[llvm] [NFC] SimplifyCFG: Detect switch replacement earlier in `switchToLookup` (PR #155602)

[Nikita Popov via llvm-commits]

================
@@ -6677,9 +6677,18 @@ Value *SwitchLookupTable::buildLookup(Value *Index, IRBuilder<> &Builder,
     // Mask off.
     return Builder.CreateTrunc(DownShifted, BitMapElementTy, "switch.masked");
   }
-  case ArrayKind: {
-    Type *IndexTy = DL.getIndexType(Array->getType());
-    auto *ArrayTy = cast<ArrayType>(Array->getValueType());
+  case LookupTableKind: {
+    // Only build lookup table when we have a target that supports it or the
+    // attribute is notable.
----------------
nikic wrote:

"or the attribute is notable"? What does that mean?

https://github.com/llvm/llvm-project/pull/155602