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From: "munroesj at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/104124] Poor optimization for vector splat DW with small
 consts
Date: Wed, 19 Jan 2022 17:51:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104124

Steven Munroe <munroesj at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |munroesj at gcc dot gnu.org

--- Comment #1 from Steven Munroe <munroesj at gcc dot gnu.org> ---
Created attachment 52236
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D52236&action=3Dedit
Attempts to load small int consts to vector DW via splat

Multiple attempt to convince GCC to load small integer (-16 - 15) constants=
 via
splat. Current GCC versions (9/10/11) convert vec_splats(<small const>) and
explicit vec_splat_s32/vec_unpackl sequences into to loads from .rodata. Th=
is
generates more instruction, takes more cycles, and causes register pressure
that results in unnecessary spill/reload and load-hit-store rejects.=