[PATCH] D104659: [ARM] Limit v6m unrolling with multiple live outs

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: SjoerdMeijer, samtebbs, NickGuy.
Herald added subscribers: danielkiss, zzheng, hiraditya, kristof.beyls.
dmgreen requested review of this revision.
Herald added a project: LLVM.

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 puts a limit on unroll count for loops with multiple live out values, as measured from the LCSSA phi nodes.


https://reviews.llvm.org/D104659

Files:
  llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
  llvm/test/Transforms/LoopUnroll/ARM/v6munroll.ll

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