[llvm] Add ConstantRangeList::unionWith() and ::intersectWith() (PR #96547)

[Arthur Eubanks via llvm-commits]

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@@ -81,6 +81,86 @@ void ConstantRangeList::insert(const ConstantRange &NewRange) {
   }
 }
 
+ConstantRangeList
+ConstantRangeList::unionWith(const ConstantRangeList &CRL) const {
+  assert(getBitWidth() == CRL.getBitWidth() &&
+         "ConstantRangeList types don't agree!");
+  // Handle common cases.
+  if (empty())
+    return CRL;
+  if (CRL.empty())
+    return *this;
+
+  ConstantRangeList Result;
+  size_t i = 0, j = 0;
+  ConstantRange PreviousRange(getBitWidth(), false);
+  if (Ranges[i].getLower().slt(CRL.Ranges[j].getLower())) {
+    PreviousRange = Ranges[i++];
+  } else {
+    PreviousRange = CRL.Ranges[j++];
+  }
+  auto UnionAndUpdateRange = [&PreviousRange,
+                              &Result](const ConstantRange &CR) {
+    assert(!CR.isSignWrappedSet() && "Upper wrapped ranges are not supported");
----------------
aeubanks wrote:

these asserts should probably go into wherever we're adding a ConstantRange to a ConstantRangeList, rather than sprinkled throughout various other methods. then we can assume that this invariant holds for existing ConstantRangeLists and don't need extra asserts

https://github.com/llvm/llvm-project/pull/96547