[llvm] [GitHub] Add Copilot review instructions for LLDB (PR #165783)

[Jonas Devlieghere via llvm-commits]

https://github.com/JDevlieghere created https://github.com/llvm/llvm-project/pull/165783

This is an experiment to encode the LLVM Coding Standards [1] as instructions for the Copilot reviewer on GitHub. Ideally, this will catch common issues automatically and reduce the review burden.

Adding Copilot as a reviewer is entirely opt-in. Initially, I will add it as a reviewer to test this. If the experiment is successful, we can explore how to integrate this into other parts of LLVM.

[1]: https://llvm.org/docs/CodingStandards.html

>From cdca339ac2b4c65673e52ddbbecd439aa65cba54 Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas at devlieghere.com>
Date: Thu, 30 Oct 2025 14:30:17 -0700
Subject: [PATCH] [GitHub] Add Copilot review instructions for LLDB

This is an experiment to encode the LLVM Coding Standards [1] as
instructions for the Copilot reviewer on GitHub. Ideally, this will
catch common issues automatically and reduce the review burden.

Adding Copilot as a reviewer is entirely opt-in. Initially, I will add
it as a reviewer to test this. If the experiment is successful, we can
explore how to integrate this into other parts of LLVM.

[1]: https://llvm.org/docs/CodingStandards.html
---
 .github/instructions/lldb.instructions.md | 76 +++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 .github/instructions/lldb.instructions.md

diff --git a/.github/instructions/lldb.instructions.md b/.github/instructions/lldb.instructions.md
new file mode 100644
index 0000000000000..450b02ba009c0
--- /dev/null
+++ b/.github/instructions/lldb.instructions.md
@@ -0,0 +1,76 @@
+---
+applyTo: lldb/**/*
+---
+
+When reviewing code, focus on:
+
+## Language, Libraries & Standards
+
+- Target C++17 and avoids vendor-specific extensions.
+- For Python scripts, follow PEP 8 formatting and use tools like `black` or `darker`.
+- Prefer standard library or LLVM support libraries instead of reinventing data structures.
+
+## Comments & Documentation
+
+- Each source file should include the standard LLVM file header.
+- Header files must have proper header guards.
+- Non-trivial classes and public methods should have Doxygen documentation.
+- Use `//` or `///` comments normally; avoid block comments unless necessary.
+
+## Language & Compiler Issues
+
+- Write portable code; wrap non-portable code in interfaces.
+- Do not use RTTI or exceptions.
+- Prefer C++-style casts over C-style casts.
+- Avoid static constructors or global objects with heavy initialization.
+- Use `class` or `struct` consistently; `struct` only for all-public data.
+
+## Headers & Library Layering
+
+- Include order: module header → local/private headers → project headers → system headers.
+- Headers must compile standalone (include all dependencies).
+- Maintain proper library layering; avoid circular dependencies.
+- Include minimally; use forward declarations where possible.
+- Keep internal headers private to modules.
+- Use full namespace qualifiers for out-of-line definitions.
+
+## Control Flow & Structure
+
+- Prefer early exits over deep nesting.
+- Avoid `else` after `return`, `continue`, `break`, or `goto`.
+- Encapsulate loops that compute predicates into helper functions.
+
+## Naming
+
+- LLDB's code style differs from LLVM's coding style.
+- Variables are `snake_case`.
+- Functions and methods are `UpperCamelCase`.
+- Static, global and member variables have `s_`, `g_` and `m_` prefixes respectively.
+
+## General Guidelines
+
+- Use `assert` liberally; prefer `llvm_unreachable` for unreachable states.
+- Avoid `using namespace std;` in headers.
+- Ensure at least one out-of-line virtual method per class with virtuals.
+- For `switch` on enums, omit `default` to catch missing cases.
+- Prefer range-based `for` loops.
+- Capture `end()` outside loops if not using range-based iteration.
+- Use LLVM’s `raw_ostream` instead of `<iostream>`.
+- Avoid `std::endl`; use `\n` unless flushing is needed.
+- Methods in class definitions are already inline—don’t add `inline`.
+
+## Microscopic Details
+
+- Preserve existing style in modified code.
+- Prefer pre-increment (`++i`) when value is unused.
+- Omit braces for single-statement `if`, `else`, `while`, `for` unless needed.
+
+## Review Style
+
+- Be specific and actionable in feedback.
+- Explain the "why" behind recommendations.
+- Link back to the LLVM Coding Standars: https://llvm.org/docs/CodingStandards.html.
+- Ask clarifying questions when code intent is unclear.
+
+Remember that these standards are **guidelines**. Always prioritize consistency
+with the style that is already being used by the surrounding code.