[llvm] [LVI] Learn value ranges from ctpop/ctlz/cttz results (PR #121945)

[Stephen Senran Zhang via llvm-commits]

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@@ -1159,6 +1164,67 @@ getRangeViaSLT(CmpInst::Predicate Pred, APInt RHS,
   return std::nullopt;
 }
 
+static bool matchBitIntrinsic(Value *LHS, Value *Val, Intrinsic::ID &IID) {
+  auto *II = dyn_cast<IntrinsicInst>(LHS);
+  if (!II)
+    return false;
+  auto ID = II->getIntrinsicID();
+  switch (ID) {
+  case Intrinsic::ctpop:
+  case Intrinsic::ctlz:
+  case Intrinsic::cttz:
+    break;
+  default:
+    return false;
+  }
+  if (II->getArgOperand(0) != Val)
+    return false;
+  IID = ID;
+  return true;
+}
+
+/// Get value range for a "intrinsic(Val) Pred RHS" condition, where intrinsic
+/// can be one of ctpop, ctlz, and cttz.
+std::optional<ValueLatticeElement>
+LazyValueInfoImpl::getValueFromICmpBitIntrinsic(ICmpInst::Predicate Pred,
+                                                unsigned ValBitWidth,
+                                                Intrinsic::ID IID, Value *RHS,
+                                                Instruction *CtxI,
+                                                bool UseBlockValue) {
+  unsigned BitWidth = ValBitWidth;
+  auto Offset = APInt::getZero(BitWidth);
+
+  auto ResValLattice =
+      getValueFromSimpleICmpCondition(Pred, RHS, Offset, CtxI, UseBlockValue);
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zsrkmyn wrote:

Done

https://github.com/llvm/llvm-project/pull/121945