[llvm] [LoopVectorize] Add support for vectorisation of more early exit loops (PR #88385)

[Graham Hunter via llvm-commits]

================
@@ -2616,13 +2656,21 @@ bool LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
   // other reads in this loop then is it safe to vectorize.
   if (NumReadWrites == 1 && NumReads == 0) {
     LLVM_DEBUG(dbgs() << "LAA: Found a write-only loop!\n");
-    return true;
+    if (!UncountableExitingBlocks.size())
----------------
huntergr-arm wrote:

```suggestion
    if (UncountableExitingBlocks.empty())
```

https://github.com/llvm/llvm-project/pull/88385