[PATCH] D21686: Use SystemZ NILL instruction instead of NILF where possible

[Elliot Colp via llvm-commits]

colpell created this revision.
colpell added a reviewer: uweigand.
colpell added a subscriber: llvm-commits.

SystemZ shift instructions only use the last 6 bits of the shift amount. When the result of an AND operation is used as a shift amount, this means that we can use the NILL instruction (which operates on the last 16 bits) rather than NILF (which operates on the last 32 bits) for a 16-bit savings in instruction size.

http://reviews.llvm.org/D21686

Files:
  lib/Target/SystemZ/SystemZInstrInfo.td
  test/CodeGen/SystemZ/shift-11.ll

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