Re: [PATCH] offline gcda profile processing tool

[Christophe Lyon <christophe.lyon@linaro.org>]

On 11 July 2014 10:07, Richard Biener <richard.guenther@gmail.com> wrote:
> On Mon, May 5, 2014 at 7:17 PM, Rong Xu <xur@google.com> wrote:
>> Here is the updated patch. The difference with patch set 3 is
>> (1) use the gcov-counter.def for scaling operation.
>> (2) fix wrong scaling function for time-profiler.
>>
>> passed with bootstrap, profiledboostrap and SPEC2006.
>
> One of the patches breaks bootstrap for me:
>
> /space/rguenther/src/svn/trunk/gcc/../libgcc/libgcov.h:184: error: ISO
> C++ forbids zero-size array ‘ctrs’
> make[3]: *** [libgcov-util.o] Error 1
>
> host compiler is gcc 4.3.4
>
> Richard.
>

On my side, commit 212448 breaks the cross-build of GCC for targets
using newlib:
* arm-none-eabi
* aarch64-none-elf
/usr/include/sys/stat.h: In function <80><98>void
gcov_output_files(const char*, gcov_info*)<80><99>:
/usr/include/sys/stat.h:317: error: too few arguments to function
<80><98>int mkdir(const char*, __mode_t)<80><99>
/tmp/1392958_1.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/gcov-tool.c:96:
error: at this point in file
make[2]: *** [gcov-tool.o] Error 1

Christophe.

>> Thanks,
>>
>> -Rong
>>
>> On Thu, May 1, 2014 at 3:37 PM, Rong Xu <xur@google.com> wrote:
>>> Hi, Honza,
>>>
>>> Please find the new patch in the attachment. This patch integrated
>>> your earlier suggestions. The noticeable changes are:
>>> (1) build specialized object for libgcov-driver.c and libgcov-merge.c
>>> and link into gcov-tool, rather including the source file.
>>> (2) split some gcov counter definition code to gcov-counter.def to
>>> avoid code duplication.
>>> (3) use a macro for gcov_read_counter(), so gcov-tool can use existing
>>> code in libgcov-merge.c with minimal change.
>>>
>>> This patch does not address the suggestion of creating a new directory
>>> for libgcov. I agree with you that's a much better
>>> and cleaner structure we should go for. We can do that in follow-up patches.
>>>
>>> I tested this patch with boostrap and profiledbootstrap. Other tests
>>> are on-going.
>>>
>>> Thanks,
>>>
>>> -Rong
>>>
>>> On Wed, Apr 16, 2014 at 8:34 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
>>>>> GCOT_TOOL needs to use this function to read the string in gcda file
>>>>> to memory to construct gcov_info objects.
>>>>> As you noticed, gcov runtime does not need this interface. But
>>>>> gcov-tool links with gcov runtime and it also uses the function.
>>>>> We could make it available in gcov_runtime, but that will slightly
>>>>> increase the memory footprint.
>>>>
>>>> Yep, it is not really pretty. I wrote bellow some plan how things may be
>>>> structured in more convenient way.  Any work in that direction would be welcome.
>>>>>
>>>>> The planned new functions for trunk version is: (1) overlap score b/w
>>>>> two profiles (2) better dumping (top hot objects/function/counters)
>>>>> and statistics.
>>>>> Once this basic version is in, we can start to add the new functionality.
>>>>
>>>> Sounds good. I assume the autoFDO does not go via gcov tool but rather uses
>>>> custom reader of profile data at GCC side?
>>>> I wonder, are there any recent overview papers/slides/text of design of AutoFDO
>>>> and other features to be merged?
>>>> I remember the talk from GCC Summit and I did read some of pre-LTO LIPO
>>>> sources & papers, but it would be nice to have somethin up to date.
>>>>>
>>>>> libgcov-util.o is built in gcc/ directory, rather in libgcc.
>>>>> It's directly linked to gcov-tool.
>>>>> So libgcov-util.o is built for HOST, not TARGET.
>>>>> With makefile changes, we can built HOST version of libgcov-driver.o
>>>>> and libgcov-merge.o.
>>>>> I also need to make some static functions/variables public.
>>>>
>>>> I suppose that can go with IN_GCOV_TOOL ifdef.
>>>>
>>>> So we currently have basic gcov io handling in gcc/gcov-io.c that is borrowed
>>>> by libgcc/libgcov* code.  We also will get libgcov-util.c in libgcc directory
>>>> that is actually borrowed by by gcc/gcov-tool.c code.
>>>>
>>>> We now have one runtime using STDIO for streaming and kernel has custom version
>>>> that goes via /proc interface (last time I looked).  We added some abstraction
>>>> into libgcov-interface that is the part that relies on STDIO, partly via gcov-io.c
>>>> code and now we have in-memory handling code in libgcov-util.
>>>>
>>>> I guess it would make most sentse to put all the gcov code into a new directory
>>>> (libgcov) and make it stand-alone library that can be configured
>>>> 1) for stdio based runtime as we do not
>>>> 2) for runtime missing the interface and relyin on user providing it
>>>> 3) for use within gcov file manipulation tools with reorg of
>>>> GCC/gcov/gcov-dump/gcov-tool to all use the same low-level interfaces.
>>>> In a longer term, I would like to make FDO profiling intstrumentation to happen
>>>> at linktime. For that I need to make the instrumentation code (minimal spaning
>>>> tree & friends) to work w/o cgraph that would ideally be done in a shared
>>>> implementation
>>>>> > Won't this get wrong answer when counters[0] is not the same?
>>>>> > I would expected the merging code to compare the counters first. Similarly for delta counter.
>>>>>
>>>>> These *_op functions are for scaling only. So there is only one
>>>>> profile involved (thus there is no comparison).
>>>>> The merge handles are in libgcov-merge.c which have the code to handle
>>>>> mismatched profile targets.
>>>>
>>>> I see, OK then.
>>>>> >
>>>>> > Adding correct rounding may actually make difference for Martin's startup time work.
>>>>>
>>>>> Do you mean to use something like in RDIV macro?
>>>>
>>>> Yes.
>>>>
>>>> Honza