Support solc v0.8.31 (#430)

- Support for solc v0.8.31.
- Support for the `clz` Yul builtin.

---------

Signed-off-by: xermicus <cyrill@parity.io>

crates/integration/contracts/CountLeadingZeros.sol

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.31;
+
+/* runner.json
+{
+    "differential": true,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "CountLeadingZeros"
+                    }
+                }
+            }
+        }
+    ]
+}
+*/
+
+/// The EIP-7939 test vectors:
+/// https://eips.ethereum.org/EIPS/eip-7939#test-cases
+contract CountLeadingZeros {
+    function clz(uint256 x) internal pure returns (uint256 r) {
+        assembly {
+            r := clz(x)
+        }
+    }
+
+    constructor() payable {
+        assert(
+            clz(0x000000000000000000000000000000000000000000000000000000000000000)
+                == 0x0000000000000000000000000000000000000000000000000000000000000100
+        );
+        assert(
+            clz(0x8000000000000000000000000000000000000000000000000000000000000000)
+                == 0x0000000000000000000000000000000000000000000000000000000000000000
+        );
+        assert(
+            clz(0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff)
+                == 0x0000000000000000000000000000000000000000000000000000000000000000
+        );
+        assert(
+            clz(0x4000000000000000000000000000000000000000000000000000000000000000)
+                == 0x0000000000000000000000000000000000000000000000000000000000000001
+        );
+        assert(
+            clz(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff)
+                == 0x0000000000000000000000000000000000000000000000000000000000000001
+        );
+        assert(
+            clz(0x0000000000000000000000000000000000000000000000000000000000000001)
+                == 0x00000000000000000000000000000000000000000000000000000000000000ff
+        );
+    }
+}

crates/integration/src/tests.rs

@@ -65,6 +65,7 @@ test_spec!(shift_arithmetic_right, "SAR", "SAR.sol");
 test_spec!(add_mod_mul_mod, "AddModMulModTester", "AddModMulMod.sol");
 test_spec!(memory_bounds, "MemoryBounds", "MemoryBounds.sol");
 test_spec!(selfdestruct, "Selfdestruct", "Selfdestruct.sol");
+test_spec!(clz, "CountLeadingZeros", "CountLeadingZeros.sol");
 
 fn instantiate(path: &str, contract: &str) -> Vec<SpecsAction> {
     vec![Instantiate {