$ show dstogov/ir
This is a lightweight JIT (Just-In-Time) compilation framework named 'IR', authored by Dmitry Stogov (a core PHP developer). It provides a complete pipeline for translating a custom intermediate representation (SSA-based sea-of-nodes) into native machine code for x86, x86_64, and AArch64 architectures. The framework includes a rich set of optimization passes: constant folding with a perfect-hash-based pattern matcher, sparse conditional constant propagation (SCCP), global code motion (GCM), memory-to-SSA conversion, and linear scan register allocation. It also supports alternative backends: C code generation and LLVM IR emission. The IR is used in production as the JIT engine for PHP since PHP 8.4 and as a backend for the Rational C Compiler. The codebase is highly modular, with a clear separation between the IR representation, optimization passes, target-specific code generation (via DynASM templates), and debugging/profiling support (GDB JIT integration, Linux perf, capstone disassembly). The framework is designed for embedding into larger runtimes, offering a C API for IR construction and compilation. The repository includes extensive test suites (over 1000 .irt files), fuzz harnesses, and a CI pipeline that builds and tests on Linux, macOS, FreeBSD, and Windows. The architecture follows academic compiler research (Cliff Click, Wegman & Zadeck, Wimmer & Franz) and borrows ideas from LuaJIT's IR. The code is actively maintained, with recent commits, but some features are marked as not yet implemented, reflecting its ongoing development.
The LLM identified 3 files worth highlighting for reuse:
DynASM is a Lua-based dynamic assembler framework that generates machine code at runtime. The `dasm_x86.lua` module implements the x86/x64 instruction encoding logic, including opcode tables, register maps, address mode handling, and label management. It is used by the IR project to emit native code via action lists that are processed by the C runtime (`dasm_proto.h`). This module is highly reusable: it can be extracted and used in any JIT compiler or runtime that needs to generate x86/x64 machine code. The pattern demonstrates non-obvious skill in combining a scripting language (Lua) with a C runtime to produce a compact, retargetable assembler, inspired by LuaJIT's DynASM.
This header defines hundreds of declarative constant folding and algebraic simplification rules for the IR. Each rule is written as a macro using a DSL that captures the operation, input types, and the resulting expression. The rules are processed by `gen_ir_fold_hash.c` to generate a perfect hash table for efficient pattern matching at compile time. The pattern is self-contained, requires only knowledge of the IR opcodes, and can be adapted to any IR or expression language. It demonstrates advanced compiler engineering: using a code generator to transform high-level rewrite rules into a fast, collision-free dispatch table. This component is a textbook example of how to implement a folding engine with minimal runtime overhead.
A simple, efficient string interning table implementation. It provides `ir_string()` and `ir_stringl()` to insert strings into a global hash table, returning unique identifiers. The implementation uses open addressing with linear probing, automatic resizing, and memory-mapped allocation. It is completely self-contained, depends only on the core `ir.h` types, and can be extracted into any project that needs string deduplication. The design is clean and idiomatic, with a focus on performance (no dynamic allocations for small strings, precomputed hash). This is a classic reusable data structure pattern, well-suited for compilers, interpreters, or any system that manipulates many symbolic names.