This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] Fix PR46556 (poor address generation)
On Thu, 6 Oct 2011, Jeff Law wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 10/06/11 04:13, Richard Guenther wrote:
>
> >
> > People have already commented on pieces, so I'm looking only at the
> > tree-ssa-reassoc.c pieces (did you consider piggy-backing on IVOPTs
> > instead? The idea is to expose additional CSE opportunities,
> > right? So it's sort-of a strength-reduction optimization on scalar
> > code (classically strength reduction in loops transforms for (i) {
> > z = i*x; } to z = 0; for (i) { z += x }). That might be worth in
> > general, even for non-address cases. So - if you rename that thing
> > to tree-ssa-strength-reduce.c you can get away without
> > piggy-backing on anything ;) If you structure it to detect a
> > strength reduction opportunity (thus, you'd need to match
> > two/multiple of the patterns at the same time) that would be a
> > bonus ... generalizing it a little bit would be another.
> There's a variety of literature that uses PRE to detect and optimize
> straightline code strength reduction. I poked at it at one time (RTL
> gcse framework) and it looked reasonably promising. Never pushed it
> all the way through.
I poked at it in the tree PRE framework at some point but never
pushed it through either. At least it didn't feel like it "fits" PRE
(and PRE should also be able to handle the loop case).
Richard.