Re: Designs for better debug info in GCC

[Alexandre Oliva <aoliva@redhat.com>]

On Dec 20, 2007, Ian Lance Taylor <iant@google.com> wrote:

> Right, which will significantly increase debugging size as you add two
> more notes around many lines.

FWIW, I've just got powerpc64-linux-gnu to pass bootstrap-debug and
bootstrap4-debug/-g0 (i.e., all host and target libraries pass
compare-debug when compiled with -g0 and -g2
-fvar-tracking-assignments).  I did
bootstrap4-debug/-fno-var-tracking-assignments as well, for comparison
purposes.  Here are the total sizes:

1487400 target libs at -g0
2239140 target libs with -g2 -fno-var-tracking-assignments
2190176 target libs with -g2 -fvar-tracking-assignments

So, with the new infrastructure in place, debug info gets smaller.  I
haven't evaluated its quality yet (e.g., the compiler may be losing
track of where variables are too often).  Also, the compiler is still
missing the improved version of var-tracking to keep track of all
copies of user variable values, which is expected to grow debug info.
But at least at this point it doesn't seem like the approach is
hopeless.

-- 
Alexandre Oliva         http://www.lsd.ic.unicamp.br/~oliva/
FSF Latin America Board Member         http://www.fsfla.org/
Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}