https://deepjava.org/ 2026-04-14T22:23:16+00:00 https://deepjava.org/ https://deepjava.org/lib/tpl/deepjava-tpl/images/favicon.ico text/html 2022-12-20T11:24:27+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/arrays?rev=1671531867&do=diff Arrays The following figure demonstrates how arrays are implemented in the memory. Implementation of an array An array extends java/lang/object. The field Tag points to the type descriptor of this array ([ClassA for this example). The single array elements themselves are of type text/html 2020-06-18T21:29:43+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/cfg?rev=1592508583&do=diff Control Flow Graph The Control Flow Graph is an intermediate form where the instructions and the control flow are shown as a directed graph. It enables certain optimizations. For each method of a class an own CFG is built. Nodes in such a CFG represent a sequence of instructions with no branches. Further, there must be no branch target within a node. Branches in a method are represented by directed edges which connect the nodes. Each node has n predecessors and m successors as well as an index … text/html 2022-12-20T11:20:46+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/cfr?rev=1671531646&do=diff Class File Reader Course of Action Build System classes as indicated by the configuration are loaded first. After this the root classes are loaded. For each class all other classes which are referenced in the constant pool and which have a class file (arrays may be referenced but have no class files) are kept in an import list and subsequently loaded. text/html 2021-05-10T19:52:40+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/class_initialization?rev=1620669160&do=diff Initialization Initialize Classes The Java compiler packes all initialization of static variables into a method called clinit. This is the class constructor. As an example the following source file with blocks 1 to 4 will be converted into Bytecode and is put linearly into text/html 2022-09-30T10:20:04+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/fields_of_item?rev=1664526004&do=diff Use of Index, Offset and Address of an Item These fields have different meanings according to what a given item represents. Note: Statements in brackets denote a type, e.g. [Class] means an item of type org.deepjava.classItems.Class. Classes [Class] text/html 2019-07-11T19:34:46+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/interfaces?rev=1562866486&do=diff Interfaces Interfaces generally don't have to be translated. All fields are constant and the methods are abstract. Interfaces don't need a type descriptor with a single exception as mentioned in Type Descriptors. They also don't need a constant block and don't have to be included in the system table compared to regular classes (see text/html 2018-11-21T15:25:46+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/objects?rev=1542810346&do=diff Objects Objects on the heap need a reference to their type descriptor (Tag) and information for the garbage collection. Implementation of an object The field size allows for a faster sweep phase during garbage collection. size includes the size of the object plus heap field and text/html 2022-12-20T11:31:35+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/ssa?rev=1671532295&do=diff Static Single Assignment Form The Static Single Assignment Form (SSA) is an intermediate form which allows various optimizations and facilitates register allocation. The main point of the SSA is that each variable is assigned a value only once. Each new assignment leads to a new instance of this variable (indicated by i text/html 2018-11-02T17:28:16+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/start?rev=1541176096&do=diff Crosscompiler The crosscompiler comprises three main steps which are platform independent as shown in the next figure. Further entries treat how arrays or interfaces are handled or how type checking is performed. Steps of cross compilation Components, platform independent text/html 2016-02-25T13:33:05+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/strings?rev=1456403585&do=diff Implementation of Strings In Java a string like String str = new String("abc"); causes the allocation of two objects. Strings in Java are immutable. With the field offset it is possible to form substrings in the constant string. A string in Java text/html 2022-12-20T11:43:28+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/type_checking?rev=1671533008&do=diff Type Checking For Bytecode instructions checkcast and instanceof the type must be checked during runtime. Two cases must be considered: checking for an array class or checking for a regular class. Checking for interfaces is discussed below. Since the dynamic type of an object cannot be known the type checking for any type must work properly. The following table shows all possible casses. ClassA is a regular class, text/html 2019-07-11T19:12:06+00:00 Anonymous (anonymous@undisclosed.example.com) https://deepjava.org/dev/crosscompiler/type_descriptor?rev=1562865126&do=diff Type Descriptor Each class needs a type descriptor in the constant block of this class (see Linker32). This type descriptor will be needed to find instance methods or to do type checking. All arrays - even arrays with elements being of an interface type - need a type descriptor. Interfaces themselves need no type descriptor because there cannot be instances of interfaces.