Re: [patch] Add a lexical block only when the callsite has source location info

[Richard Guenther <richard dot guenther at gmail dot com>]

On Tue, Jun 26, 2012 at 9:03 AM, Dehao Chen <dehao@google.com> wrote:
> Hi, Richard,
>
> You are right, setting UNKNOWN_LOCATION will not affect addr2line
> result. Here is the updated patch:
>
> Passed bootstrap and gcc regression tests.
>
> Is it ok for trunk?

Yes.

Thanks,
Richard.

> Thanks,
> Dehao
>
> Index: tree-inline.c
> ===================================================================
> --- tree-inline.c ? ? ? (revision 188926)
> +++ tree-inline.c ? ? ? (working copy)
> @@ -3836,8 +3836,7 @@
> ? /* Set input_location here so we get the right instantiation context
> ? ? ?if we call instantiate_decl from inlinable_function_p. ?*/
> ? saved_location = input_location;
> - ?if (gimple_has_location (stmt))
> - ? ?input_location = gimple_location (stmt);
> + ?input_location = gimple_location (stmt);
>
> ? /* From here on, we're only interested in CALL_EXPRs. ?*/
> ? if (gimple_code (stmt) != GIMPLE_CALL)
>
> On Mon, Jun 25, 2012 at 10:00 PM, Richard Guenther
> <richard.guenther@gmail.com> wrote:
>> On Mon, Jun 25, 2012 at 3:48 PM, Dehao Chen <dehao@google.com> wrote:
>>> Hi, Richard,
>>>
>>> Thanks for the prompt response.
>>>
>>> On Mon, Jun 25, 2012 at 8:02 PM, Richard Guenther
>>> <richard.guenther@gmail.com> wrote:
>>>> On Mon, Jun 25, 2012 at 1:43 PM, Dehao Chen <dehao@google.com> wrote:
>>>>> During function inlining, a lexical block is added for each cloned
>>>>> callee, and source info is attached to this block for addr2line to
>>>>> derive the inline stack.
>>>>
>>>> Well - the bug is then clearly
>>>>
>>>> ?/* Set input_location here so we get the right instantiation context
>>>> ? ? if we call instantiate_decl from inlinable_function_p. ?*/
>>>> ?saved_location = input_location;
>>>> ?if (gimple_has_location (stmt))
>>>> ? ?input_location = gimple_location (stmt)
>>>>
>>>> which retails input_location instead of setting it to UNKNOWN_LOCATION.
>>>>
>>>> Not adding a BLOCK will make debug information incorrect, no?
>>>
>>> The only case I can think of that gimple_has_location is false for
>>> call stmt is for function split.
>>>
>>> If we have function foo, which is split into:
>>>
>>> foo
>>> foo.part1
>>>
>>> And a callsite foo->foo.part1 is created in foo.
>>>
>>> If the ipa-inline decided to inline this callsite, for an instruction
>>> in foo.part1, it will have an inline stack of size 2. In the original
>>> buggy code, the bottom of the inline stack will be random. Using your
>>> proposed approach, the bottom of the inline stack would be
>>> UNKNOW_LOCATION, but still has two levels. For function split, this
>>> inline will not create any lexical block, but resumes the original
>>> lexical block before the split. Thus my change simply not add a new
>>> lexical block. Do you think this makes sense?
>>
>> I don't think it behaves sensibly for any other call without a location.
>> Basically you assume that this only happens for split functions but
>> I don't see why that should be true. ?Why would BLOCKs with
>> UNKOWN_LOCATION have any effect on addr2line anyways?
>> That seems to be something to check and fix.
>>
>> Richard.
>>
>>
>>> Thanks,
>>> Dehao
>>>
>>>
>>>>
>>>>> However, some callsites do not have source
>>>>> information attached to it. Adding a lexical block would be misleading
>>>>> in this case. E.g. If a function is split, when the split callsite is
>>>>> inlined back, the cloned callee should stay in the same lexical block
>>>>> with its caller. This patch ensures that lexical blocks are only added
>>>>> when the callsite has source location info in it.
>>>>>
>>>>> Bootstrapped and passed gcc regression tests.
>>>>>
>>>>> Is it ok for trunk?
>>>>
>>>> I'd rather see an unconditional set of input_location from gimple_location
>>>> of the statement.
>>>>
>>>> Richard.
>>>>
>>>>> Thanks,
>>>>> Dehao
>>>>>
>>>>> gcc/ChangeLog:
>>>>> 2012-06-25 ?Dehao Chen ?<dehao@google.com>
>>>>>
>>>>> ? ? ? ?* tree-profile.c: (expand_call_inline): Make a new lexical block only
>>>>
>>>> ? ?^^^^^
>>>> tree-inline.c
>>>>
>>>>> ? ? ? ?when the call stmt has source location.
>>>>>
>>>>> Index: gcc/tree-inline.c
>>>>> ===================================================================
>>>>> --- gcc/tree-inline.c ? (revision 188926)
>>>>> +++ gcc/tree-inline.c ? (working copy)
>>>>> @@ -3950,10 +3950,17 @@
>>>>> ? ? ?actual inline expansion of the body, and a label for the return
>>>>> ? ? ?statements within the function to jump to. ?The type of the
>>>>> ? ? ?statement expression is the return type of the function call. ?*/
>>>>> - ?id->block = make_node (BLOCK);
>>>>> - ?BLOCK_ABSTRACT_ORIGIN (id->block) = fn;
>>>>> - ?BLOCK_SOURCE_LOCATION (id->block) = input_location;
>>>>> - ?prepend_lexical_block (gimple_block (stmt), id->block);
>>>>> + ?if (gimple_has_location (stmt))
>>>>> + ? ?{
>>>>> + ? ? ?id->block = make_node (BLOCK);
>>>>> + ? ? ?BLOCK_ABSTRACT_ORIGIN (id->block) = fn;
>>>>> + ? ? ?BLOCK_SOURCE_LOCATION (id->block) = input_location;
>>>>
>>>> Please use gimple_location (stmt) instead of input_location (yes, I realize
>>>> its set from that).
>>>>
>>>>> + ? ? ?prepend_lexical_block (gimple_block (stmt), id->block);
>>>>> + ? ?}
>>>>> + ?else
>>>>> + ? ?{
>>>>> + ? ? ?id->block = gimple_block (stmt);
>>>>> + ? ?}
>>>>
>>>>> ? /* Local declarations will be replaced by their equivalents in this
>>>>> ? ? ?map. ?*/