[Bug tree-optimization/61515] [4.9/5 Regression] Extremely long compile time for generated code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61515

--- Comment #20 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 33766
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33766&action=edit
non-working patch

Of course this still walks all SSA names (but only once per BB), so it isn't
really removing the quadraticness.

Moreover the patch (see attachment) I was testing fails to bootstrap on the
4.9 branch, seemingly miscompiling stage2 gcc (and crashing in building stage2
libgcc in swap_tree_comparison called from IVOPTs).

Eventually record_temporary_equivalences_from_stmts_at_dest depends on the
exact ordering of record_temporary_equivalence calls (I do the invaldiate ones
late).  Jeff?  As this is a regression from 4.9.0 appearing in 4.9.1 it's quite
bad that this is now still unfixed given we are about to release 4.9.2.

I'm out of here again ;)