[llvm] [VPlan] Constant-fold ActiveLaneMask intrinsics (PR #208852)

[Ramkumar Ramachandra via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --filter "active.lane.mask" --version 6
+; RUN: opt -mtriple=aarch64 -mcpu=neoverse-v1 -passes=loop-vectorize -force-vector-width="vscale x 4" -force-vector-interleave=1 -tail-folding-policy=prefer-fold-tail -disable-output -vplan-print-after=printFinalVPlan %s 2>&1 | FileCheck %s
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+; We never emit scalable active.lane.masks foldable to false.
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artagnon wrote:

Correct, see https://github.com/llvm/llvm-project/pull/208852/changes#r4121113650.

https://github.com/llvm/llvm-project/pull/208852