[PATCH] D154217: [AArch64] Use known zero bits when creating BIC

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
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If we know bits are already 0, we will not need to clear them again with a BIC. So we can use KnownBits to shrink the size of the constant in the creation BIC from And, potentially undoing the known-bits folds that happen during compilation.

BIC only has a single register operand for input and output, so has less scheduling freedom than a AND, but usually saves the materialization of a constant.


https://reviews.llvm.org/D154217

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/test/CodeGen/AArch64/neon-bitwise-instructions.ll
  llvm/test/CodeGen/AArch64/shiftregister-from-and.ll
  llvm/test/CodeGen/AArch64/vec_uaddo.ll

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