[PATCH] D14332: [ARM] Combine CMOV into BFI where possible

[James Molloy via llvm-commits]

jmolloy created this revision.
jmolloy added reviewers: t.p.northover, mcrosier.
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Herald added subscribers: rengolin, aemerson.

If we have a CMOV, OR and AND combination such as:

  if (x & CN)
    y |= CM;

And:
  * CN is a single bit;
  * All bits covered by CM are known zero in y;

Then we can convert this to a sequence of BFI instructions. This will always be a win if CM is a single bit, will always be no worse than the TST & OR sequence if CM is two bits, and for thumb will be no worse if CM is three bits (due to the extra IT instruction).

Repository:
  rL LLVM

http://reviews.llvm.org/D14332

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  lib/Target/ARM/ARMISelLowering.h
  test/CodeGen/ARM/bfi.ll

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