From b2e548458d73551e4421fe6db0fa5424ec2e00bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <pawel@ethereum.org>
Date: Sun, 1 Sep 2024 13:55:21 +0200
Subject: [PATCH] baseline: VM-level ExecutionStates

---
 lib/evmone/vm.cpp | 18 ++++++++++++++++--
 lib/evmone/vm.hpp |  7 ++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/lib/evmone/vm.cpp b/lib/evmone/vm.cpp
index 014ebca00c..fbfa91bb70 100644
--- a/lib/evmone/vm.cpp
+++ b/lib/evmone/vm.cpp
@@ -72,7 +72,7 @@ evmc_set_option_result set_option(evmc_vm* c_vm, char const* c_name, char const*
 }  // namespace
 
 
-inline constexpr VM::VM() noexcept
+VM::VM() noexcept
   : evmc_vm{
         EVMC_ABI_VERSION,
         "evmone",
@@ -82,7 +82,21 @@ inline constexpr VM::VM() noexcept
         evmone::get_capabilities,
         evmone::set_option,
     }
-{}
+{
+    m_execution_states.reserve(1025);
+}
+
+ExecutionState& VM::get_execution_state(size_t depth) noexcept
+{
+    // Vector already has the capacity for all possible depths,
+    // so reallocation never happens (therefore: noexcept).
+    // TODO: Maybe just use std::array?
+    // FIXME: unit test where max depth is reached is needed.
+    assert(depth < m_execution_states.capacity());
+    if (m_execution_states.size() <= depth)
+        m_execution_states.resize(depth + 1);
+    return m_execution_states[depth];
+}
 
 }  // namespace evmone
 
diff --git a/lib/evmone/vm.hpp b/lib/evmone/vm.hpp
index 34bcd4a920..6549e3ae3e 100644
--- a/lib/evmone/vm.hpp
+++ b/lib/evmone/vm.hpp
@@ -3,8 +3,10 @@
 // SPDX-License-Identifier: Apache-2.0
 #pragma once
 
+#include "execution_state.hpp"
 #include "tracing.hpp"
 #include <evmc/evmc.h>
+#include <vector>
 
 #if defined(_MSC_VER) && !defined(__clang__)
 #define EVMONE_CGOTO_SUPPORTED 0
@@ -22,10 +24,13 @@ class VM : public evmc_vm
     bool validate_eof = false;
 
 private:
+    std::vector<ExecutionState> m_execution_states;
     std::unique_ptr<Tracer> m_first_tracer;
 
 public:
-    inline constexpr VM() noexcept;
+    VM() noexcept;
+
+    [[nodiscard]] ExecutionState& get_execution_state(size_t depth) noexcept;
 
     void add_tracer(std::unique_ptr<Tracer> tracer) noexcept
     {