------- Comment #14 from dberlin at gcc dot gnu dot org 2006-07-17 13:34 ------- Subject: Re: [4.0/4.1/4.2 Regression] Tree loop optimizer does worse job than RTL loop optimizer
rakdver at gcc dot gnu dot org wrote: > ------- Comment #13 from rakdver at gcc dot gnu dot org 2006-07-17 11:54 > ------- > (In reply to comment #12) >> The test case in comment #11 looks like a classic store motion opportunity to >> me. GCC 3.3 performs the store motion, GCC 4.2 r115467 does not. >> >> Zdenek, I thought tree-ssa-lim should be able to do store motion in loops? > > Yes, however again, the alias analysis does not tell it that a[0] does not > alias a[1]; once that is fixed, tree-ssa-lim should work just fine. This is because it's an incoming parameter, and as a result, this doesn't look at all like an array access, but just a random pointer access. I have no plans to make the alias analysis algorithm reconstruct array indexes from random pointer arithmetic. --Dan -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20643
