IIUC Vplan needs LLVM 20 to have a cost model which is fairly necessary to keep it from generating tons of gather/scatter instructions.

Build looks like it works better on llvm 20, e.g. see https://github.com/Zentrik/llvm_julia_tester/actions/runs/13470189047?pr=59 (though possibly because I'm only compiling with JULIA_CPU_TARGET="generic;sandybridge,-xsaveopt,clone_all;haswell,-rdrnd,base(1)" due to #55844)

Never mind, I screwed up enabling VPlan, rebuilding.

Looks like Linux builds at least on 20, seeing lots of assertions hit in tests but llvm/llvm-project#121518 should fix that.

That's already backported to v20 though: llvm/llvm-project#126718, no?

I would presume not to our branch though

Right, but it is now, I just rebased https://github.com/JuliaLang/llvm-project/commits/julia-release/20.x/ on latest release/20.x

The fun part is that as far as I understand it, loops still need a manual loopinfo.vectorize annotation. So this is just turning on the option for outer loop vectorization and we start hitting assertions.

Unfortunately, looks like this won't work in 20, llvm/llvm-project#128425, and Julia doesn't even build on head.