perf(levm): use a stack pool

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Perf
 
+### 2025-06-30
+
+- Use a stack pool [#3386](https://github.com/lambdaclass/ethrex/pull/3386)
+
 ### 2025-06-27
 
 - Reduce handle_debug runtime cost [#3356](https://github.com/lambdaclass/ethrex/pull/3356)

crates/vm/levm/src/call_frame.rs

@@ -102,6 +102,10 @@ impl Stack {
         self.values.swap(self.offset, index);
         Ok(())
     }
+
+    pub fn clear(&mut self) {
+        self.offset = STACK_LIMIT;
+    }
 }
 
 impl Default for Stack {
@@ -231,6 +235,7 @@ impl CallFrame {
         is_create: bool,
         ret_offset: U256,
         ret_size: usize,
+        stack: Stack,
     ) -> Self {
         let invalid_jump_destinations =
             get_invalid_jump_destinations(&bytecode).unwrap_or_default();
@@ -250,6 +255,7 @@ impl CallFrame {
             is_create,
             ret_offset,
             ret_size,
+            stack,
             ..Default::default()
         }
     }

crates/vm/levm/src/opcode_handlers/system.rs

@@ -684,6 +684,9 @@ impl<'a> VM<'a> {
             return Ok(OpcodeResult::Continue { pc_increment: 1 });
         }
 
+        let mut stack = self.stack_pool.pop().unwrap_or_default();
+        stack.clear();
+
         let new_call_frame = CallFrame::new(
             deployer,
             new_address,
@@ -698,6 +701,7 @@ impl<'a> VM<'a> {
             true,
             U256::zero(),
             0,
+            stack,
         );
         self.call_frames.push(new_call_frame);
 
@@ -752,6 +756,9 @@ impl<'a> VM<'a> {
             return Ok(OpcodeResult::Continue { pc_increment: 1 });
         }
 
+        let mut stack = self.stack_pool.pop().unwrap_or_default();
+        stack.clear();
+
         let new_call_frame = CallFrame::new(
             msg_sender,
             to,
@@ -766,6 +773,7 @@ impl<'a> VM<'a> {
             false,
             ret_offset,
             ret_size,
+            stack,
         );
         self.call_frames.push(new_call_frame);
 
@@ -859,6 +867,11 @@ impl<'a> VM<'a> {
         };
 
         self.tracer.exit_context(ctx_result, false)?;
+
+        let mut stack = executed_call_frame.stack;
+        stack.clear();
+        self.stack_pool.push(stack);
+
         Ok(())
     }
 
@@ -901,6 +914,11 @@ impl<'a> VM<'a> {
         };
 
         self.tracer.exit_context(ctx_result, false)?;
+
+        let mut stack = executed_call_frame.stack;
+        stack.clear();
+        self.stack_pool.push(stack);
+
         Ok(())
     }
 

crates/vm/levm/src/vm.rs

@@ -1,6 +1,6 @@
 use crate::{
     TransientStorage,
-    call_frame::CallFrame,
+    call_frame::{CallFrame, Stack},
     db::gen_db::GeneralizedDatabase,
     debug::DebugMode,
     environment::Environment,
@@ -59,6 +59,8 @@ pub struct VM<'a> {
     pub tracer: LevmCallTracer,
     /// Mode for printing some useful stuff, only used in development!
     pub debug_mode: DebugMode,
+    /// A pool of stacks to avoid reallocating too much when creating new call frames.
+    pub stack_pool: Vec<Stack>,
     pub vm_type: VMType,
 }
 
@@ -83,6 +85,7 @@ impl<'a> VM<'a> {
             storage_original_values: HashMap::new(),
             tracer,
             debug_mode: DebugMode::disabled(),
+            stack_pool: Vec::new(),
             vm_type,
         }
     }
@@ -111,6 +114,7 @@ impl<'a> VM<'a> {
             is_create,
             U256::zero(),
             0,
+            Stack::default(),
         );
 
         self.call_frames.push(initial_call_frame);