[Bug rtl-optimization/49936] [4.7 regression] IRA handles CANNOT_CHANGE_MODE_CLASS poorly, + spills to memory on 4.7

[sandra at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49936

--- Comment #1 from Sandra Loosemore <sandra at codesourcery dot com> 2011-08-01 19:44:34 UTC ---
Created attachment 24886
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24886
WIP patch to MIPS backend

Here is the WIP patch I referred to earlier.  This patch (which handles abs
only) produced pretty good code on 4.6 by adding MIPS-specific expansions of
abs with explicit register constraints, but didn't fix the memory spills on
4.7.  Since this is pretty complicated, I think it would be better to fix IRA
to deal better with CANNOT_CHANGE_MODE_CLASS in a target-inspecific way than
continue farther down this route.