[Bug tree-optimization/69347] [6 regression] excessive compile time with -O2

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69347

--- Comment #12 from Jeffrey A. Law <law at redhat dot com> ---
And in fact, we purposefully raised the maximum amount of memory that we allow
GCSE to allocate (precisely for this kind of function).  This testcase now
comes in under that maximum limit and thus we GCSE this function.

If I use the same limits, then we're looking at a total of 17.56 seconds for
gcc-5 vs 19.08 for the trunk.  Roughly 2/3s of that slowdown is DOM.