High performance annotation-aware JVM for Java cards

Early applications of smart cards have focused in the area of personal security. Recently, there has been an increasing demand for networked, multi-application cards. In this new scenario, enhanced application-specific on-card Java applets and complex cryptographic services are executed through the smart card Java Virtual Machine (JVM). In order to support such computation-intensive applications, contemporary smart cards are designed with built-in microprocessors and memory. As smart cards are highly area-constrained environments with memory, CPU and peripherals competing for a very small die space, the VM execution engine of choice is often a small, slow interpreter. In addition, support for multiple applications and cryptographic services demands high performance VM execution engine. The above necessitates the optimization of the JVM for Java Cards.In this paper we present the concept of an annotation-aware interpreter that optimizes the interpreted execution of Java code using Java bytecode SuperOperators (SOs). SOs are groups of bytecode operations that are executed as a specialized VM instruction. Simultaneous translation of all the bytecode operations in an SO reduces the bytecode dispatch cost and the number of stack accesses (data transfer to/from the Java operand stack) and stack pointer updates. Furthermore, SOs help improve native code quality without hindering class file portability. Annotation attributes in the class files mark the occurrences of valuable SOs, thereby dispensing the expensive task of searching and selecting SOs at runtime. Besides, our annotation-based approach incurs minimal memory overhead as opposed to just-in-time (JIT) compilers.We obtain an average speedup of 18% using an interpreter customized with the top SOs formed from operation folding patterns. Further, we show that greater speedups could be achieved by statically adding to the interpreter application-specific SOs formed by top basic blocks. The effectiveness of our approach is evidenced by performance improvements of (upto) 131% obtained using SOs formed from optimized basic blocks.