[PATCH PR82965/PR83991]Fix invalid profile count in vectorization peeling

[Bin Cheng <Bin dot Cheng at arm dot com>]

Hi,
This patch fixes invalid profile count information in vectorization peeling.
Current implementation is a bit confusing for me since it tries to compute
an overall probability based on scaling probability and change of estimated
niters.  This patch does it in two steps.  Firstly it does the scaling, then
it adjusts to new estimated niters by simply adjusting loop's latch count
information; scaling the loop's count information by the proportion
new_estimated_niters/old_estimate_niters.  Of course we have to adjust loop
latch's count information back after scaling.

Bootstrap and test on x86_64 and AArch64.  gcc.dg/vect/pr79347.c is fixed
for both PR82965 and PR83991.  Is this OK?

Thanks,
bin

2018-01-30  Bin Cheng  <bin.cheng@arm.com>

	PR tree-optimization/82965
	PR tree-optimization/83991
	* cfgloopmanip.c (scale_loop_profile): Further scale loop's profile
	information if the loop was predicted to iterate too many times.

Attachment: pr82965-20180130.txt
Description: pr82965-20180130.txt