Adjust inner loop cost scaling

This makes use of the estimated number of iterations of the inner loop
to limit --param vect-inner-loop-cost-factor scaling.  It also reduces
the maximum value of vect-inner-loop-cost-factor to 10000 making it
less likely to cause overflow of costs.

2021-08-23  Richard Biener  <rguenther@suse.de>

	* doc/invoke.texi (vect-inner-loop-cost-factor): Adjust.
	* params.opt (--param vect-inner-loop-cost-factor): Adjust
	maximum value.
	* tree-vect-loop.c (vect_analyze_loop_form): Initialize
	inner_loop_cost_factor to the minimum of the estimated number
	of iterations of the inner loop and vect-inner-loop-cost-factor.

1 files changed, 4 insertions, 3 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index c057cc1..a9d56fe 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -14386,9 +14386,10 @@ The parameter only has an effect on targets that support partial
 vector loads and stores.
 
 @item vect-inner-loop-cost-factor
-The factor which the loop vectorizer applies to the cost of statements
-in an inner loop relative to the loop being vectorized.  The default
-value is 50.
+The maximum factor which the loop vectorizer applies to the cost of statements
+in an inner loop relative to the loop being vectorized.  The factor applied
+is the maximum of the estimated number of iterations of the inner loop and
+this parameter.  The default value of this parameter is 50.
 
 @item avoid-fma-max-bits
 Maximum number of bits for which we avoid creating FMAs.