[Bug middle-end/54146] Very slow compile at -O1 (expand vars)

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54146

--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> 2012-07-31 22:16:58 UTC ---
Created attachment 27915
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27915
Speed up stack var conflict matric computation

The patch speeds up the conflict matrix computation in three ways:

1. Nested EXECUTE_IF_SET_IN_BITMAP is extremely inefficient. The same conflicts
result if one IORs the bitmaps.

2. Self-conflicts should not be recorded (this helps stack_var_conflict_p too).

3. The conflicts matrix can be stored in upper triangular form.


Debugging, bootstrapping, testing, and other activities involved in
contributing this formally are left as an exercise to the reader... ;-)