------- Comment #13 from steven at gcc dot gnu dot org 2009-01-20 23:01 ------- Created an attachment (id=17155) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17155&action=view) Throttle PRE, hookize SMALL_REGISTER_CLASSES
This is the patch I have in my local tree (bootstrapped&tested on AMD64 multilib). It's rather brute-force, but it shows what I would do: There is a new function want_to_pre_p that you can feed an expression to decide whether to perform the redundancy elimination or not. For x86 normal PRE (i.e. not PPRE) I toyed, quite successfully, with the idea to make the transformation depend on the probability that a PRE-ed expression will result in spills. I have not investigated at all whether there is a difference for PPRE and PRE in the want_to_pre_p decision. Some of Joern's ideas, and more (or less) should be included in this want_to_pre_p function. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38785
