New tests.

test/libsolidity/semanticTests/arithmetics/unchecked_div_by_zero.sol

@@ -0,0 +1,22 @@
+contract C {
+    function div(uint256 a, uint256 b) public returns (uint256) {
+        // Does not disable div by zero check
+        unchecked {
+            return a / b;
+        }
+    }
+
+    function mod(uint256 a, uint256 b) public returns (uint256) {
+        // Does not disable div by zero check
+        unchecked {
+            return a % b;
+        }
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// div(uint256,uint256): 7, 2 -> 3
+// div(uint256,uint256): 7, 0 -> FAILURE # throws #
+// mod(uint256,uint256): 7, 2 -> 1
+// mod(uint256,uint256): 7, 0 -> FAILURE # throws #