Tyson Andre
d9510342ee
Avoid the overhead of a call and checking types when the argument is definitely an array. Avoid the overhead of gc when `__destruct` won't get called. This seemed cheap enough to check for in the jit. Because of https://wiki.php.net/rfc/restrict_globals_usage we can be sure in the ZEND_COUNT handler that the array count does not have to be recomputed in php 8.1. The below example took 0.854 seconds before the optimization, and 0.564 seconds after the optimization, giving the same result ```php <?php /** @jit */ function bench_count(int $n): int { $total = 0; $arr = []; for ($i = 0; $i < $n; $i++) { $arr[] = $i; $total += count($arr); } return $total; } function main() { $n = 1000; $iterations = 50000; $start = microtime(true); $result = 0; for ($i = 0; $i < $iterations; $i++) { $result += bench_count($n); } $elapsed = microtime(true) - $start; printf("Total for n=%d, iterations=%d = %d, elapsed=%.3f\n", $n, $iterations, $result, $elapsed); } main(); ``` Before ```asm mov $0x7feb8cf8a858, %r15 mov $ZEND_COUNT_SPEC_CV_UNUSED_HANDLER, %rax call *%rax ``` After ```asm mov 0x70(%r14), %rdi - Copy the count from the `zend_array*` pointer mov %rdi, (%rax) - Store the count in the destination's value mov $0x4, 0x8(%rax) - Store IS_LONG(4) in the destination's type ``` And add tracing jit support Closes GH-5584
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.