[llvm] [RISCV] Prefer VLS over VLA if costs are equal (PR #100564)

[Luke Lau via llvm-commits]

lukel97 wrote:

> Is the cost affected by Zvl*b?

Doesn't the vectorizer estimate the scalable VF costs based off of Zvl*b via getVScaleForTuning to begin with? This would only make a difference in a tie-breaker. For other cases today the vectorizer might still choose a fixed VF even if the runtime VLEN might be more profitable

https://github.com/llvm/llvm-project/pull/100564