This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [GOOGLE] More strict checking for call args
- From: Xinliang David Li <davidxl at google dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Dehao Chen <dehao at google dot com>, Duncan Sands <baldrick at free dot fr>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 7 Jun 2013 06:30:47 -0700
- Subject: Re: [GOOGLE] More strict checking for call args
- References: <CAO2gOZWs7maFPDo=EZUe1mPARfNFxxnA5Yg3z0Wo0WS1+2ji2Q at mail dot gmail dot com> <51A85C16 dot 1030505 at free dot fr> <CAAkRFZL7aPp9WSxsj1yaujdBWrs91D=H0d_+KxVcgnh=xnt7Ng at mail dot gmail dot com> <CAO2gOZUZ0xTXoMPmLyhsCRkyFQehu7A7EiuqS1E40hBvd8yvxQ at mail dot gmail dot com> <CAFiYyc2q4nGUWNqDbqcpMunEPr-jQN0f2==h-rmMUCjqTWtTUw at mail dot gmail dot com> <CAO2gOZXqae0ju2nMK=f_XSKZFMOscdmL__P=MYf7x01BBs=jOw at mail dot gmail dot com> <CAAkRFZK4rfGvcaJ2PH34TGXtGaC41Wk8SeJ5hEyiC_eU9LTiTA at mail dot gmail dot com> <CAO2gOZViTTifco=SJ8sFqGjdAzg2h8Dzs87xtLa0ZVGaAJzGLg at mail dot gmail dot com> <20130606141124 dot GB30912 at virgil dot suse> <CAO2gOZWYMEa5y9F++nrfZm9JapTP2kCSEeHv-ad_aPNvRdS4-A at mail dot gmail dot com> <CAFiYyc2GTpRWx0iAaqmT9vq-fqACzAHwG+wixkAbu9iiVst_+Q at mail dot gmail dot com>
On Fri, Jun 7, 2013 at 2:05 AM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Thu, Jun 6, 2013 at 5:10 PM, Dehao Chen <dehao@google.com> wrote:
>> Hi, Martin,
>>
>> Yes, your patch can fix my case. Thanks a lot for the fix.
>>
>> With the fix, value profiling will still promote the wrong indirect
>> call target. Though it will not be inlining, but it results in an
>> additional check. How about in check_ic_target, after calling
>> gimple_check_call_matching_types, we also check if number of args
>> match number of params in target->symbol.decl?
>
> I wonder what's the point in the gimple_check_call_matching_types check
> in the profiling case. It's at least no longer
>
> /* Perform sanity check on the indirect call target. Due to race conditions,
> false function target may be attributed to an indirect call site. If the
> call expression type mismatches with the target function's type, expand_call
> may ICE.
>
> because since the introduction of gimple_call_fntype we will _not_ ICE.
>
> Thus I argue that check_ic_target should be even removed instead of
> enhancing it!
>
Another reason is what Dehao had mentioned -- wrong target leads to
useless transformation.
> How does IC profiling determine the called target? That is, what does it
> do when the target is not always the same? (because the checking code
> talks about race conditions for example)
The race condition is the happening at instrumentation time -- the
indirect call counters are not thread local. We have seen this a lot
in the past that a totally bogus target is attributed to a indirect
callsite.
thanks,
David
>
> Richard.
>
>
>> Thanks,
>> Dehao
>>
>>
>> On Thu, Jun 6, 2013 at 7:11 AM, Martin Jambor <mjambor@suse.cz> wrote:
>>>
>>> Hi,
>>>
>>> On Tue, Jun 04, 2013 at 05:19:02PM -0700, Dehao Chen wrote:
>>> > attached is a testcase that would cause problem when source has changed:
>>> >
>>> > $ g++ test.cc -O2 -fprofile-generate -DOLD
>>> > $ ./a.out
>>> > $ g++ test.cc -O2 -fprofile-use
>>> > test.cc:34:1: internal compiler error: in operator[], at vec.h:815
>>> > }
>>> > ^
>>> > 0x512740 vec<tree_node*, va_heap, vl_embed>::operator[](unsigned int)
>>> > ../../gcc/vec.h:815
>>> > 0x512740 vec<tree_node*, va_heap, vl_ptr>::operator[](unsigned int)
>>> > ../../gcc/vec.h:1244
>>> > 0xf24464 vec<tree_node*, va_heap, vl_embed>::operator[](unsigned int)
>>> > ../../gcc/vec.h:815
>>> > 0xf24464 vec<tree_node*, va_heap, vl_ptr>::operator[](unsigned int)
>>> > ../../gcc/vec.h:1244
>>> > 0xf24464 ipa_get_indirect_edge_target_1
>>> > ../../gcc/ipa-cp.c:1535
>>> > 0x971b9a estimate_edge_devirt_benefit
>>> > ../../gcc/ipa-inline-analysis.c:2757
>>>
>>> Hm, this seems rather like an omission in ipa_get_indirect_edge_target_1.
>>> Since it is called also from inlining, we can have parameter count
>>> mismatches... and in fact in non-virtual paths of that function we do
>>> check that we don't. Because all callers have to pass known_vals
>>> describing all formal parameters of the inline tree root, we should
>>> apply the fix below (I've only just started running a bootstrap and
>>> testsuite on x86_64, though).
>>>
>>> OTOH, while I understand that FDO can change inlining sufficiently so
>>> that this error occurs, IMHO this should not be caused by outdated
>>> profiles but there is somewhere a parameter mismatch in the source.
>>>
>>> Dehao, can you please check that this patch helps?
>>>
>>> Richi, if it does and the patch passes bootstrap and tests, is it OK
>>> for trunk and 4.8 branch?
>>>
>>> Thanks and sorry for the trouble,
>>>
>>> Martin
>>>
>>>
>>> 2013-06-06 Martin Jambor <mjambor@suse.cz>
>>>
>>> * ipa-cp.c (ipa_get_indirect_edge_target_1): Check that param_index is
>>> within bounds at the beginning of the function.
>>>
>>> Index: src/gcc/ipa-cp.c
>>> ===================================================================
>>> --- src.orig/gcc/ipa-cp.c
>>> +++ src/gcc/ipa-cp.c
>>> @@ -1481,7 +1481,8 @@ ipa_get_indirect_edge_target_1 (struct c
>>> tree otr_type;
>>> tree t;
>>>
>>> - if (param_index == -1)
>>> + if (param_index == -1
>>> + || known_vals.length () <= (unsigned int) param_index)
>>> return NULL_TREE;
>>>
>>> if (!ie->indirect_info->polymorphic)
>>> @@ -1516,8 +1517,7 @@ ipa_get_indirect_edge_target_1 (struct c
>>> t = NULL;
>>> }
>>> else
>>> - t = (known_vals.length () > (unsigned int) param_index
>>> - ? known_vals[param_index] : NULL);
>>> + t = NULL;
>>>
>>> if (t &&
>>> TREE_CODE (t) == ADDR_EXPR