[LLVMdev] PR21302: Vectorize only bottom-tested loops

[Michael Zolotukhin]

Thanks! Committed in r223170 and r223171.

Michael

> On Dec 2, 2014, at 2:57 PM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:
> 
> LGTM.
> 
> Thanks!
> 
> On 12/02/14, Michael Zolotukhin   wrote:
>> Hi,
>> 
>> This patch fixes the problem described in PR21302.
>> 
>> The issue is that currently vectorizer sometimes vectorizes loops that are not bottom-tested, i.e. in which each iteration starts from checking the termination condition. That causes an extra-iteration to be executed in vectorized version in some cases.
>> 
>> The patch consists of two parts:
>> 1) Update three existing tests, that contained loop in such forms. After the fix these loops aren’t vectorized any longer, so I applied loop-rotate+simplifycfg to them. This change is quite mechanical.
>> 2) The fix itself and a regression test.
>> 
>> 
>> 
>> 
>> 
>> Do they look ok?
>> 
>> Thanks,
>> Michael
>