Missing/wrong build dependencies for inline functions in HotSpot

[Keith McGuigan]

I can shepherd this through the hotspot-rt repository, where it will 
filter up to hotspot-main and then jdk8/hotspot.  I'll make a CR for 
this too.

http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot

--
- Keith

On 6/11/2012 6:10 AM, Volker Simonis wrote:
> Should this change be against
> http://hg.openjdk.java.net/jdk8/build/hotspot or better for
> http://hg.openjdk.java.net/hsx/hotspot-main/hotspot?
>
> On Mon, Jun 11, 2012 at 12:01 PM, Volker Simonis
> <volker.simonis at gmail.com>  wrote:
>> I found the problem!
>>
>> It's related to the use of precompiled headers. We need to use
>> '-fpch-deps' in order to get the full dependencies, otherwise all the
>> dependencies from the pch file are omitted.
>>
>> I'm currently preparing a webrev which fixes  the problem. It would be
>> nice if somebody could meanwhile open a bug for the problem (e.g.
>> "Usage of gcc with precompiled headers produces wrong build
>> dependencies") and provide a bug-id.
>>
>> Regards,
>> Volker
>>
>>
>> On Fri, Jun 8, 2012 at 7:50 PM, Volker Simonis<volker.simonis at gmail.com>  wrote:
>>> Yes, that's really strange. You're right, the dependency file should
>>> contain ".. the names of all the included files" (gcc -man page).
>>>
>>> So it seems to be a bug in gcc and how it handles '-MMD' although I
>>> couldn't find a bug report for it and I can't believe that nobody else
>>> has noticed this before. I've tried gcc 4.4.3 and 4.1.2 and they both
>>> produce a wrong dependency file which only contains the direct
>>> includes of the processed .cpp file (with "-c -MMD -MP -MF
>>> ../generated/dependencies/frame.o.d -o frame.o").
>>>
>>> If I compile with "-c -MM -MP -MF ../generated/dependencies/frame.o.d
>>> -o frame.o" the generated dependency file is much bigger and looks ok,
>>> but of course I get no object file. I also get he same wrong behavior
>>> for -MD vs -M. The only reason behind -MD and -MMD is that it "..can
>>> be used to generate a dependency output file as a side-effect of the
>>> compilation process" (from the GCC man page) - but that doesn't seem
>>> to work..
>>>
>>> Does anybody has an explanation for this behavior?
>>>
>>> Regards,
>>> Volker
>>>
>>> On Fri, Jun 8, 2012 at 6:25 PM, Keith McGuigan
>>> <keith.mcguigan at oracle.com>  wrote:
>>>>
>>>> I don't understand why gcc doesn't put frame_x86.inline.hpp into the
>>>> generated/dependencies/frame.o.d file.  Isn't the point of -MMD to calculate
>>>> the full closer of header files used for listing as a dependency?  Is this a
>>>> bug in gcc or are we using it wrong?
>>>>
>>>> I notice that Sun Studio compiler does put the arch-specific header file in
>>>> the generated dependency file.  Weird.
>>>>
>>>> --
>>>> - Keith
>>>>
>>>>
>>>> On 6/8/2012 11:58 AM, Volker Simonis wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> I've just stumbled across the problem that changing the implementation
>>>>> of an inline function in HotSpot does not necessarily rebuild all the
>>>>> call sites of that function. This is because because of the way how
>>>>> the build dependencies are handled within the HotSpot. As an example
>>>>> you may have a look at frame.cpp:
>>>>>
>>>>> frame.cpp includes frame.inline.hpp
>>>>> frame.inline.hpp includes frame_x86.inline.hpp
>>>>>
>>>>> However frame.cpp only depends on frame.inline.hpp directly (i.e.
>>>>> frame.cpp only includes frame.inline.hpp directly and this is where
>>>>> the dependencies generated by gcc with '-MMD' are computed from).
>>>>> So if an inline function in frame_x86.inline.hpp will be changed (e.g.
>>>>> the constructor frame::frame()), frame.cpp will not be recompiled in
>>>>> an incremental build, although it uses the constructor frame::frame().
>>>>> This makes incremental builds useless (or dangerous, depending on the
>>>>> view point) when inline functions are changed.
>>>>>
>>>>> I think this is a non-trivial problem which is deeply rooted in the
>>>>> way how C++ implements inlining and the way how inline functions are
>>>>> defined in HotSpot (i.e. .hpp, .inline.hpp,  _<cpu>.hpp and
>>>>> _<cpu>.inline.hpp files). I don't have a solution for it but just
>>>>> wanted to ask if somebody else already stumbled upon this problem
>>>>> and/or has solution for it?
>>>>>
>>>>> Regards,
>>>>> Volker