[RFC] zstd as a compression algorithm for LTO

[Jan Hubicka]

> On 6/20/19 12:58 PM, Thomas Koenig wrote:
> > Am 20.06.19 um 11:07 schrieb Martin Liška:
> >> On the contrary, decompression
> >> of zstd with zlib will end with:
> >> lto1: internal compiler error: compressed stream: data error
> > 
> > Sogenerating object files on one system and trying to read them
> > on another system which does not happen to have a particular
> > library installed would lead to failure?  If that's the case,
> > I am not sure that this is a good way of handling things.
> 
> Yes, but LTO bytecode is not supposed to be a distributable format.

In longer term it should be.  We ought to make it host independent and
stable at least within major releases.
I guess it is still OK to make zstd enabled host build require zstd
enabled gcc elsewhere. Just the error message should be more informative
which I think is not hard to do - both zstd and zlip should have
recognizable header.

Other option is to put this into some common place per file.

Honza
> 
> Martin