[llvm] [VPlan] Move FOR splice cost into VPInstruction::FirstOrderRecurrenceSplice (PR #129645)

[Luke Lau via llvm-commits]

lukel97 wrote:

> > %arrayidx = getelementptr inbounds nuw i64, ptr %A, i64 %indvars
> > %0 = load i64, ptr %arrayidx, align 4
> > %add = add nsw i64 %for1, %0
> > %arrayidx2 = getelementptr inbounds nuw i64, ptr %B, i64 %indvars
> > store i64 %add, ptr %arrayidx2, align 4
> 
> I guess the issue might be due to load/store alignment. Try changing it to align 8 and try again.

Argh that's exactly it, I think I have align attribute blindness. Ignore my previous comments!

https://github.com/llvm/llvm-project/pull/129645