Use instruction pointer instead of index

lib/evmone/analysis.hpp

@@ -56,11 +56,11 @@ struct evm_stack
     uint256 pop() noexcept { return *top_item--; }
 };
 
+struct instr_info;
+
 struct execution_state
 {
-    static constexpr auto stop_sentinel = std::numeric_limits<size_t>::max();
-
-    size_t pc = 0;
+    const instr_info* next_instr{nullptr};
     evmc_status_code status = EVMC_SUCCESS;
     int64_t gas_left = 0;
 
@@ -91,7 +91,7 @@ struct execution_state
     void exit(evmc_status_code status_code) noexcept
     {
         status = status_code;
-        pc = stop_sentinel;
+        next_instr = nullptr;
     }
 };
 

lib/evmone/execution.cpp

@@ -22,18 +22,19 @@ evmc_result execute(evmc_instance*, evmc_context* ctx, evmc_revision rev, const
 
     auto state = std::make_unique<execution_state>();
     state->analysis = &analysis;
+    state->next_instr = &state->analysis->instrs[0];
     state->msg = msg;
     state->code = code;
     state->code_size = code_size;
     state->host = evmc::HostContext{ctx};
     state->gas_left = msg->gas;
     state->rev = rev;
-    while (state->pc != execution_state::stop_sentinel)
+    while (state->next_instr)
     {
-        auto& instr = analysis.instrs[state->pc];
+        const auto& instr = *state->next_instr;
 
-        // Advance the PC to allow jump opcodes to overwrite it.
-        ++state->pc;
+        // Advance next_instr to allow jump opcodes to overwrite it.
+        ++state->next_instr;
 
         instr.fn(*state, instr.arg);
     }

lib/evmone/instructions.cpp

@@ -484,7 +484,7 @@ void op_jump(execution_state& state, instr_argument) noexcept
         (pc = state.analysis->find_jumpdest(static_cast<int>(dst))) < 0)
         return state.exit(EVMC_BAD_JUMP_DESTINATION);
 
-    state.pc = static_cast<size_t>(pc);
+    state.next_instr = &state.analysis->instrs[static_cast<size_t>(pc)];
 }
 
 void op_jumpi(execution_state& state, instr_argument arg) noexcept