[PATCH] D42574: [ARM] Lower lower saturate to 0 and lower saturate to -1 using bit-operations

[Marten Svanfeldt via Phabricator via llvm-commits]

thebolt created this revision.
Herald added subscribers: kristof.beyls, javed.absar, aemerson.

Expressions of the form x < 0 ? 0 :  x; and x < -1 ? -1 : x can be lowered using bit-operations instead of branching or conditional moves

In thumb-mode this results in a two-instruction sequence, a shift followed by a bic or or while in ARM/thumb2 mode that has flexible second operand the shift can be folded into a single bic/or instructions. In most cases this results in smaller code and possibly less branches, and in no case larger than before.


Repository:
  rL LLVM

https://reviews.llvm.org/D42574

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  test/CodeGen/ARM/atomic-op.ll
  test/CodeGen/ARM/sat-to-bitop.ll
  test/CodeGen/ARM/select.ll
  test/CodeGen/Thumb/select.ll

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