[Bug tree-optimization/41026] invariant address load inside loop with -Os.

[rahul at icerasemi dot com]

------- Comment #4 from rahul at icerasemi dot com  2009-08-13 15:46 -------
Confirmed. Introducing loop header copy for Os, resolves the problem.
On our port, this not only helps move the invariant load outside the loop, but
also correctly uses an auto-increment address mode via the AutoInc patches we
use. Other examples also confirm that the header copying enables more induction
variables to be identified and hence post-increment opportunities.

Does better loop analysis and hence potential for further optimizations
outweigh the cost of copying the loop header? It would be ideal to relax the
loop header copy predicate for Os and select an appropriate threshold,
currently set at 20 insn, a lower value to start with perhaps.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41026