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[AArch64] Add a special case for shifting by (BitWidth - 1) - X
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Authored by foad on Apr 2 2020, 9:15 AM.

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t.p.northover

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foad created this revision.Apr 2 2020, 9:15 AM

Commit the new tests against trunk and then rebase to show the codegen diffs

foad updated this revision to Diff 264445.May 16 2020, 9:12 AM

Rebase after precommitting tests.

What happens if the shift amount has more than one use?

llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
2794

Please use mvn to NOT a register. (This doesn't affect performance, but it's more readable.)