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[ARM] Limit v6m unrolling with multiple live outs

Authored by dmgreen on Jun 23 2021, 8:36 AM.

Description

[ARM] Limit v6m unrolling with multiple live outs

v6m cores only have a limited number of registers available. Unrolling
can mean we spend more on stack spills and reloads than we save from the
unrolling. This patch adds an extra heuristic to put a limit on the
unroll count for loops with multiple live out values, as measured from
the LCSSA phi nodes.

Differential Revision: https://reviews.llvm.org/D104659

Details

Committed
dmgreenJun 23 2021, 8:36 AM
Differential Revision
D104659: [ARM] Limit v6m unrolling with multiple live outs
Parents
rGad0085d3381a: [InstCombine] Eliminate casts to optimize ctlz operation
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