implement the blockhash opcode (#114)

crates/integration/codesize.json

@@ -1,10 +1,10 @@
 {
-  "Baseline": 967,
-  "Computation": 4022,
-  "DivisionArithmetics": 31787,
-  "ERC20": 44233,
-  "Events": 1743,
-  "FibonacciIterative": 2927,
-  "Flipper": 3408,
-  "SHA1": 26009
+  "Baseline": 961,
+  "Computation": 4024,
+  "DivisionArithmetics": 31789,
+  "ERC20": 44214,
+  "Events": 1737,
+  "FibonacciIterative": 2929,
+  "Flipper": 3402,
+  "SHA1": 26003
 }

crates/integration/contracts/BlockHash.sol

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8;
+
+/* runner.json
+{
+    "differential": false,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "Context"
+                    }
+                },
+                "data": "4545454545454545454545454545454545454545454545454545454545454545"
+            }
+        }
+    ]
+}
+*/
+
+contract BlockHash {
+    constructor(bytes32 expected) payable {
+        assert(blockhash(0) == expected);
+        assert(blockhash(1) == 0);
+        assert(
+            blockhash(
+                0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+            ) == 0
+        );
+    }
+}

crates/integration/src/tests.rs

@@ -44,6 +44,7 @@ test_spec!(transfer, "Transfer", "Transfer.sol");
 test_spec!(return_data_oob, "ReturnDataOob", "ReturnDataOob.sol");
 test_spec!(immutables, "Immutables", "Immutables.sol");
 test_spec!(transaction, "Transaction", "Transaction.sol");
+test_spec!(block_hash, "BlockHash", "BlockHash.sol");
 
 fn instantiate(path: &str, contract: &str) -> Vec<SpecsAction> {
     vec![Instantiate {