[llvm-dev] PGO, zlib and 'default.profraw'

[Xinliang David Li via llvm-dev]

I think that is a good idea.

David

On Tue, Jul 18, 2017 at 11:37 AM, Justin Bogner <mail at justinbogner.com>
wrote:

> Can we improve the error message here? We should be able to check
> zlib::isAvailable and give an error like "profile uses zlib compression
> but the profile reader was built without zlib support" or so in this
> case.
>
> Xinliang David Li via llvm-dev <llvm-dev at lists.llvm.org> writes:
> > The __llvm_prf_names section is compressed but your llvm-profdata tool is
> > probably not built with zlib enabled.
> >
> > To disable compression, use option -mllvm -enable-name-compression=false
> >  in your instrumentation build.
> >
> > David
> >
> > On Tue, Jul 18, 2017 at 7:05 AM, ORiordan, Martin via llvm-dev <
> > llvm-dev at lists.llvm.org> wrote:
> >
> >> We are trying to get PGO working for our embedded out-of-tree target,
> but
> >> the utility ‘llvm-profdata’ does not like the data we are giving it.
> >>
> >>
> >>
> >> Because this is not a hosted environment, we have to off-chip the
> >> profiling data ourselves, and although the data looks okay,
> ‘llvm-profdata’
> >> reports the following error:
> >>
> >>
> >>
> >> *llvm-profdata show -all-functions -counts -detailed-summary -text
> >> -static-func-full-module-prefix ~/Downloads/default.profraw*
> >>
> >> error: ~/Downloads/default.profraw: Failed to uncompress data (zlib)
> >>
> >>
> >>
> >> But even for a hosted system, it is not clear to me where ‘zlib’ gets
> >> involved in compressing the data.  The start of our data looks like:
> >>
> >>
> >>
> >> *hexdump -C default.profraw*
> >>
> >> 00000000  81 52 66 6f 72 70 6c ff  04 00 00 00 00 00 00
> >>
> >> 00  |.Rforpl.........|
> >>
> >> 00000010  3c 00 00 00 00 00 00 00  28 01 00 00 00 00 00
> >>
> >> 00  |<.......(.......|
> >>
> >>
> >>
> >> Which looks valid for Little-Endian, 32-bit and LLVM v4.0.
> >>
> >>
> >>
> >> What do we need to do to prepare this raw data from the device into the
> >> form that ‘llvm-profdata’ needs to see?
> >>
> >>
> >>
> >> Thanks,
> >>
> >>
> >>
> >>             MartinO
> >>
> >>
> >>
> >>
> >>
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