[llvm] [LV]Set tailfolding styles before computing feasible max VF. (PR #91403)

[via llvm-commits]

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@@ -4229,9 +4248,20 @@ LoopVectorizationCostModel::getMaxLegalScalableVF(unsigned MaxSafeElements) {
     reportVectorizationInfo("Scalable vectorization is not supported "
                             "for all element types found in this loop.",
                             "ScalableVFUnfeasible", ORE, TheLoop);
-    return ElementCount::getScalable(0);
+    return false;
   }
 
+  IsScalableVectorizationAllowed = true;
+  return true;
+}
+
+ElementCount
+LoopVectorizationCostModel::getMaxLegalScalableVF(unsigned MaxSafeElements) {
+  if (!isScalableVectorizationAllowed())
+    return ElementCount::getScalable(0);
+
+  auto MaxScalableVF = ElementCount::getScalable(
+      std::numeric_limits<ElementCount::ScalarTy>::max());
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ayalz wrote:

independent of this patch - this potentially overrides `MaxSafeElements` - worth some assert?

The report below refers to getScalable(MaxSafeElements / *MaxVScale) returning false, rather than getMaxVScale() returning false?

https://github.com/llvm/llvm-project/pull/91403