SafeTSA (Safe Typed Single Assignment) is a static single assignment form (SSA) intermediate representation capable of representing all of the type safety of the Java programming language and the standard Java Virtual Machine (JVM) byte-code.
A typical just-in-time compiler for a JVM converts JVM stack-machine byte-code into an internal static-single-assignment representation, performs optimizations, converts the SSA form to a low-level form similar to the host CPU's machine code, and performs some platform-specific optimizations before finally creating the native code that gets executed.
SafeTSA is an external representation similar to these SSA internal representations, yet SafeTSA still provides the full type safety (including security verifiability at class load time) of standard JVM byte-code.
They then ran a standard suite of Java benchmarks and published a paper showing that SafeTSA input produced faster running native code output from the just-in-time compiler.
In addition, the researchers also showed that SafeTSA required less time to compile to native code.