On Tue, Jul 14, 2015 at 1:33 PM, Ajit Kumar Agarwal
<ajit.kumar.agar...@xilinx.com> wrote:
> All:
>
> I am trying the place the following Analysis in the vectorizer of GCC that
> helps in improving the vectorizer to a great extent
> For the unit stride, zero stride and non stride accesses of memory that helps
> in vectorizer.
>
> For the Data Dependency graph, the topological sort is performed. The
> topological sorted Data Dependence graph the time
> Stamp for each node of the DDG is assigned based on the following Algorithm.
>
> For each node in Topological sorted order in DDG
> {
>
> Timestamp = 0;
> Timestamp(node) = Max(Timestamp, Timestamp of all predecessors) + 1;
>
> }
>
> Based on the above calculation of timestamp, the partition of DDG is formed.
> Each partition of DDG is having the nodes with the same
> Stamp. So nodes in each partition can be vectorized as they are independent
> nodes in the DDG. To enable the vectorization, the accesses
> based on contiguous access and non-Contagious access the sub partition is
> formed. The memory address of all the operands of each node
> in the partition formed above is sorted in increasing/decreasing order. Based
> on the sorted increasing/decreasing order of the memory
> address of each operands of each node in the partition the sub partition is
> performed based on the unit stride access, zero stride access
> and the accesses that require shuffling of operands through the vectorized
> instruction.
>
> The above analysis will help in performing Data Layout on the partitioned
> nodes of the DDG and based on Sub partition formed above and
> more vectorization opportunities is enabled for performing data Layout on non
> contiguous accesses and the sub partition With the contiguous
> access helps in vectorization.
>
> Thoughts?
As mentioned for the other DDG related idea we already have loop distribution.
It is not enabled by default because it lacks a good cost model. It's current
cost-model looks after data locality/reuse only. Adding a cost
modeling targeting
vectorization sounds interesting.
Richard.
> Thanks & Regards
> Ajit
