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

[David Sherwood via llvm-commits]

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@@ -1760,16 +1760,42 @@ 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;
+  bool HasSafeAccess =
+      TTI->supportsSpeculativeLoads()
+          ? isReadOnlyLoopWithSafeOrSpeculativeLoads(
+                TheLoop, PSE.getSE(), DT, AC, &NonDerefLoads, &Predicates)
+          : isDereferenceableReadOnlyLoop(TheLoop, PSE.getSE(), DT, AC,
+                                          &Predicates);
+  if (!HasSafeAccess) {
     reportVectorizationFailure(
         "Loop may fault",
         "Cannot vectorize potentially faulting early exit loop",
         "PotentiallyFaultingEarlyExitLoop", ORE, TheLoop);
     return false;
   }
+  // Speculative loads need to be unit-stride.
+  for (LoadInst *LI : NonDerefLoads) {
+    int Stride = isConsecutivePtr(LI->getType(), LI->getPointerOperand());
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david-arm wrote:

You can invoke `supportsSpeculativeLoads` by passing in the loaded memory type for each load.

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