RFR: 8302652: [SuperWord] Reduction should happen after loop, when possible [v4]

[Emanuel Peter]

On Wed, 10 May 2023 08:03:57 GMT, Pengfei Li <pli at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   small bugfix. And put TraceNewVector in VectorNode::trace_new_vector
>
> src/hotspot/share/opto/loopnode.cpp line 4636:
> 
>> 4634:     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
>> 4635:       IdealLoopTree* lpt = iter.current();
>> 4636:       if (lpt->_head->is_CountedLoop()) {
> 
> Using `lpt->is_counted()`? And how about adding one more condition of `lpt->is_innermost()` in this `if`? As all loops in the IdealLoopTree are iterated here but only reduction operations in innermost loops may be vectorized by current Superword, we don't need to run into your `move_unordered_reduction_out_of_loop()` function for further analysis if a loop is not innermost.

Thanks for the suggestion, I changed it :)

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PR Review Comment: https://git.openjdk.org/jdk/pull/13056#discussion_r1189781256