![]() ![]() The first generates machine code during the execution of the program itself (i.e., shortly before the first invocation of a Java method). There are two main compilation strategies in Java: Just in Time Compilation (JIT) and Ahead of Time Compilation (AOT). Now that we understand the role of compilers, let’s talk about when is the compilation performed. Optimizations in the C2 compiler include global value numbering, conditional constant type propagation, constant folding, global code motion, algebraic identities, method inlining (aggressive, optimistic, and/or multi-morphic), intrinsic replacement, loop transformations (unswitching, unrolling), array range check elimination, and others. Colors are machine states, including local, global, and argument registers and stack. ![]() It has a graph-coloring register allocator. The C2 compiler is a highly optimizing bytecode compiler that uses a “sea of nodes” SSA “ideal” IR, which lowers to a machine-specific IR of the same kind. It uses a simple CFG-oriented SSA “high” IR, a machine-oriented “low” IR, a linear scan register allocation, and a template-style code generator. ![]() The C1 compiler is a fast, lightly optimizing bytecode compiler that performs some value numbering, inlining, and class analysis. In terms of compiler optimizations in the standard Java Hotspot Virtual Machine, there are two major compilers: the C1 compiler and the C2 compiler. The quantity and complexity of these optimizations have increased significantly in the last decades. The goal of a compiler is to create a consistent executable of the compiled program.Ī consistent executable is one that is attained to the specification that is written in the source code, runs fast, and it is safe.Ĭompilers perform several optimizations during the machine code generation phase.įor example, most compilers perform constant inlining, loop unrolling, and partial evaluation at compilation time, to name a few. Machine code are low-level instructions tailored to execute in a particular microprocessor.Ĭompilers are programs designed to perform this task efficiently. Compilation in JavaĬompiling a program means transforming source code from a high-level programming language, such as Java or Python, into machine code. In this post, I’ll explain the differences between these two compilation strategies.Īfter reading this post, you will learn what Java compilers do, the differences between existing compiling approaches, and in which circumstances using an AOT compiler is more appropriate. The latter is supported by the novel GraalVM compiler and allows statically compiling bytecode directly into machine code at build time. The first is the default mode, and it is used by the Java Hotspot Virtual Machine to translate bytecode into machine code at runtime. There are two ways of compiling a Java application: using Just in Time Compilation (JIT) or Ahead of Time Compilation (AOT). ![]()
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