Switch the inline hint to EIGEN_ALWAYS_INLINE for a few functions

Yu Yourequested to merge
youyu3/eigen:always-inline into master

Description

Switch the inline hint to EIGEN_ALWAYS_INLINE for a few functions This leads to performance gains in a few btl benchmarks with medium/small problem sizes for Clang and NVHPC. See #2993 (closed) for details and benchmarking results

Reference issue

Fixes #2993 (closed).

Additional information

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