llvm dev - May 2017 - bugpoint, LLVM tools (opt, llc, etc), and symbolizing costs

test/BugPoint/metadata.ll
Takes about 6 seconds to run if llvm-symbolizer isn't present
13 seconds with debug info
1m30s with split DWARF/Fission

So, couple of things:
1) llvm-symbolizer is /really slow/ on split-dwarf files...
2) Why are stack traces even attempted when using bugpoint? Even if it's
just the 6->13s slowdown, that's still halving the speed of bugpoint in
the
presence of llvm-symbolizer+debug info (I didn't test in the presence of
llvm-symbolizer but no debug info)?

It doesn't look like the LLVM tools have any way to disable
symbolization/stack trace/crash handling. Is that correct? Is there a flag
somewhere that I missed?

Would it be worth adding such a flag and passing it from bugpoint to the
various tools it invokes?

(anyone interested in looking at exactly what makes llvm-symbolizer /so/
much slower on split DWARF? I guess that's probably something for me to
look at, really (though I checked that it's at least not due to my recent
changes - but there have been some other refactorings here recently too) -
but figured I'd check)
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We have the LLVM_DISABLE_CRASH_REPORT environment variable, but that's more
about whether we should do crash reporting or not.

It would be pretty reasonable to have another one to disable all this
stuff. It would also be reasonable to have a cmake option that compiles
this stuff away, since it basically never works on user machines that don't
have debug info.

On Tue, May 23, 2017 at 2:02 PM, David Blaikie via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> test/BugPoint/metadata.ll
> Takes about 6 seconds to run if llvm-symbolizer isn't present
> 13 seconds with debug info
> 1m30s with split DWARF/Fission
>
> So, couple of things:
> 1) llvm-symbolizer is /really slow/ on split-dwarf files...
> 2) Why are stack traces even attempted when using bugpoint? Even if
it's
> just the 6->13s slowdown, that's still halving the speed of bugpoint
in the
> presence of llvm-symbolizer+debug info (I didn't test in the presence
of
> llvm-symbolizer but no debug info)?
>
> It doesn't look like the LLVM tools have any way to disable
> symbolization/stack trace/crash handling. Is that correct? Is there a flag
> somewhere that I missed?
>
> Would it be worth adding such a flag and passing it from bugpoint to the
> various tools it invokes?
>
> (anyone interested in looking at exactly what makes llvm-symbolizer /so/
> much slower on split DWARF? I guess that's probably something for me to
> look at, really (though I checked that it's at least not due to my
recent
> changes - but there have been some other refactorings here recently too) -
> but figured I'd check)
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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On Tue, May 23, 2017 at 2:40 PM Reid Kleckner <rnk at google.com> wrote:
> We have the LLVM_DISABLE_CRASH_REPORT environment variable, but that's
> more about whether we should do crash reporting or not.
>
> It would be pretty reasonable to have another one to disable all this
> stuff. It would also be reasonable to have a cmake option that compiles
> this stuff away, since it basically never works on user machines that
don't
> have debug info.
>
Fair - any thoughts of having a dynamic option (rather than a build time
option) so that things like bugpoint could disable it for runs of tools,
but the tools itself could still have the functionality for once you finish
running bugpoint and then run the same command manually?

>
> On Tue, May 23, 2017 at 2:02 PM, David Blaikie via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> test/BugPoint/metadata.ll
>> Takes about 6 seconds to run if llvm-symbolizer isn't present
>> 13 seconds with debug info
>> 1m30s with split DWARF/Fission
>>
>> So, couple of things:
>> 1) llvm-symbolizer is /really slow/ on split-dwarf files...
>> 2) Why are stack traces even attempted when using bugpoint? Even if
it's
>> just the 6->13s slowdown, that's still halving the speed of
bugpoint in the
>> presence of llvm-symbolizer+debug info (I didn't test in the
presence of
>> llvm-symbolizer but no debug info)?
>>
>> It doesn't look like the LLVM tools have any way to disable
>> symbolization/stack trace/crash handling. Is that correct? Is there a
flag
>> somewhere that I missed?
>>
>> Would it be worth adding such a flag and passing it from bugpoint to
the
>> various tools it invokes?
>>
>> (anyone interested in looking at exactly what makes llvm-symbolizer
/so/
>> much slower on split DWARF? I guess that's probably something for
me to
>> look at, really (though I checked that it's at least not due to my
recent
>> changes - but there have been some other refactorings here recently
too) -
>> but figured I'd check)
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>
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