[llvm] [LoopUnroll] Allow unrolling of multi-exit loops with small trip count (PR #224325)

[Marek Sedláček via llvm-commits]

mark-sed wrote:

@fhahn Here are initial results from my weekend experiment, it was around 200 workloads that I ran and dumped the IR to collect stats. I still need to refine this and I'll post that later, but here are initial results:

Before:
Total loop-unroll.NumUnrolled: **4582**
Total loop-unroll.NumRuntimeUnrolled: **3180**
Total loop-vectorize.LoopsAnalyzed: 34118
Total loop-vectorize.LoopsVectorized: 10175

After:
Total loop-unroll.NumUnrolled: **6750**
Total loop-unroll.NumRuntimeUnrolled: **5313**
Total loop-vectorize.LoopsAnalyzed: 34284
Total loop-vectorize.LoopsVectorized: 10302

https://github.com/llvm/llvm-project/pull/224325