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

[Ramkumar Ramachandra via llvm-commits]

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@@ -185,9 +199,14 @@ KnownBits ValueEvolution::computeInstr(const Instruction *I) {
   // Compute the KnownBits for a Select(Cmp()), forcing it to take the branch
   // that is predicated on the (least|most)-significant-bit check.
   CmpPredicate Pred;
-  Value *L, *R, *TV, *FV;
-  if (match(I, m_Select(m_ICmp(Pred, m_Value(L), m_Value(R)), m_Value(TV),
-                        m_Value(FV)))) {
+  Value *L, *R;
+  Instruction *TV, *FV;
+  if (match(I, m_Select(m_ICmp(Pred, m_Value(L), m_Value(R)), m_Instruction(TV),
+                        m_Instruction(FV)))) {
+    Visited.insert(cast<Instruction>(I->getOperand(0)));
+    Visited.insert(TV);
+    Visited.insert(FV);
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artagnon wrote:

Think about it: what does eliding the significant-bit check effectively do? It means that none of the significant bits are 1, or that we started with a 0 crc (or xor crc data), resulting in a remainder of 0.

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