Bytecode: Difference between revisions

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
← Previous edit
VisualWikitext
imported>DreamRimmer bot II
m Standardise list-defined references format (bot)
imported>Kvng
m unpiped links using script
 
Line 5: Line 5:
{{Program execution}}
{{Program execution}}


'''Bytecode''' (also called '''portable code''' or '''p-code''') is a form of [[instruction set]] designed for efficient execution by a software [[interpreter (computing)|interpreter]]. Unlike [[Human-readable code|human-readable]]<ref name="Dynamic_Machine_Code"/> [[source code]], bytecodes are compact numeric codes, constants, and references (normally numeric addresses) that encode the result of [[compiler]] parsing and performing [[Semantic analysis (compilers)|semantic analysis]] of things like type, scope, and nesting depths of program objects.
'''Bytecode''' (also called '''portable code''' or '''p-code''') is an [[intermediate representation]] form of [[instruction set]] designed for efficient execution by a software [[interpreter (computing)|interpreter]]. Unlike [[Human-readable code|human-readable]]<ref name="Dynamic_Machine_Code"/> [[source code]], bytecodes are compact numeric codes, constants, and references (normally numeric addresses) that encode the result of [[compiler]] parsing and performing [[Semantic analysis (compilers)|semantic analysis]] of things like type, scope, and nesting depths of program objects.


The name ''bytecode'' stems from instruction sets that have one-[[byte]] [[opcode]]s followed by optional parameters. [[Intermediate representation]]s such as bytecode may be output by [[programming language]] implementations to ease [[interpreter (computing)|interpretation]], or it may be used to reduce hardware and [[operating system]] dependence by allowing the same code to run [[cross-platform]], on different devices. Bytecode may often be either directly executed on a [[virtual machine]] (a [[p-code machine]], i.e., interpreter), or it may be further compiled into [[machine code]] for better performance.
The name ''bytecode'' stems from instruction sets that have one-[[byte]] [[opcode]]s followed by optional parameters. Intermediate representations such as bytecode may be output by [[programming language]] implementations to ease [[interpreter (computing)|interpretation]], or it may be used to reduce hardware and [[operating system]] dependence by allowing the same code to run [[cross-platform]], on different devices. Bytecode may often be either directly executed on a [[virtual machine]] (a [[p-code machine]], i.e., interpreter), or it may be further compiled into [[machine code]] for better performance.


Since bytecode instructions are processed by software, they may be arbitrarily complex, but are nonetheless often akin to traditional hardware instructions: virtual [[stack machine]]s are the most common, but virtual [[register machine]]s have been built also.<ref name="Jucs_Lua"/><ref name="Dalvik"/> Different parts may often be stored in separate files, similar to [[object file|object modules]], but dynamically loaded during execution.
Since bytecode instructions are processed by software, they may be arbitrarily complex, but are nonetheless often akin to traditional hardware instructions: virtual [[stack machine]]s are the most common, but virtual [[register machine]]s have been built also.<ref name="Jucs_Lua"/><ref name="Dalvik"/> Different parts may often be stored in separate files, similar to [[object file|object modules]], but dynamically loaded during execution.
Line 14: Line 14:
A bytecode program may be executed by parsing and ''directly'' executing the instructions, one at a time. This kind of ''bytecode interpreter'' is very portable. Some systems, called dynamic translators, or ''[[just-in-time compilation|just-in-time]]'' (JIT) compilers, translate bytecode into [[machine code]] as necessary at [[Run time (program lifecycle phase)|runtime]]. This makes the virtual machine hardware-specific but does not lose the portability of the bytecode. For example, [[Java (programming language)|Java]] and [[Smalltalk]] code is typically stored in bytecode format, which is typically then JIT compiled to translate the bytecode to machine code before execution. This introduces a delay before a program is run, when the bytecode is compiled to native machine code, but improves execution speed considerably compared to interpreting source code directly, normally by around an order of magnitude (10x).<ref name="Byte_Machine"/>
A bytecode program may be executed by parsing and ''directly'' executing the instructions, one at a time. This kind of ''bytecode interpreter'' is very portable. Some systems, called dynamic translators, or ''[[just-in-time compilation|just-in-time]]'' (JIT) compilers, translate bytecode into [[machine code]] as necessary at [[Run time (program lifecycle phase)|runtime]]. This makes the virtual machine hardware-specific but does not lose the portability of the bytecode. For example, [[Java (programming language)|Java]] and [[Smalltalk]] code is typically stored in bytecode format, which is typically then JIT compiled to translate the bytecode to machine code before execution. This introduces a delay before a program is run, when the bytecode is compiled to native machine code, but improves execution speed considerably compared to interpreting source code directly, normally by around an order of magnitude (10x).<ref name="Byte_Machine"/>


Because of its performance advantage, today many language implementations execute a program in two phases, first compiling the source code into bytecode, and then passing the bytecode to the virtual machine. There are bytecode based virtual machines of this sort for [[Java (programming language)|Java]], [[Raku (programming language)|Raku]], [[Python (programming language)|Python]], [[PHP]],{{efn|PHP has [[just-in-time compilation]] in PHP 8,<ref>{{Cite web|last=O’Phinney|first=Matthew Weier|title=Exploring the New PHP JIT Compiler|url=https://www.zend.com/blog/exploring-new-php-jit-compiler|access-date=2021-02-19|website=Zend by Perforce|language=en}}</ref><ref>{{Cite web|title=PHP 8: The JIT - stitcher.io|url=https://stitcher.io/blog/php-jit|access-date=2021-02-19|website=stitcher.io|language=en}}</ref> and before while not on in the default version, had options like [[HHVM]]. For older versions of PHP: Although [[PHP]] opcodes are generated each time the program is launched, and are always interpreted and not [[just-in-time compilation|just-in-time compiled]].}} [[Tcl]], [[AWK|mawk]] and [[Forth (programming language)|Forth]] (however, Forth is seldom compiled via bytecodes in this way, and its virtual machine is more generic instead). The implementation of [[Perl]] and [[Ruby (programming language)|Ruby]] 1.8 instead work by walking an [[abstract syntax tree]] representation derived from the source code.
Because of its performance advantage, today many language implementations execute a program in two phases, first compiling the source code into bytecode, and then passing the bytecode to the virtual machine. There are bytecode based virtual machines of this sort for [[Java (programming language)|Java]], [[Raku (programming language)|Raku]], [[Python (programming language)|Python]], [[PHP]],{{efn|PHP has [[just-in-time compilation]] in PHP 8,<ref>{{Cite web|last=O’Phinney|first=Matthew Weier|title=Exploring the New PHP JIT Compiler|url=https://www.zend.com/blog/exploring-new-php-jit-compiler|access-date=2021-02-19|website=Zend by Perforce|language=en}}</ref><ref>{{Cite web|title=PHP 8: The JIT - stitcher.io|url=https://stitcher.io/blog/php-jit|access-date=2021-02-19|website=stitcher.io|language=en}}</ref> and before while not on in the default version, had options like [[HHVM]]. For older versions of PHP: Although [[PHP]] opcodes are generated each time the program is launched, and are always interpreted and not [[just-in-time compiled]].}} [[Tcl]], [[AWK|mawk]] and [[Forth (programming language)|Forth]] (however, Forth is seldom compiled via bytecodes in this way, and its virtual machine is more generic instead). The implementation of [[Perl]] and [[Ruby (programming language)|Ruby]] 1.8 instead work by walking an [[abstract syntax tree]] representation derived from the source code.


More recently, the authors of [[V8 (JavaScript engine)|V8]]<ref name="Dynamic_Machine_Code"/> and [[Dart (programming language)|Dart]]<ref name="Loitsch_Bytecode"/> have challenged the notion that intermediate bytecode is needed for fast and efficient VM implementation. Both of these language implementations currently do direct JIT compiling from source code to machine code with no bytecode intermediary.<ref name="Javascript"/>
More recently, the authors of [[V8 (JavaScript engine)|V8]]<ref name="Dynamic_Machine_Code"/> and [[Dart (programming language)|Dart]]<ref name="Loitsch_Bytecode"/> have challenged the notion that intermediate bytecode is needed for fast and efficient VM implementation. Both of these language implementations currently do direct JIT compiling from source code to machine code with no bytecode intermediary.<ref name="Javascript"/>
Line 30: Line 30:
*[[CMUCL]] and Scieneer Common Lisp implementations of [[Common Lisp]] can compile either to native code or to bytecode, which is far more compact
*[[CMUCL]] and Scieneer Common Lisp implementations of [[Common Lisp]] can compile either to native code or to bytecode, which is far more compact
*[[Common Intermediate Language]] executed by [[Common Language Runtime]], used by [[.NET]] languages such as [[C Sharp (programming language)|C#]]
*[[Common Intermediate Language]] executed by [[Common Language Runtime]], used by [[.NET]] languages such as [[C Sharp (programming language)|C#]]
*[[Dalvik (software)|Dalvik]] bytecode, designed for the [[Android (operating system)|Android]] platform, is executed by the [[Dalvik (software)|Dalvik virtual machine]]
*[[Dalvik (software)|Dalvik]] bytecode, designed for the [[Android (operating system)|Android]] platform, is executed by the [[Dalvik virtual machine]]
*Dis bytecode, designed for the [[Inferno (operating system)]], is executed by the [[Dis virtual machine]]
*Dis bytecode, designed for the [[Inferno (operating system)]], is executed by the [[Dis virtual machine]]
*[[EiffelStudio]] for the [[Eiffel (programming language)|Eiffel]] programming language
*[[EiffelStudio]] for the [[Eiffel (programming language)|Eiffel]] programming language
Line 63: Line 63:
*[[LLVM IR]]
*[[LLVM IR]]
*LSL, a scripting language used in virtual worlds compiles into bytecode running on a virtual machine. Second Life has the original Mono version, Inworldz developed the Phlox version.
*LSL, a scripting language used in virtual worlds compiles into bytecode running on a virtual machine. Second Life has the original Mono version, Inworldz developed the Phlox version.
*[[Lua (programming language)|Lua]] language uses a register-based bytecode virtual machine
*[[Lua]] language uses a register-based bytecode virtual machine
*m-code of the [[MATLAB]] language<ref name="Patent_6973644"/>
*m-code of the [[MATLAB]] language<ref name="Patent_6973644"/>
*[[Malbolge]] is an [[esoteric programming language|esoteric]] [[machine language]] for a ternary virtual machine.
*[[Malbolge]] is an [[esoteric programming language|esoteric]] [[machine language]] for a ternary virtual machine.
Line 124: Line 124:
<ref name="cran_r">{{Cite web|url=https://cran.r-project.org/doc/manuals/R-admin.html#Byte_002dcompiler|title=R Installation and Administration|website=cran.r-project.org}}</ref>
<ref name="cran_r">{{Cite web|url=https://cran.r-project.org/doc/manuals/R-admin.html#Byte_002dcompiler|title=R Installation and Administration|website=cran.r-project.org}}</ref>
<ref name="SQLite">{{cite web |title=The SQLite Bytecode Engine |url=https://www.sqlite.org/opcode.html |access-date=29 August 2016 |archive-url=https://web.archive.org/web/20170414044139/http://sqlite.org/opcode.html |archive-date=14 April 2017 |url-status=dead }}</ref>
<ref name="SQLite">{{cite web |title=The SQLite Bytecode Engine |url=https://www.sqlite.org/opcode.html |access-date=29 August 2016 |archive-url=https://web.archive.org/web/20170414044139/http://sqlite.org/opcode.html |archive-date=14 April 2017 |url-status=dead }}</ref>
<ref name="Multiplan">{{cite book |title=Microsoft C Pcode Specifications |page=13 |quote=[[Multiplan]] wasn't compiled to [[machine code]], but to a kind of byte-code which was run by an [[interpreter (computing)|interpreter]], in order to make Multiplan portable across the widely varying hardware of the time. This byte-code distinguished between the machine-specific [[floating point format]] to calculate on, and an external (standard) format, which was [[binary-coded decimal|binary coded decimal]] (BCD). The PACK and UNPACK instructions converted between the two.}}</ref>
<ref name="Multiplan">{{cite book |title=Microsoft C Pcode Specifications |page=13 |quote=[[Multiplan]] wasn't compiled to [[machine code]], but to a kind of byte-code which was run by an [[interpreter (computing)|interpreter]], in order to make Multiplan portable across the widely varying hardware of the time. This byte-code distinguished between the machine-specific [[floating point format]] to calculate on, and an external (standard) format, which was [[binary coded decimal]] (BCD). The PACK and UNPACK instructions converted between the two.}}</ref>
</references>
</references>


[[Category:Bytecodes| ]]
[[Category:Bytecodes| ]]
[[Category:Virtualization]]
[[Category:Virtualization]]

Latest revision as of 15:41, 27 December 2025

Template:Short description Script error: No such module "Redirect hatnote". Script error: No such module "Unsubst". Template:Use dmy dates Template:Program execution

Bytecode (also called portable code or p-code) is an intermediate representation form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable[1] source code, bytecodes are compact numeric codes, constants, and references (normally numeric addresses) that encode the result of compiler parsing and performing semantic analysis of things like type, scope, and nesting depths of program objects.

The name bytecode stems from instruction sets that have one-byte opcodes followed by optional parameters. Intermediate representations such as bytecode may be output by programming language implementations to ease interpretation, or it may be used to reduce hardware and operating system dependence by allowing the same code to run cross-platform, on different devices. Bytecode may often be either directly executed on a virtual machine (a p-code machine, i.e., interpreter), or it may be further compiled into machine code for better performance.

Since bytecode instructions are processed by software, they may be arbitrarily complex, but are nonetheless often akin to traditional hardware instructions: virtual stack machines are the most common, but virtual register machines have been built also.[2][3] Different parts may often be stored in separate files, similar to object modules, but dynamically loaded during execution.

Execution

A bytecode program may be executed by parsing and directly executing the instructions, one at a time. This kind of bytecode interpreter is very portable. Some systems, called dynamic translators, or just-in-time (JIT) compilers, translate bytecode into machine code as necessary at runtime. This makes the virtual machine hardware-specific but does not lose the portability of the bytecode. For example, Java and Smalltalk code is typically stored in bytecode format, which is typically then JIT compiled to translate the bytecode to machine code before execution. This introduces a delay before a program is run, when the bytecode is compiled to native machine code, but improves execution speed considerably compared to interpreting source code directly, normally by around an order of magnitude (10x).[4]

Because of its performance advantage, today many language implementations execute a program in two phases, first compiling the source code into bytecode, and then passing the bytecode to the virtual machine. There are bytecode based virtual machines of this sort for Java, Raku, Python, PHP,Template:Efn Tcl, mawk and Forth (however, Forth is seldom compiled via bytecodes in this way, and its virtual machine is more generic instead). The implementation of Perl and Ruby 1.8 instead work by walking an abstract syntax tree representation derived from the source code.

More recently, the authors of V8[1] and Dart[5] have challenged the notion that intermediate bytecode is needed for fast and efficient VM implementation. Both of these language implementations currently do direct JIT compiling from source code to machine code with no bytecode intermediary.[6]

Examples

(disassemble '(lambda (x) (print x)))
; disassembly for (LAMBDA (X))
; 2436F6DF:       850500000F22     TEST EAX, [#x220F0000]     ; no-arg-parsing entry point
;       E5:       8BD6             MOV EDX, ESI
;       E7:       8B05A8F63624     MOV EAX, [#x2436F6A8]      ; #<FDEFINITION object for PRINT>
;       ED:       B904000000       MOV ECX, 4
;       F2:       FF7504           PUSH DWORD PTR [EBP+4]
;       F5:       FF6005           JMP DWORD PTR [EAX+5]
;       F8:       CC0A             BREAK 10                   ; error trap
;       FA:       02               BYTE #X02
;       FB:       18               BYTE #X18                  ; INVALID-ARG-COUNT-ERROR
;       FC:       4F               BYTE #X4F                  ; ECX
Compiled code can be analysed and investigated using a built-in tool for debugging the low-level bytecode. The tool can be initialized from the shell, for example:
>>> import dis # "dis" - Disassembler of Python byte code into mnemonics.
>>> dis.dis('print("Hello, World!")')
  1           0 LOAD_NAME                0 (print)
              2 LOAD_CONST               0 ('Hello, World!')
              4 CALL_FUNCTION            1
              6 RETURN_VALUE

See also

Template:Sister project

Notes

Template:Notelist

References

  1. ↑ a b Script error: No such module "citation/CS1".
  2. ↑ Script error: No such module "citation/CS1". (NB. This involves a register-based virtual machine.)
  3. ↑ Script error: No such module "citation/CS1". (NB. This VM is register based.)
  4. ↑ Script error: No such module "citation/CS1".
  5. ↑ Script error: No such module "citation/CS1".
  6. ↑ Script error: No such module "citation/CS1".
  7. ↑ Script error: No such module "citation/CS1".
  8. ↑ Script error: No such module "citation/CS1".
  9. ↑ Script error: No such module "citation/CS1".
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "citation/CS1". (NB. What is meant by "procedures" here are some additional bytecodes in the IBM KEYBOARD.SYS file not supported by the Microsoft version of the KEYB driver.)
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ Script error: No such module "citation/CS1".
Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Bytecode&oldid=4389234"