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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.
jeff
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