[PATCH] D90606: [llvm][AArch64] Check the sign bit of a sign extended value before sign extension.

[Peter Waller via Phabricator via llvm-commits]

peterwaller-arm added a comment.

Nit: I think the commit message could be improved such that the benefit is clear? Something referencing the fact you're modifying the behaviour of TBZ.

Suggestion: "Allow TB(N)Z to drop signext for sign bit tests"

With the body explaining why/circumstances this helps: "For example if the sign extension is only used in for TBZ, and the value is used elsewhere with a zero extension, this can eliminate a sign extension".



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Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:5799
+// Looks through \param Val to determine the bit that can be used to
+// check the sign of the value. It returs the unextended value and the
+// sign bit position.
----------------
sp. returns


Repository:
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  https://reviews.llvm.org/D90606/new/

https://reviews.llvm.org/D90606