[PATCH] D27130: [AArch64] Fix useful bits detection for BFM instructions

[silviu.baranga@arm.com via Phabricator via llvm-commits]

sbaranga created this revision.
sbaranga added reviewers: t.p.northover, jmolloy.
sbaranga added a subscriber: llvm-commits.
Herald added subscribers: rengolin, aemerson.

When computing useful bits for a BFM instruction, we need
to take into consideration the case where both operands
of the BFM are equal and provide data that we need to track.

Not doing this can cause us to miss useful bits.

      

Fixes PR31138 (https://llvm.org/bugs/show_bug.cgi?id=31138)


https://reviews.llvm.org/D27130

Files:
  lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
  test/CodeGen/AArch64/arm64-bitfield-extract.ll

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