On 08/01/2016 03:09 AM, Ilya Enkovich wrote:
2016-07-26 18:38 GMT+03:00 Ilya Enkovich <enkovich....@gmail.com>:
2016-07-26 18:26 GMT+03:00 Jeff Law <l...@redhat.com>:
On 07/26/2016 03:57 AM, Ilya Enkovich wrote:
Ilya, what's the fundamental reason why we need to run
if-conversion again? Yes, I know you want to if-convert the
epilogue, but why?
What are the consequences of not doing if-conversion on the
epilogue? Presumably we miss a vectorization opportunity on the
tail. But that may be a reasonable limitation to allow the
existing work to move forward while you go back and revamp things a
little.
If we have some control-flow in a loop then we have to if-convert it
for vectorizer. We need to preserve both versions: if-converted one
for vectorizer and the original one to be used if vectorization
fails. For epilogues we have similar situation and need two
versions. I do it by running if-conversion on a copy of original
loop. Note that it doesn't run full if-conversion pass. If-conversion
is called for epilogue loop only.
Right. So what I think Richi wants you to try is to use the if-converted
loop to construct the if-converted epilogue. It seems conceptually simple
and low cost -- the question is on the implementation side. I have no clue
how painful that would be.
Probably another part of if-conversion may be re-used to build required
epilogue. I'll have a look.
Hi,
Yuri will continue my work from this point.
Understood. I'm actually got some comments on #5 and Yuri is already on
the CC list for that draft message.
Jeff
