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 {

crates/llvm-context/src/polkavm/evm/context.rs

@@ -17,12 +17,12 @@ where
 
 /// Translates the `gas_price` instruction.
 pub fn gas_price<'ctx, D>(
-    _context: &mut Context<'ctx, D>,
+    context: &mut Context<'ctx, D>,
 ) -> anyhow::Result<inkwell::values::BasicValueEnum<'ctx>>
 where
     D: Dependency + Clone,
 {
-    todo!()
+    Ok(context.word_const(1).as_basic_value_enum())
 }
 
 /// Translates the `tx.origin` instruction.

crates/runtime-api/src/polkavm_imports.c

@@ -113,3 +113,5 @@ POLKAVM_IMPORT(void, return_data_size, uint32_t)
 POLKAVM_IMPORT(void, set_immutable_data, uint32_t, uint32_t);
 
 POLKAVM_IMPORT(void, value_transferred, uint32_t)
+
+POLKAVM_IMPORT(void, weight_to_fee, uint64_t, uint64_t, uint32_t);

crates/runtime-api/src/polkavm_imports.rs

@@ -64,9 +64,11 @@ pub static SET_IMMUTABLE_DATA: &str = "set_immutable_data";
 
 pub static VALUE_TRANSFERRED: &str = "value_transferred";
 
+pub static WEIGHT_TO_FEE: &str = "weight_to_fee";
+
 /// All imported runtime API symbols.
 /// Useful for configuring common attributes and linkage.
-pub static IMPORTS: [&str; 27] = [
+pub static IMPORTS: [&str; 28] = [
     SBRK,
     MEMORY_SIZE,
     ADDRESS,
@@ -94,6 +96,7 @@ pub static IMPORTS: [&str; 27] = [
     SET_IMMUTABLE_DATA,
     SET_STORAGE,
     VALUE_TRANSFERRED,
+    WEIGHT_TO_FEE,
 ];
 
 /// Creates a LLVM module from the [BITCODE].