On 2/16/21 10:11 AM, Tom de Vries wrote:
> The problem is caused by the odr code in checksum_ref_die, which skips
> checksum calculation for the children of odr types, with as unintended
> side-effect that it break the CK_BAD propagation to toplevel DIEs.
> 
> Fix this by making the skipping of the checksum calculation less intrusive.
> 
> Also, add the assert in partition_found_dups to catch this earlier and
> easier.
> 
> Unfortunately, the fix also means that the earlier reported performance
> improvement of odr on cc1, of 42.30%:
> ...
> $ ./dwz.master cc1 -o 1 -lnone
> $ ./diff.sh cc1 1
> .debug_info      red: 44.84%    111527248  61527733
> .debug_abbrev    red: 40.28%    1722726  1028968
> .debug_str       red: 0%        6609355  6609355
> total            red: 42.30%    119859329 69166056
> ...
> to 54.55%:
> ...
> $ ./dwz.master cc1 -o 2 -lnone --odr
> $ ./diff.sh cc1 2
> .debug_info      red: 57.46%    111527248  47449258
> .debug_abbrev    red: 75.08%    1722726  429434
> .debug_str       red: 0%        6609355  6609355
> total            red: 54.55%    119859329 54488047
> ...
> pretty much disappears:
> ...
> $ ./dwz.fix cc1 -o 3 -lnone --odr
> $ ./diff.sh cc1 3
> .debug_info      red: 45.44%    111527248  60858640
> .debug_abbrev    red: 42.88%    1722726  984084
> .debug_str       red: 0%        6609355  6609355
> total            red: 42.89%    119859329 68452079
> ...
> 

I managed to come up with a fix that doesn't suffer from this
performance regression.

Any comments?

Thanks,
- Tom