Implement the gasprice opcode (#127)

crates/integration/contracts/GasPrice.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8;
+
+/* runner.json
+{
+    "differential": false,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "GasPrice"
+                    }
+                }
+            }
+        },
+        {
+            "VerifyCall": {
+                "success": true
+            }
+        }
+    ]
+}
+*/
+
+contract GasPrice {
+    constructor() payable {
+        assert(tx.gasprice == 1);
+    }
+}

crates/integration/src/tests.rs

@@ -46,6 +46,7 @@ test_spec!(immutables, "Immutables", "Immutables.sol");
 test_spec!(transaction, "Transaction", "Transaction.sol");
 test_spec!(block_hash, "BlockHash", "BlockHash.sol");
 test_spec!(delegate, "Delegate", "Delegate.sol");
+test_spec!(gas_price, "GasPrice", "GasPrice.sol");
 
 fn instantiate(path: &str, contract: &str) -> Vec<SpecsAction> {
     vec![Instantiate {