[PATCH] D67404: [ARM] LE support in ConstantIslands

[Sam Parker via Phabricator via llvm-commits]

samparker created this revision.
samparker added reviewers: dmgreen, t.p.northover, SjoerdMeijer, olista01.
Herald added a subscriber: kristof.beyls.

The low-overhead branch extension provides a loop-end 'LE' instruction that performs no decrement nor compare, it just jumps backwards. This patch modifies the constant islands pass to try to insert LE instructions in place of a Thumb2 conditional branch, instead of shrinking it. This only happens if a cmp can be converted to a cbn/z and used to exit the loop.


https://reviews.llvm.org/D67404

Files:
  lib/Target/ARM/ARMConstantIslandPass.cpp
  test/CodeGen/ARM/O3-pipeline.ll
  test/CodeGen/Thumb2/LowOverheadLoops/no-dec-cbnz.mir
  test/CodeGen/Thumb2/LowOverheadLoops/no-dec-reorder.mir
  test/CodeGen/Thumb2/LowOverheadLoops/no-dec.mir

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