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[ARM] Enable subreg liveness

Authored by dmgreen on Aug 17 2021, 6:10 AM.

Description

[ARM] Enable subreg liveness

This enables subreg liveness in the arm backend when MVE is present,
which allows the register allocator to detect when subregister are
alive/dead, compared to only acting on full registers. This can helps
produce better code on MVE with the way MQPR registers are made up of
SPR registers, but is especially helpful for MQQPR and MQQQQPR
registers, where there are very few "registers" available and being able
to split them up into subregs can help produce much better code.

Differential Revision: https://reviews.llvm.org/D107642

Details

Committed
dmgreenAug 17 2021, 6:10 AM
Differential Revision
D107642: [ARM] Enable subreg liveness
Parents
rG62e892fa2d4f: [ARM] Add MQQPR and MQQQQPR spill and reload pseudo instructions
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