readme: Describe Advanced and Baseline interpreters

README.md

@@ -14,20 +14,38 @@ Created by members of the [Ewasm] team, the project aims for clean, standalone E
 that can be imported as an execution module by Ethereum Client projects. 
 The codebase of _evmone_ is optimized to provide fast and efficient execution of EVM smart contracts.
 
-#### Characteristic of evmone
+### Characteristic of evmone
 
 1. Exposes the [EVMC] API.
-2. The _indirect call threading_ is the dispatch method used -
+2. Requires C++17 standard.
+3. The [intx] library is used to provide 256-bit integer precision.
+4. The [ethash] library is used to provide Keccak hash function implementation
+   needed for the special `KECCAK256` instruction.
+5. Contains two interpreters: **Advanced** (default) and **Baseline** (experimental).
+
+### Advanced Interpreter
+
+1. The _indirect call threading_ is the dispatch method used -
    a loaded EVM program is a table with pointers to functions implementing virtual instructions.
-3. The gas cost and stack requirements of block of instructions is precomputed 
+2. The gas cost and stack requirements of block of instructions is precomputed 
    and applied once per block during execution.
-4. The [intx] library is used to provide 256-bit integer precision.
-5. The [ethash] library is used to provide Keccak hash function implementation
-   needed for the special `SHA3` instruction.
-6. Requires C++17 standard.
+3. Performs extensive and expensive bytecode analysis before execution.
+
+### Baseline Interpreter
+
+1. Provides relatively straight-forward EVM implementation.
+2. Performs only minimalistic `JUMPDEST` analysis.
+3. Experimental. Can be enabled with `O=0` option.
+
 
 ## Usage
 
+### Optimization levels
+
+The option `O` controls the "optimization level":
+- `O=2` uses Advanced interpreter (default),
+- `O=0` uses Baseline interpreter.
+
 ### As geth plugin
 
 evmone implements the [EVMC] API for Ethereum Virtual Machines.