[llvm] [VPlan] Handle VPWidenCastRecipe without underlying value in EVL transform (PR #120194)

[Florian Hahn via llvm-commits]

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+; RUN: opt -passes=loop-vectorize -force-tail-folding-style=data-with-evl -prefer-predicate-over-epilogue=predicate-dont-vectorize -mtriple=riscv64 -mattr=+v -S %s
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fhahn wrote:

this should check the output, not just checking that it doesn't crash

https://github.com/llvm/llvm-project/pull/120194