Re: Value Range Propagation Pass Status

[Jeffrey A Law <law at cygnus dot com>]

  In message <200002050005.TAA25324@jwlab.FEITH.COM>you write:
  > > I doubt there's much benefit in running it twice.  I suspect we can get 9
  > 9%
  > > of the benefit by running it once, probably before loop.
  > 
  > Running a second time after loop occurred to me in order to handle
  > unnecessary condition jumps resulting from loop unrolling which I've
  > seen happen.  For example using -O2 -funroll-all-loops on a x86 platform
  > to compile:
It may be the case that we want to run a second pass after loop if we're
unrolled any loops.

I've been thinking about ways to restructure the main loop in toplev.c so
that each optimization sets/resets flags so that we can intelligently rerun
passes only when they're likely to really help (or selectively invalidate
information like the cfg, life info, etc).  But I haven't actually tried to
do this yet :-)

jeff