[llvm] [InstSimplify] Generalize simplification of icmps with monotonic operands (PR #69471)

[via llvm-commits]

================
@@ -3103,6 +3103,54 @@ static Value *simplifyICmpWithConstant(CmpInst::Predicate Pred, Value *LHS,
   return nullptr;
 }
 
+/// Get values V_i such that V uge V_i (Greater) or V ule V_i (!Greater).
+static void getUnsignedMonotonicValues(SmallPtrSetImpl<Value *> &Res, Value *V,
+                                       bool Greater, unsigned Depth = 0) {
+  if (!Res.insert(V).second)
+    return;
+
+  // Can be increased if useful.
+  if (++Depth > 1)
+    return;
+
+  Value *X, *Y;
+  if (Greater) {
+    if (match(V, m_Or(m_Value(X), m_Value(Y))) ||
+        match(V, m_Intrinsic<Intrinsic::uadd_sat>(m_Value(X), m_Value(Y)))) {
+      getUnsignedMonotonicValues(Res, X, Greater, Depth);
+      getUnsignedMonotonicValues(Res, Y, Greater, Depth);
+    }
+  } else {
+    if (match(V, m_And(m_Value(X), m_Value(Y)))) {
+      getUnsignedMonotonicValues(Res, X, Greater, Depth);
+      getUnsignedMonotonicValues(Res, Y, Greater, Depth);
+    } else if (match(V, m_URem(m_Value(X), m_Value())) ||
+               match(V, m_UDiv(m_Value(X), m_Value())) ||
+               match(V, m_LShr(m_Value(X), m_Value())) ||
+               match(V, m_Intrinsic<Intrinsic::usub_sat>(m_Value(X)))) {
+      getUnsignedMonotonicValues(Res, X, Greater, Depth);
----------------
goldsteinn wrote:

Don't need complete coverage here, but can you add TODO for some additional freebies (min/max/add+nuw/sub+nuw/mul+nuw/shl+nuw/ashr+signbit/etc...)

https://github.com/llvm/llvm-project/pull/69471