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

[Xinliang David Li via llvm-dev]

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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