perf: use ArrayVec for collecting push bytes

Cargo.toml

@@ -186,6 +186,7 @@ alloy-rlp = "0.3.3"
 solang-parser = "=0.3.3"
 
 ## misc
+arrayvec = "0.7"
 base64 = "0.22"
 chrono = { version = "0.4", default-features = false, features = ["clock", "std"] }
 color-eyre = "0.6"

crates/evm/core/Cargo.toml

@@ -37,6 +37,7 @@ revm = { workspace = true, default-features = false, features = [
 ] }
 revm-inspectors.workspace = true
 
+arrayvec.workspace = true
 auto_impl = "1"
 derive_more.workspace = true
 eyre = "0.6"

crates/evm/core/src/debug.rs

@@ -1,5 +1,6 @@
 use crate::opcodes;
 use alloy_primitives::{Address, Bytes, U256};
+use arrayvec::ArrayVec;
 use revm::interpreter::OpCode;
 use revm_inspectors::tracing::types::CallKind;
 use serde::{Deserialize, Serialize};
@@ -176,8 +177,10 @@ pub struct DebugStep {
     pub returndata: Bytes,
     /// Opcode to be executed
     pub instruction: Instruction,
-    /// Optional bytes that are being pushed onto the stack
-    pub push_bytes: Option<Vec<u8>>,
+    /// Optional bytes that are being pushed onto the stack.
+    /// Empty if the opcode is not a push or PUSH0.
+    #[serde(serialize_with = "hex::serialize", deserialize_with = "deserialize_arrayvec_hex")]
+    pub push_bytes: ArrayVec<u8, 32>,
     /// The program counter at this step.
     ///
     /// Note: To map this step onto source code using a source map, you must convert the program
@@ -195,7 +198,7 @@ impl Default for DebugStep {
             calldata: Default::default(),
             returndata: Default::default(),
             instruction: Instruction::OpCode(revm::interpreter::opcode::INVALID),
-            push_bytes: None,
+            push_bytes: Default::default(),
             pc: 0,
             total_gas_used: 0,
         }
@@ -205,8 +208,8 @@ impl Default for DebugStep {
 impl DebugStep {
     /// Pretty print the step's opcode
     pub fn pretty_opcode(&self) -> String {
-        if let Some(push_bytes) = &self.push_bytes {
-            format!("{}(0x{})", self.instruction, hex::encode(push_bytes))
+        if !self.push_bytes.is_empty() {
+            format!("{}(0x{})", self.instruction, hex::encode(&self.push_bytes))
         } else {
             self.instruction.to_string()
         }
@@ -266,3 +269,12 @@ impl Instruction {
         }
     }
 }
+
+fn deserialize_arrayvec_hex<'de, D: serde::Deserializer<'de>>(
+    deserializer: D,
+) -> Result<ArrayVec<u8, 32>, D::Error> {
+    let bytes: Vec<u8> = hex::deserialize(deserializer)?;
+    let mut array = ArrayVec::new();
+    array.try_extend_from_slice(&bytes).map_err(serde::de::Error::custom)?;
+    Ok(array)
+}

crates/evm/evm/Cargo.toml

@@ -38,6 +38,7 @@ revm-inspectors.workspace = true
 
 itertools.workspace = true
 
+arrayvec.workspace = true
 eyre = "0.6"
 hex.workspace = true
 parking_lot = "0.12"

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

@@ -1,4 +1,5 @@
 use alloy_primitives::Address;
+use arrayvec::ArrayVec;
 use foundry_common::{ErrorExt, SELECTOR_LEN};
 use foundry_evm_core::{
     backend::DatabaseExt,
@@ -56,36 +57,29 @@ impl<DB: DatabaseExt> Inspector<DB> for Debugger {
         let opcode_info = &opcode_infos[op as usize];
 
         // Extract the push bytes
-        let push_size = if opcode_info.is_push() { (op - opcode::PUSH1 + 1) as usize } else { 0 };
-        let push_bytes = match push_size {
-            0 => None,
-            n => {
-                let start = pc + 1;
-                let end = start + n;
-                Some(interp.contract.bytecode.bytecode()[start..end].to_vec())
-            }
-        };
+        let push_size = if opcode_info.is_push() { (op - opcode::PUSH0) as usize } else { 0 };
+        let push_bytes = (push_size > 0).then(|| {
+            let start = pc + 1;
+            let end = start + push_size;
+            let slice = &interp.contract.bytecode.bytecode()[start..end];
+            assert!(slice.len() <= 32);
+            let mut array = ArrayVec::new();
+            array.try_extend_from_slice(slice).unwrap();
+            array
+        });
 
         let total_gas_used = gas_used(
             ecx.spec_id(),
             interp.gas.limit().saturating_sub(interp.gas.remaining()),
             interp.gas.refunded() as u64,
         );
 
-        // if the previous opcode does __not__ modify memory, we can reuse the memory of
-        // that step
+        // Reuse the memory from the previous step if the previous opcode did not modify it.
         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
-                }
-            })
+            .filter(|step| !step.opcode_modifies_memory())
+            .map(|step| step.memory.clone())
             .unwrap_or_else(|| interp.shared_memory.context_memory().to_vec().into());
 
         self.arena.arena[self.head].steps.push(DebugStep {
@@ -95,7 +89,7 @@ impl<DB: DatabaseExt> Inspector<DB> for Debugger {
             calldata: interp.contract().input.clone(),
             returndata: interp.return_data_buffer.clone(),
             instruction: Instruction::OpCode(op),
-            push_bytes,
+            push_bytes: push_bytes.unwrap_or_default(),
             total_gas_used,
         });
     }