Improved JIT Compiler Optimizations

The improved JIT compiler optimizations instructs the Java Virtual Machine to favor ultimate execution speed over the startup time of Java applications. The JIT compiler performs new optimizations for both SPARC and Intel (IA) platforms, including inlining of virtual and non-virtual methods, CSE within extended basic blocks, loop analysis to eliminate array bounds checking, and fast type checks.

Inlining

Java 2 SDK for Solaris provides inlining, which eliminates the need to inline manually (and risk destroying program modularity). Automatic inlining is restricted to relatively small, non-synchronous methods without flow control.

Mixed-Mode Execution

Java 2 SDK for Solaris includes a new mixed-mode execution feature that can significantly improve performance. Mixed-mode execution occurs when the VM compiles only the performance-critical methods and interprets the rest. This feature reduces compilation overhead, enables programs to start more quickly, and lets the VM spend more time compiling and optimizing where it matters most, enabling better performance.

Mixed-mode execution is the default mode. In mixed mode, the VM divides the methods into two types:

• Methods that might contain loops

• Methods that do not contain loops

For each type, the JIT compiler determines when compilation occurs. Methods that potentially contain loops are compiled on their first execution. Methods that do not contain loops are compiled on the 15th invocation.