[llvm] [KnownBits] Make `avg{Ceil,Floor}S` and `{s,u}{add,sub}_sat` optimal (PR #110329)

[Simon Pilgrim via llvm-commits]

================
@@ -306,14 +306,14 @@ TEST(KnownBitsTest, BinaryExhaustive) {
         return KnownBits::add(Known1, Known2);
       },
       [](const APInt &N1, const APInt &N2) { return N1 + N2; },
-      /*CheckOptimality=*/false);
+      /*CheckOptimality=*/true);
   testBinaryOpExhaustive(
       "sub",
       [](const KnownBits &Known1, const KnownBits &Known2) {
         return KnownBits::sub(Known1, Known2);
       },
       [](const APInt &N1, const APInt &N2) { return N1 - N2; },
-      /*CheckOptimality=*/false);
+      /*CheckOptimality=*/true);
----------------
RKSimon wrote:

Is this related to the patch?

https://github.com/llvm/llvm-project/pull/110329