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From an engine perspective, named parameters mainly add three concepts: * The SEND_* opcodes now accept a CONST op2, which is the argument name. For now, it is looked up by linear scan and runtime cached. * This may leave UNDEF arguments on the stack. To avoid having to deal with them in other places, a CHECK_UNDEF_ARGS opcode is used to either replace them with defaults, or error. * For variadic functions, EX(extra_named_params) are collected and need to be freed based on ZEND_CALL_HAS_EXTRA_NAMED_PARAMS. RFC: https://wiki.php.net/rfc/named_params Closes GH-5357.
Opcache JIT
This is the implementation of Opcache's JIT (Just-In-Time compiler), This converts the PHP Virtual Machine's opcodes into x64/x86 assembly, on POSIX platforms and Windows.
It generates native code directly from PHP byte-code and information collected by the SSA static analysis framework (a part of the opcache optimizer). Code is usually generated separately for each PHP byte-code instruction. Only a few combinations are considered together (e.g. compare + conditional jump).
See the JIT RFC for more details.
DynAsm
This uses DynAsm (developed for LuaJIT project) for the 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.
The unofficial DynASM Documentation has a tutorial, reference, and instruction listing.
zend_jit_x86.dasc gets automatically converted to zend_jit_x86.c by the bundled
dynasm during make.