[llvm] [VPlan] Add VPExpressionRecipe, replacing extended reduction recipes. (PR #144281)

[Florian Hahn via llvm-commits]

fhahn wrote:

> Got warning
> 
> ```
> llvm-project/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp: In member function ‘virtual llvm::InstructionCost llvm::VPExpressionRecipe::computeCost(llvm::ElementCount, llvm::VPCostContext&) const’:
> llvm-project/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp:2667:1: warning: control reaches end of non-void function [-Wreturn-type]
>  }
>  ^
> ```

Looks like @RKSimon fixed that in 651c5208f8597f1f80349f6208e69bf9ea1c2862. Seems like some clang-based compilers don't surface that warning

https://github.com/llvm/llvm-project/pull/144281