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[GOOGLE] don't overwrite precomputed loop bound in AutoFDO
- From: Dehao Chen <dehao at google dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: David Li <davidxl at google dot com>, Cong Hou <congh at google dot com>
- Date: Fri, 17 Jan 2014 09:08:00 -0800
- Subject: [GOOGLE] don't overwrite precomputed loop bound in AutoFDO
- Authentication-results: sourceware.org; auth=none
If a loop is cunrolled/vectorized, the AutoFDO computed trip count
will be very small. This patch disallows overwritting of precomputed
loop bound in AutoFDO mode.
Bootstrapped and passed regression test. Performance test on-going.
OK for Google branches?
Thanks,
Dehao
Index: tree-ssa-loop-niter.c
===================================================================
--- tree-ssa-loop-niter.c (revision 206674)
+++ tree-ssa-loop-niter.c (working copy)
@@ -2520,7 +2520,8 @@ record_niter_bound (struct loop *loop, double_int
}
if (realistic
&& (!loop->any_estimate
- || i_bound.ult (loop->nb_iterations_estimate)))
+ || (!flag_auto_profile &&
+ i_bound.ult (loop->nb_iterations_estimate))))
{
loop->any_estimate = true;
loop->nb_iterations_estimate = i_bound;