[llvm] [LoopVectorize] Generate wide active lane masks (PR #147535)

[David Sherwood via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S --passes="default<O3>" -scalable-vectorization=off -prefer-predicate-over-epilogue=predicate-dont-vectorize -enable-wide-lane-mask \
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david-arm wrote:

I was trying to understand why the extractelements for the fixed-width masks were different from the scalable masks and then I realised it's because instcombine (or something else) has optimised the extracts differently. Can you regenerate the tests with just `-passes=loop-vectorize` please? I realise the output won't look so neat, but it does avoid this sort of inconsistency.

Also, looks like there is potentially a missing instcombine somewhere?

https://github.com/llvm/llvm-project/pull/147535