C compile time

[Robert Dewar]

> It would be better to improve GDB than to dumb down gcc's optimizations.
> Also work on merging things like var-tracking and dwarf2 location list
> support from the rtlopt-branch/cfg-branch for gcc, which helps immensely
> with optimized debugging.

Yes, but you still get transformations in the optimized code that cannot
be followed by the debugger in a clearly inteligent way.

I am not talking about dumbing down -O here, but rather in practice making
-O0 better.

In our world at least, people use -O0 primarily because they can
't debug at higher levels. Yes, it would be nice if this is fixed,
but it would also be nice if there was a debuggable level which did
not generate so much junk.

In comparison with other compilers, the performance in unoptimized, clearly
debuggable mode of gcc is rather poor, even if the -O2 code compares
favorably.