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The SAD routines are somewhat notorious for having low trip counts on their loops. As a result poor vector setup can significantly reduce the benefits from autovectorization. Using masked loads and/or strided loads can help widen the vectorization factor. and improve performance. Improvements to tree-ssa-forwprop.cc can eliminate the various VIEW_CONVERT_EXPR statements, collapse permutations, simplify bit insertion/extraction, etc. The goal being to hand off nearly optimal code to the RTL phase of the compiler.
It is believed that some work on finding a way to encourage unrolling an outer loop to enable wider vectorization of an inner loop would help the SATD routines. Neither GCC nor LLVM do a good job at this.
The SATD routines may have a loop which is not currently vectorized. We need to perform variable expansion before vectorization to have any chance of vectorizing the first part of the SATD routines.
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Stakeholders/Partners
RISE:
Ventana: Robin Dapp
Ventana: Jeff Law
External:
Dependencies
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Updates
- Project reported as a priority for 1H2024
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