LLVM-DIFF(1)

💖 NAME 💖

This is the LLVM-DIFF(1) page from the LLVM manual, bestie — and it's all about llvm-diff, the LLVM structural 'diff'. It's giving “compare the vibes of two modules” energy. 💅✨

🌸 SYNOPSIS 🌸

llvm-diff [options] module 1 module 2 [global name ...]

🦋 DESCRIPTION 🦋

Okay so llvm-diff compares the structure of two LLVM modules, and it's primarily focusing on differences in function definitions. Insignificant differences, like changes in the ordering of globals or in the names of local values, are literally ignored. No cap. 🫶

An input module will be interpreted as an assembly file if its name ends in .ll; otherwise it will be read in as a bitcode file. Important detail, bestie. 🌟

If a list of global names is given, just the values with those names are compared; otherwise, all global values are compared, and diagnostics are produced for globals which only appear in one module or the other. Slay, that's the scope. 💖

llvm-diff compares two functions by comparing their basic blocks, beginning with the entry blocks. If the terminators seem to match, then the corresponding successors are compared; otherwise they are ignored.

⚠️ This algorithm is very sensitive to changes in control flow, which tend to stop any downstream changes from being detected. So yeah, control-flow changes can absolutely eat your downstream diff results. 😭

llvm-diff is intended as a debugging tool for writers of LLVM passes and frontends. It does not have a stable output format. Periodt. 💅

🌈 EXIT STATUS 🌈

• If llvm-diff finds no differences between the modules, it will exit with 0 and produce no output. Clean. ✨
• Otherwise it will exit with a non-zero value. Not clean, but useful. 💀

💀 BUGS 💀

• Many important differences, like changes in linkage or function attributes, are not diagnosed. Iconic but unfortunate. 🙈
• Changes in memory behavior (for example, coalescing loads) can cause massive detected differences in blocks. It's giving “the diff said what now?” energy. 😭

👑 AUTHOR 👑

Maintained by the LLVM Team (https://llvm.org/). Crown them. 👑

🎀 COPYRIGHT 🎀

2003-2023, LLVM Project. Respect the copyright era, bestie. 🎀

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This iconic page comes from the LLVM source/version and is dated 2023-01-14 — bye bestie, go diff those modules! 💖🦋