Editing ARM architecture family (section)

==={{anchor|ThumbEE}}Thumb Execution Environment (ThumbEE)===
''ThumbEE'' (erroneously called ''Thumb-2EE'' in some ARM documentation), which was marketed as Jazelle RCT<ref>{{cite web |url=https://www.arm.com/products/processors/technologies/jazelle.php |archive-url=https://web.archive.org/web/20170602084751/https://www.arm.com/products/processors/technologies/jazelle.php |title=Jazelle |publisher=ARM Ltd. |url-status=dead |archive-date=2 June 2017}}</ref> (Runtime Compilation Target), was announced in 2005 and deprecated in 2011. It first appeared in the ''Cortex-A8'' processor. ThumbEE is a fourth instruction set state, making small changes to the Thumb-2 extended instruction set. These changes make the instruction set particularly suited to code generated at runtime (e.g. by [[just-in-time compilation|JIT compilation]]) in managed ''Execution Environments''. ThumbEE is a target for languages such as [[Java (programming language)|Java]], [[C Sharp (programming language)|C#]], [[Perl]], and [[Python (programming language)|Python]], and allows [[Just-in-time compilation|JIT compilers]] to output smaller compiled code without reducing performance.{{citation needed|date=June 2020}}

New features provided by ThumbEE include automatic null pointer checks on every load and store instruction, an instruction to perform an array bounds check, and special instructions that call a handler. In addition, because it utilises Thumb-2 technology, ThumbEE provides access to registers r8–r15 (where the Jazelle/DBX Java VM state is held).<ref>{{cite web |url=https://www.arm.com/miscPDFs/10069.pdf |title=ARM strengthens Java compilers: New 16-Bit Thumb-2EE Instructions Conserve System Memory |author=Tom R. Halfhill |year=2005 |archive-url=https://web.archive.org/web/20071005161753/https://www.arm.com/miscPDFs/10069.pdf |archive-date=5 October 2007}}</ref> Handlers are small sections of frequently called code, commonly used to implement high level languages, such as allocating memory for a new object. These changes come from repurposing a handful of opcodes, and knowing the core is in the new ThumbEE state.

On 23 November 2011, Arm deprecated any use of the ThumbEE instruction set,<ref>ARM Architecture Reference Manual, Armv7-A and Armv7-R edition, issue C.b, Section A2.10, 25 July 2012.</ref> and Armv8 removes support for ThumbEE.