add Busmapping coinbase code

bus-mapping/src/evm/opcodes.rs

@@ -1,4 +1,5 @@
 //! Definition of each opcode of the EVM.
+mod coinbase;
 mod dup;
 pub mod ids;
 mod jump;
@@ -22,6 +23,7 @@ use ids::OpcodeId;
 use log::warn;
 
 use self::push::Push;
+use coinbase::Coinbase;
 use dup::Dup;
 use jump::Jump;
 use jumpdest::Jumpdest;
@@ -110,7 +112,7 @@ impl OpcodeId {
             // OpcodeId::RETURNDATACOPY => {},
             // OpcodeId::EXTCODEHASH => {},
             // OpcodeId::BLOCKHASH => {},
-            // OpcodeId::COINBASE => {},
+            OpcodeId::COINBASE => Coinbase::gen_associated_ops,
             // OpcodeId::TIMESTAMP => {},
             // OpcodeId::NUMBER => {},
             // OpcodeId::DIFFICULTY => {},

bus-mapping/src/evm/opcodes/coinbase.rs

@@ -0,0 +1,91 @@
+use super::Opcode;
+use crate::circuit_input_builder::CircuitInputStateRef;
+use crate::eth_types::GethExecStep;
+use crate::{operation::RW, Error};
+
+/// Placeholder structure used to implement [`Opcode`] trait over it
+/// corresponding to the [`OpcodeId::PC`](crate::evm::OpcodeId::PC) `OpcodeId`.
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct Coinbase;
+
+impl Opcode for Coinbase {
+    fn gen_associated_ops(
+        state: &mut CircuitInputStateRef,
+        steps: &[GethExecStep],
+    ) -> Result<(), Error> {
+        let step = &steps[0];
+        // Get value result from next step and do stack write
+        let value = steps[1].stack.last()?;
+        state.push_stack_op(
+            RW::WRITE,
+            step.stack.last_filled().map(|a| a - 1),
+            value,
+        );
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod coinbase_tests {
+    use super::*;
+    use crate::{
+        bytecode,
+        circuit_input_builder::{ExecStep, TransactionContext},
+        eth_types::ToWord,
+        evm::StackAddress,
+        mock,
+    };
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn coinbase_opcode_impl() -> Result<(), Error> {
+        let code = bytecode! {
+            #[start]
+            COINBASE
+            STOP
+        };
+
+        // Get the execution steps from the external tracer
+        let block =
+            mock::BlockData::new_single_tx_trace_code_at_start(&code).unwrap();
+
+        let mut builder = block.new_circuit_input_builder();
+        builder.handle_tx(&block.eth_tx, &block.geth_trace).unwrap();
+
+        let mut test_builder = block.new_circuit_input_builder();
+        let mut tx = test_builder.new_tx(&block.eth_tx).unwrap();
+        let mut tx_ctx = TransactionContext::new(&block.eth_tx);
+
+        // Generate step corresponding to COINBASE
+        let mut step = ExecStep::new(
+            &block.geth_trace.struct_logs[0],
+            0,
+            test_builder.block_ctx.rwc,
+            0,
+        );
+        let mut state_ref =
+            test_builder.state_ref(&mut tx, &mut tx_ctx, &mut step);
+
+        // Add the last Stack write
+        state_ref.push_stack_op(
+            RW::WRITE,
+            StackAddress::from(1024 - 1),
+            block.ctants.coinbase.to_word(),
+        );
+
+        tx.steps_mut().push(step);
+        test_builder.block.txs_mut().push(tx);
+
+        // Compare first step bus mapping instance
+        assert_eq!(
+            builder.block.txs()[0].steps()[0].bus_mapping_instance,
+            test_builder.block.txs()[0].steps()[0].bus_mapping_instance,
+        );
+
+        // Compare containers
+        assert_eq!(builder.block.container, test_builder.block.container);
+
+        Ok(())
+    }
+}