Support for more debugging intrnals ART supports a number of new debugging options, particularly in monitor- and garbage collection-related functionality. Navigation menu Personal tools Log in Request account. Content and code samples on this page are subject to the licenses described in the Content License. ART supports a number of new debugging options, particularly in monitor- and garbage collection-related functionality.
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Architecture[ edit ] A comparison of Dalvik and ART architectures Unlike Java Virtual Machines , which are stack machines , the Dalvik VM uses a register-based architecture that requires fewer, typically more complex, virtual machine instructions. Dalvik programs are written in Java using the Android application programming interface API , compiled to Java bytecode, and converted to Dalvik instructions as necessary.
A tool called dx is used to convert Java. Multiple classes are included in a single. Duplicate strings and other constants used in multiple class files are included only once in the. Java bytecode is also converted into an alternative instruction set used by the Dalvik VM. An uncompressed. In order to gain further optimizations , byte order may be swapped in certain data, simple data structures and function libraries may be linked inline , and empty class objects may be short-circuited, for example.
Being optimized for low memory requirements, Dalvik has some specific characteristics that differentiate it from other standard VMs:  The VM was slimmed down to use less space. The constant pool has been modified to use only bit indices to simplify the interpreter.
Standard Java bytecode executes 8-bit stack instructions. Local variables must be copied to or from the operand stack by separate instructions. Dalvik instead uses its own bit instruction set that works directly on local variables.
The local variable is commonly picked by a 4-bit "virtual register" field. According to Google, the design of Dalvik permits a device to run multiple instances of the VM efficiently. This difference is of importance to VM interpreters, for which opcode dispatch tends to be expensive, along with other factors similarly relevant to just-in-time compilation.
Google Dalvik is published under the terms of the Apache License 2. Oracle and some reviewers dispute this.
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