r242088 - /branches/ARM/sve-branch/gcc/tree-vec...

[rsandifo@gcc.gnu.org]

Author: rsandifo
Date: Fri Nov 11 16:57:33 2016
New Revision: 242088

URL: https://gcc.gnu.org/viewcvs?rev=242088&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.

Modified:
    branches/ARM/sve-branch/gcc/tree-vect-loop.c