rfc:jit

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rfc:jit [2019/02/22 12:08] – Compatibility with C compilers without GCC explicit global register variables extension dmitryrfc:jit [2019/04/12 07:38] – old revision restored (2019/04/01 07:45) laruence
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 ====== PHP RFC: JIT ====== ====== PHP RFC: JIT ======
-  * Version: 0.9+  * Version: 1.0
   * Date: 2019-01-28   * Date: 2019-01-28
   * Author: Dmitry Stogov <dmitry@php.net>, Zeev Suraski <zeev@php.net>   * Author: Dmitry Stogov <dmitry@php.net>, Zeev Suraski <zeev@php.net>
-  * Status: Under Discussion+  * Status: Accepted (to be merged into PHP-8 only)
   * First Published at: https://wiki.php.net/rfc/jit   * First Published at: https://wiki.php.net/rfc/jit
  
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 When enabled, native code of PHP files is stored in an additional region of the OPcache shared memory and op_array->opcodes[].handler(s) keep pointers to the entry points of JIT-ed code. This approach doesn't require engine modification at all. When enabled, native code of PHP files is stored in an additional region of the OPcache shared memory and op_array->opcodes[].handler(s) keep pointers to the entry points of JIT-ed code. This approach doesn't require engine modification at all.
  
-We use DynAsm (developed for LuaJIT project) for generation of native code. It's a very lightweight and advanced tool, but does assume good, and very low-level development knowledge of target assembler languages.  In the past we tried LLVM, but its code generation speed was almost 100 times slower, making it prohibitively expensive to use. Currently we support only x86 and x86_64 on POSIX platforms. Windows support should be relatively straightforward, but was (and still is) a low priority for us. DynAsm also supports ARM. ARM64, MIPS, MIPS64 and PPC, so in theory we should be able to support all of the platforms that are popular for PHP deployments (given enough efforts).+We use DynAsm (developed for LuaJIT project) for generation of native code. It's a very lightweight and advanced tool, but does assume good, and very low-level development knowledge of target assembler languages.  In the past we tried LLVM, but its code generation speed was almost 100 times slower, making it prohibitively expensive to use. Currently we support x86 and x86_64 CPUs on POSIX platforms and Windows. DynAsm also supports ARM. ARM64, MIPS, MIPS64 and PPC, so in theory we should be able to support all of the platforms that are popular for PHP deployments (given enough efforts).
  
 PHP JIT doesn't introduce any additional IR (Intermediate Representation) form. It generates native code directly from PHP byte-code and information collected by SSA static analyses framework (a part of opcache optimizer). Code is usually generated separately for each PHP byte-code instruction. Only few combinations are considered together (e.g. compare + conditional jump). PHP JIT doesn't introduce any additional IR (Intermediate Representation) form. It generates native code directly from PHP byte-code and information collected by SSA static analyses framework (a part of opcache optimizer). Code is usually generated separately for each PHP byte-code instruction. Only few combinations are considered together (e.g. compare + conditional jump).
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 ===== State and compatibility ===== ===== State and compatibility =====
-Currently we only support x86 and x86_64 non-ZTS builds on POSIX platforms (tested on Linux). +Currently we support x86 and x86_64 on POSIX platforms (tested on Linux with GCC and LVVM) and Windows (both non-ZTS and ZTS builds). We support "Hybrid" and "Call" VM with and without GCC explicit global register variables extension. 
-We support "Hybrid" and "Call" VM with and without GCC explicit global register variables extension. +There are no any restrictions on C compiler and OS any more.
-There is no any restriction on C compiler any more. LLVM build works fine. Anatol Belski is going to work on Windows support. +
- +
-ZTS support is doable and shouldn't be very difficult, but should be implemented once the ZTS improvements described at [[https://wiki.php.net/zts-improvement|https://wiki.php.net/zts-improvement]] are done. +
- +
-Windows is not currently supported. At least 64-bit Windows implementation requires adopting to a different calling convention. +
- +
-===== Open Issues ===== +
-Make sure there are no open issues when the vote starts!+
  
 ===== Future Scope ===== ===== Future Scope =====
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 Support for JIT is more a strategic PHP question. JIT definitely requires a lot of work, but it may be actively developed only as a part of PHP, with common effort. Support for JIT is more a strategic PHP question. JIT definitely requires a lot of work, but it may be actively developed only as a part of PHP, with common effort.
  
-This project requires a 2/3+1 majority.+This project requires a 2/3+1 majority. Voting opened 2019-03-21 and closes 2019-03-28
  
 <doodle title="Include JIT into PHP 8?" auth="user" voteType="single" closed="true"> <doodle title="Include JIT into PHP 8?" auth="user" voteType="single" closed="true">
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 As PHP 7.4 is already branched and its engine is not expected to be significantly changed (consequently requiring corresponding changes to the JIT implementation), we can also consider including JIT in PHP-7.4 as an experimental feature (disabled by default), to provide early access and receive more feedback. This also requires a 2/3+1 majority. As PHP 7.4 is already branched and its engine is not expected to be significantly changed (consequently requiring corresponding changes to the JIT implementation), we can also consider including JIT in PHP-7.4 as an experimental feature (disabled by default), to provide early access and receive more feedback. This also requires a 2/3+1 majority.
 +
 +In case JIT is not included in PHP-7.4 and PHP-8 introduces language compatibility breaks (it already does), existing applications couldn't be tested with JIT without porting to PHP-8.
  
 <doodle title="Include JIT into PHP 7.4 (experimental)?" auth="user" voteType="single" closed="true"> <doodle title="Include JIT into PHP 7.4 (experimental)?" auth="user" voteType="single" closed="true">
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 ===== Implementation ===== ===== Implementation =====
-After the project is implemented, this section should contain  +Merged into PHP master by [[https://github.com/php/php-src/commit/9a06876072b9ccb023d4a14426ccb587f10882f3|9a06876072b9ccb023d4a14426ccb587f10882f3]] commit
-  - the version(s) it was merged into +
-  a link to the git commit(s) +
-  - a link to the PHP manual entry for the feature +
-  - a link to the language specification section (if any)+
  
 ===== References ===== ===== References =====
   - [[https://luajit.org/dynasm.html|DynAsm page]]   - [[https://luajit.org/dynasm.html|DynAsm page]]
   - [[https://corsix.github.io/dynasm-doc/|The Unofficial DynASM Documentation]]   - [[https://corsix.github.io/dynasm-doc/|The Unofficial DynASM Documentation]]
- 
-===== Rejected Features ===== 
-Keep this updated with features that were discussed on the mail lists. 
  
rfc/jit.txt · Last modified: 2020/08/01 23:41 by carusogabriel