[PATCH 0/5] RFC: Overhaul of diagnostics (v2)

Michael Matz matz@suse.de
Wed Sep 23 13:36:00 GMT 2015


On Tue, 22 Sep 2015, David Malcolm wrote:

> The drawback is that it could bloat the ad-hoc table.  Can the ad-hoc
> table ever get smaller, or does it only ever get inserted into?

It only ever grows.

> An idea I had is that we could stash short ranges directly into the 32 
> bits of location_t, by offsetting the per-column-bits somewhat.

It's certainly worth an experiment: let's say you restrict yourself to 
tokens less than 8 characters, you need an additional 3 bits (using one 
value, e.g. zero, as the escape value).  That leaves 20 bits for the line 
numbers (for the normal 8 bit columns), which might be enough for most 
single-file compilations.  For LTO compilation this often won't be enough.

> My plan is to investigate the impact these patches have on the time and 
> memory consumption of the compiler,

When you do so, make sure you're also measuring an LTO compilation with 
debug info of something big (firefox).  I know that we already had issues 
with the size of the linemap data in the past for these cases (probably 
when we added columns).


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