Fixing uninitialized memory access in fast memcpy.

[nicolasnoble]

The $a3 register was uninitialized in the unaligned case.

[coderabbitai]

Walkthrough

The update modifies the unaligned memcpy routine in the MIPS assembly startup code by introducing instructions to calculate the end pointer for 32-byte chunk copying. This aligns the unaligned code path with the calculation already present in the aligned path, ensuring consistent loop boundaries. No other logic or exported entities are changed.

Changes

File(s)	Change Summary
src/mips/common/crt0/memory-s.s	Added instructions to compute the 32-byte chunk copy end pointer in the unaligned memcpy code path.

Poem

In memory’s warren, bytes must hop,
Unaligned or straight, they never stop.
A pointer now knows where to end,
Thirty-two steps, around the bend!
With careful math, the loops align,
Assembly rabbits—code divine. 🐇

---

📜 Recent review details

Configuration used: .coderabbit.yaml
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 15e839b and 8410616.

📒 Files selected for processing (1)

• src/mips/common/crt0/memory-s.s (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (13)

• GitHub Check: pcsx-redux (x86_64-linux)
• GitHub Check: pcsx-redux (aarch64-linux)
• GitHub Check: pcsx-redux (x86_64-linux)
• GitHub Check: pcsx-redux (aarch64-linux)
• GitHub Check: Codacy Static Code Analysis
• GitHub Check: build-openbios
• GitHub Check: toolchain
• GitHub Check: asan
• GitHub Check: cross-arm64
• GitHub Check: aur-build
• GitHub Check: coverage
• GitHub Check: macos-build-and-test-toolchain
• GitHub Check: build

🔇 Additional comments (1)

src/mips/common/crt0/memory-s.s (1)

132-134: Properly initialize $a3 in unaligned memcpy path
These two instructions mirror the aligned-path setup by computing $a3 = $a1 + $a2 – 32 before entering .Lmemcpy_loop32_unaligned. This prevents uninitialized‐register use and bounds the 32‐byte copy loop correctly.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

🪧 Tips

Chat

There are 3 ways to chat with CodeRabbit:

• Review comments: Directly reply to a review comment made by CodeRabbit. Example:
  • I pushed a fix in commit <commit_id>, please review it.
  • Explain this complex logic.
  • Open a follow-up GitHub issue for this discussion.
• Files and specific lines of code (under the "Files changed" tab): Tag @coderabbitai in a new review comment at the desired location with your query. Examples:
  • @coderabbitai explain this code block.
  • @coderabbitai modularize this function.
• PR comments: Tag @coderabbitai in a new PR comment to ask questions about the PR branch. For the best results, please provide a very specific query, as very limited context is provided in this mode. Examples:
  • @coderabbitai gather interesting stats about this repository and render them as a table. Additionally, render a pie chart showing the language distribution in the codebase.
  • @coderabbitai read src/utils.ts and explain its main purpose.
  • @coderabbitai read the files in the src/scheduler package and generate a class diagram using mermaid and a README in the markdown format.
  • @coderabbitai help me debug CodeRabbit configuration file.

Support

Need help? Create a ticket on our support page for assistance with any issues or questions.

Note: Be mindful of the bot's finite context window. It's strongly recommended to break down tasks such as reading entire modules into smaller chunks. For a focused discussion, use review comments to chat about specific files and their changes, instead of using the PR comments.

CodeRabbit Commands (Invoked using PR comments)

• @coderabbitai pause to pause the reviews on a PR.
• @coderabbitai resume to resume the paused reviews.
• @coderabbitai review to trigger an incremental review. This is useful when automatic reviews are disabled for the repository.
• @coderabbitai full review to do a full review from scratch and review all the files again.
• @coderabbitai summary to regenerate the summary of the PR.
• @coderabbitai generate docstrings to generate docstrings for this PR.
• @coderabbitai generate sequence diagram to generate a sequence diagram of the changes in this PR.
• @coderabbitai resolve resolve all the CodeRabbit review comments.
• @coderabbitai configuration to show the current CodeRabbit configuration for the repository.
• @coderabbitai help to get help.

Other keywords and placeholders

• Add @coderabbitai ignore anywhere in the PR description to prevent this PR from being reviewed.
• Add @coderabbitai summary to generate the high-level summary at a specific location in the PR description.
• Add @coderabbitai anywhere in the PR title to generate the title automatically.

Documentation and Community

• Visit our Documentation for detailed information on how to use CodeRabbit.
• Join our Discord Community to get help, request features, and share feedback.
• Follow us on X/Twitter for updates and announcements.