[llvm] [LV] Add initial legality checks for loops with unbound loads. (PR #152422)

[Luke Lau via llvm-commits]

================
@@ -1760,16 +1760,31 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
   assert(LatchBB->getUniquePredecessor() == SingleUncountableExitingBlock &&
          "Expected latch predecessor to be the early exiting block");
 
-  // TODO: Handle loops that may fault.
   Predicates.clear();
-  if (!isDereferenceableReadOnlyLoop(TheLoop, PSE.getSE(), DT, AC,
-                                     &Predicates)) {
+  SmallVector<LoadInst *, 4> NonDerefLoads;
+  if (!isLoopSafeWithLoadOnlyFaults(TheLoop, PSE.getSE(), DT, AC,
+                                    &NonDerefLoads, &Predicates)) {
     reportVectorizationFailure(
         "Loop may fault",
-        "Cannot vectorize potentially faulting early exit loop",
-        "PotentiallyFaultingEarlyExitLoop", ORE, TheLoop);
+        "Cannot vectorize early exit loop with non-load faults",
+        "EarlyExitLoopWithNonLoadFaults", ORE, TheLoop);
----------------
lukel97 wrote:

IIUC if we reach here it's because the loop isn't read only, not necessarily that the stores etc. don't fault?

```suggestion
        "Cannot vectorize non-read-only early exit loop",
        "NonReadOnlyEarlyExitLoop", ORE, TheLoop);
```

https://github.com/llvm/llvm-project/pull/152422