) == BUILT_IN_NORMAL
>>>> && (DECL_FUNCTION_CODE (def_callee) == BUILT_IN_MALLOC
>>>> || DECL_FUNCTION_CODE (def_callee) ==
>>>> BUILT_IN_CALLOC))
>>>> - continue;
>>>> + {
>>>> + tree retfndecl
>>>> + = targetm.builtin_chkp_function (BUILT_IN_CHKP_BNDRET);
>>>> + gimple bounds_def_stmt;
>>>> + tree bounds;
>>>> +
>>>> + /* For instrumented calls we should also check used
>>>> + bounds are returned by the same allocation call. */
>>>> + if (!gimple_call_with_bounds_p (stmt)
>>>> + || ((bounds = gimple_call_arg (stmt, 1))
>>>
>>> Please provide an abstraction for this - I seem to recall seeing multiple
>>> (variants) of this. Esp. repeated calls to the target hook above look
>>> expensive to me (generally it will not be needed).
>>>
>>> I'd like to see gimple_call_bndarg (stmt) to get rid of the "magic" 1 and
>>> I'd
>>> like to see sth similar to gimple_call_builtin_p, for example
>>> gimple_call_chkp_p (stmt, BUILT_IN_CHKP_BNDRET) doing the
>>> target hook invocation and the fndecl check.
>>
>> I do not see how to get rid of constant in gimple_call_arg call here.
>> What semantics does proposed gimple_call_bndarg have? It has to return
>> the first bounds arg but it's not clear from its name and function
>> seems to be very specialized.
>
> Ah, ok. I see now, so the code is ok as-is.
>
>>>
>>>> + && TREE_CODE (bounds) == SSA_NAME
>>>
>>> What about constant bounds? That shouldn't make the call necessary either?
>>
>> Yep, it would be useless.
>
> So please fix.
>
>>>
>>>> + && (bounds_def_stmt = SSA_NAME_DEF_STMT (bounds))
>>>> + && is_gimple_call (bounds_def_stmt)
>>>> + && gimple_call_fndecl (bounds_def_stmt) ==
>>>> retfndecl
>>>> + && gimple_call_arg (bounds_def_stmt, 0) == ptr))
>>>> + continue;
>>>
>>> So this all becomes
>>>
>>> if (!gimple_call_with_bounds_p (stmt)
>>> || ((bounds = gimple_call_bndarg (stmt))
>>> && TREE_CODE (bounds) == SSA_NAME
>>> && (bounds_def_stmt = SSA_NAME_DEF_STMT
>>> (bounds))
>>> && is_gimple_call (bounds_def_stmt)
>>> && gimple_call_chkp_p (bounds_def_stmt,
>>> BUILT_IN_CHKP_BNDRET)
>>> ...
>>>
>>> btw, I wonder how BUILT_IN_CHKP_BNDRET is in scope here but you
>>> need a target hook to compare the fndecl? Why isn't it enough to
>>> just check DECL_FUNCTION_CODE and DECL_BUILT_IN?
>>
>> Call is required because builtins for Pointer Bounds Checker are
>> provided by target depending on available features. That is why
>> gimple_call_builtin_p is not used. I may add new interface function
>> into tree-chkp.h as you propose (e.g. chkp_gimple_call_builtin_p). But
>> I do not see how it may speed-up the code. New function would still
>> need to switch by function code and compare with proper decl which is
>> basically what we have with target hook.
>
> I don't understand - does this mean the builtin calls are in the GIMPLE
> IL even though the target doesn't have the feature? Isn't the presence
> of the call enough?
Call is generated using function decl provided by target. Therefore we
do not know its code and has to compare using fndecl comparison.
>
>> It is possible to make faster if use the fact that all chkp builtins
>> codes (normal, not target ones) are consequent. Then we may just check
>> the range and use code as an index in array of chkp fndecls to compare
>> decls. Would it be OK to rely on builtin codes numbering?
>
> Yes, but that's not my point here. In the above code the target hook
> is called all the time, even if !gimple_call_with_bounds_p (). Providing
> a suitable abstraction (or simply relying on DECL_FUNCTION_CODE)
> should fix that.
Got it. Will fix.
Thanks,
Ilya
>
> Richard.
>
>> Ilya
>>
>>>
>>> Richard.
>>>
>>>> + }
>>>> }
>>>>
>>>> FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
>>>> @@ -1204,6 +1221,23 @@ eliminate_unnecessary_stmts (void)
>>>> && !gimple_plf (def_stmt, STMT_NECESSARY))
>>>> gimple_set_plf (stmt, STMT_NECESSARY, false);
>>>> }
>>>> + /* We did not propagate necessity for free calls fed
>>>> + by allocation function to allow unnecessary
>>>> + alloc-free sequence elimination. For instrumented
>>>> + calls it also means we did not mark bounds producer
>>>> + as necessary and it is time to do it in case free
>>>> + call is not removed. */
>>>> + if (gimple_call_with_bounds_p (stmt))
>>>> + {
>>>> + gimple bounds_def_stmt;
>>>> + tree bounds = gimple_call_arg (stmt, 1);
>>>> + gcc_assert (TREE_CODE (bounds) == SSA_NAME);
>>>> + bounds_def_stmt = SSA_NAME_DEF_STMT (bounds);
>>>> + if (bounds_def_stmt
>>>> + && !gimple_plf (bounds_def_stmt, STMT_NECESSARY))
>>>> + gimple_set_plf (bounds_def_stmt, STMT_NECESSARY,
>>>> + gimple_plf (stmt, STMT_NECESSARY));
>>>> + }
>>>> }
>>>>
>>>> /* If GSI is not necessary then remove it. */
>>>> @@ -1216,6 +1250,7 @@ eliminate_unnecessary_stmts (void)
>>>> else if (is_gimple_call (stmt))
>>>> {
>>>> tree name = gimple_call_lhs (stmt);
>>>> + tree retfn = targetm.builtin_chkp_function
>>>> (BUILT_IN_CHKP_BNDRET);
>>>>
>>>> notice_special_calls (stmt);
>>>>
>>>> @@ -1233,7 +1268,9 @@ eliminate_unnecessary_stmts (void)
>>>> && DECL_FUNCTION_CODE (call) != BUILT_IN_CALLOC
>>>> && DECL_FUNCTION_CODE (call) != BUILT_IN_ALLOCA
>>>> && (DECL_FUNCTION_CODE (call)
>>>> - != BUILT_IN_ALLOCA_WITH_ALIGN))))
>>>> + != BUILT_IN_ALLOCA_WITH_ALIGN)))
>>>> + /* Avoid doing so for bndret calls for the same reason.
>>>> */
>>>> + && (!retfn || gimple_call_fndecl (stmt) != retfn))
>>>> {
>>>> something_changed = true;
>>>> if (dump_file && (dump_flags & TDF_DETAILS))
