b3e28e2290
Commit a21195650e fixed a leak by adding a TSRM destructor for the
JIT globals in ZTS mode. In case the main thread shuts down the TSRM, it
will call all the destructors. The JIT globals destructor will be
invoked, but will always access the main thread globals using JIT_G.
This means that instead of freeing the JIT globals in the different
threads, the one in the main thread is freed repeatedly over and over,
crashing PHP. Fix it by always passing the pointer instead of relying on
JIT_G.
Closes GH-10835.
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.