[PATCH] D26851: [SelectionDAG] ComputeNumSignBits of TRUNCATE operations

[Simon Pilgrim via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: qcolombet, eli.friedman, spatel, andreadb.
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Add basic ComputeNumSignBits support for TRUNCATE ops for cases where the source's number of sign bits overlaps with the truncated size.

Improves X86 SIGN_EXTEND_IN_REG vector cases which were needlessly sign extending boolean vector results.


Repository:
  rL LLVM

https://reviews.llvm.org/D26851

Files:
  lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  test/CodeGen/X86/avx512-mask-op.ll
  test/CodeGen/X86/psubus.ll

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