http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55283
Bug #: 55283
Summary: EON performance regression at -O2 due to loop
unrolling changes
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: hubi...@gcc.gnu.org
EON regressed by about 20% at -O2 due to
2012-11-06 Jan Hubicka <j...@suse.cz>
* cfgloopanal.c (get_loop_hot_path): New function.
* tree-ssa-lop-ivcanon.c (struct loop_size): Add CONSTANT_IV,
NUM_NON_PURE_CALLS_ON_HOT_PATH, NUM_PURE_CALLS_ON_HOT_PATH,
NUM_BRANCHES_ON_HOT_PATH.
(tree_estimate_loop_size): Compute the new values.
(try_unroll_loop_completely): Disable unrolling of loops with only
calls or too many branches.
(tree_unroll_loops_completely): Deal also with outer loops of hot
loops.
* cfgloop.h (get_loop_hot_path): Declare.
* params.def (PARAM_MAX_PEEL_BRANCHES): New parameters.
* invoke.texi (max-peel-branches): Document.
This seems to be bad cost model on array accesses because we unroll only for
size at -O2
