llvm dev - Dec 2014 - [LLVMdev] PR21302: Vectorize only bottom-tested loops

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

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
>