On Mon, Dec 12, 2011 at 6:53 PM, Sandra Loosemore <san...@codesourcery.com> wrote: > The test case in the attached patch gets stuck in an infinite loop in > find_comparison_args in CSE when compiled for MIPS at -O2. This bug has > been present at least as far back as GCC 4.5 and probably much earlier than > that. > > The problem is that the inner loop over equivalences in the hash table is > finding something that rewrites to exactly the same expression that we've > already got in the outer loop, and there is no test for circular rewrites. > > This patch fixes the specific problem in the test case by skipping over > equivalences that would rewrite to exactly the same expression as on the > current iteration. But, it's not clear that there can't also be cycles of > length > 1. I don't see much point in getting fancy here (I assume that if > this were a common problem it would have been reported and fixed long before > now) so I just added a simple limit on the number of iterations to be sure > the outer loop always terminates. > > I regression-tested this in a GCC 4.5-based build for mips-linux-gnu and > also did a full bootstrap and regression test for i686-pc-linux-gnu on > mainline head. OK to check in on mainline?
This is http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50380 . Thanks, Andrew Pinski
