An issue for the SC: horrible documentation quality of GCC

[Richard Henderson]

On Fri, May 09, 2003 at 12:13:34PM -0400, Richard Kenner wrote:
> Indeed now that I see that message, I remember it.  But it doesn't answer the
> question I have: why is it appropriate to have *two* constant propagation
> routines within a basic block where only one (the one in cse.c) knows how to
> properly apply cost functions ...

Because cse.c is too slow.  It cannot be used for code cleanup
within another pass.  Compilation time being high on everyone's
minds, I think this is an exceedingly good reason to have two
passes.

As for examining or ignoring cost functions, Jan's patch seems
to have been a win on the major platforms.  Of course, they're
all fairly trivial when it comes to costs of constants that can
be recognized within instructions.


r~