[llvm] [HashRecognize] Track visited in ValueEvolution (PR #147812)

[Piotr Fusik via llvm-commits]

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@@ -634,6 +649,19 @@ HashRecognize::recognizeCRC() const {
     return VE.getError();
   KnownBits ResultBits = VE.KnownPhis.at(ConditionalRecurrence.Phi);
 
+  // There must be exactly four unvisited instructions, corresponding to the
+  // IndVar PHI:
+  //   IndVar
+  //   Latch->getTerminator()
+  //   L.getLatchCmpInst(),
+  //   IndVar->getIncomingValueForBlock(Latch))
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pfusik wrote:

Can we instead insert these into visited instead of having a magic "4" in the code and this listing in a comment?

https://github.com/llvm/llvm-project/pull/147812