chore: reuse unmodified step memory (#7385)

* chore: only record changed memory

* chore: only record changed memory

* chore: use returndata Bytes

* clippy

* clippy

crates/evm/core/src/debug.rs

@@ -1,3 +1,4 @@
+use crate::opcodes;
 use alloy_primitives::{Address, Bytes, U256};
 use revm::interpreter::OpCode;
 use revm_inspectors::tracing::types::CallKind;
@@ -168,11 +169,11 @@ pub struct DebugStep {
     /// Stack *prior* to running the associated opcode
     pub stack: Vec<U256>,
     /// Memory *prior* to running the associated opcode
-    pub memory: Vec<u8>,
+    pub memory: Bytes,
     /// Calldata *prior* to running the associated opcode
     pub calldata: Bytes,
     /// Returndata *prior* to running the associated opcode
-    pub returndata: Vec<u8>,
+    pub returndata: Bytes,
     /// Opcode to be executed
     pub instruction: Instruction,
     /// Optional bytes that are being pushed onto the stack
@@ -210,6 +211,11 @@ impl DebugStep {
             self.instruction.to_string()
         }
     }
+
+    /// Returns `true` if the opcode modifies memory.
+    pub fn opcode_modifies_memory(&self) -> bool {
+        self.instruction.opcode().and_then(OpCode::new).map_or(false, opcodes::modifies_memory)
+    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
@@ -249,3 +255,14 @@ impl Display for Instruction {
         }
     }
 }
+
+impl Instruction {
+    /// Returns the opcode of the instruction, if it is an opcode.
+    #[inline]
+    pub fn opcode(&self) -> Option<u8> {
+        match self {
+            Instruction::OpCode(op) => Some(*op),
+            _ => None,
+        }
+    }
+}

crates/evm/core/src/lib.rs

@@ -15,6 +15,7 @@ pub mod constants;
 pub mod debug;
 pub mod decode;
 pub mod fork;
+pub mod opcodes;
 pub mod opts;
 pub mod snapshot;
 pub mod utils;

crates/evm/core/src/opcodes.rs

@@ -0,0 +1,25 @@
+//! Opcode utils
+
+use revm::interpreter::OpCode;
+
+/// Returns true if the opcode modifies memory.
+/// <https://bluealloy.github.io/revm/crates/interpreter/memory.html#opcodes>
+/// <https://github.com/crytic/evm-opcodes>
+#[inline]
+pub const fn modifies_memory(opcode: OpCode) -> bool {
+    matches!(
+        opcode,
+        OpCode::EXTCODECOPY |
+            OpCode::MLOAD |
+            OpCode::MSTORE |
+            OpCode::MSTORE8 |
+            OpCode::MCOPY |
+            OpCode::CODECOPY |
+            OpCode::CALLDATACOPY |
+            OpCode::RETURNDATACOPY |
+            OpCode::CALL |
+            OpCode::CALLCODE |
+            OpCode::DELEGATECALL |
+            OpCode::STATICCALL
+    )
+}

crates/evm/evm/src/inspectors/debugger.rs

@@ -72,12 +72,28 @@ impl<DB: DatabaseExt> Inspector<DB> for Debugger {
             interp.gas.refunded() as u64,
         );
 
+        // if the previous opcode does __not__ modify memory, we can reuse the memory of
+        // that step
+        let memory = self.arena.arena[self.head]
+            .steps
+            .last()
+            .and_then(|step| {
+                if !step.opcode_modifies_memory() {
+                    // reuse the memory from the previous step, because its opcode did not modify
+                    // memory
+                    Some(step.memory.clone())
+                } else {
+                    None
+                }
+            })
+            .unwrap_or_else(|| interp.shared_memory.context_memory().to_vec().into());
+
         self.arena.arena[self.head].steps.push(DebugStep {
             pc,
             stack: interp.stack().data().clone(),
-            memory: interp.shared_memory.context_memory().to_vec(),
+            memory,
             calldata: interp.contract().input.clone(),
-            returndata: interp.return_data_buffer.to_vec(),
+            returndata: interp.return_data_buffer.clone(),
             instruction: Instruction::OpCode(op),
             push_bytes,
             total_gas_used,