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r242475 - in /trunk/gcc: ChangeLog tree-vect-lo...


Author: rsandifo
Date: Wed Nov 16 10:18:25 2016
New Revision: 242475

URL: https://gcc.gnu.org/viewcvs?rev=242475&root=gcc&view=rev
Log:
Fix nb_iterations_estimate calculation in tree-vect-loop.c

vect_transform_loop has to reduce three iteration counts by
the vectorisation factor: nb_iterations_upper_bound,
nb_iterations_likely_upper_bound and nb_iterations_estimate.
All three are latch execution counts rather than loop body
execution counts.  The calculations were taking that into
account for the first two, but not for nb_iterations_estimate.

This patch updates the way the calculations are done to fix
this and to add a bit more commentary about what is going on.

gcc/
2016-11-15  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* tree-vect-loop.c (vect_transform_loop): Protect the updates of
	all three iteration counts with an any_* test.  Use a single update
	for each count.  Fix the calculation of nb_iterations_estimate.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-vect-loop.c


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