[Bug bootstrap/34255] scope-blocks-on-a-diet patch diverges -g from non-g output code

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #1 from rguenth at gcc dot gnu dot org  2007-11-28 10:14 -------
Confirmed.  The mentioned patch has been applied to the trunk already.

> The patch not only causes -g divergence, it also accidentally drops subblocks
> that need to be kept around for the sake of generating debug information for
> them.

This is certainly bad and needs to be (is already) fixed.

> http://gcc.gnu.org/ml/gcc-patches/2007-07/msg01745.html regresses the property
> that code output with -g must be the same as that without -g.  make
> bootstrap-debug demonstrates that several files miscompare after this patch,
> and don't if the patch is reversed.

This causes memory-usage regressions for non-debug builds, for example for
tramp3d-v4 at -O2 -Dleafify=flatten which (peak) memory-usage grows from 807MB
to 1248MB.  (Worse if you also add -fopenmp, less worse if you drop
-Dleafify=flatten)

The following two patches

http://gcc.gnu.org/ml/gcc-patches/2007-11/msg00523.html
http://gcc.gnu.org/ml/gcc-patches/2007-11/msg00524.html

probably address the latter problem in a more efficient way.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-11-28 10:14:58
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34255