The Rust team knew from the outset that repurposing a C++ backend was the only pragmatic way to compete with C++ on performance given their manpower constraints and projected timeframe. Even if all available backends had required the use of GPL, Rust would have still chosen one and moved forward with it.<p>Fortunately, given that Graydon did prefer a permissive license for the compiler, LLVM provided exactly what he was looking for.