[review] mstan #272 - recompiler: sync GTE read-helper classification with runtime accessor semantics

[Alexbeav]

Purpose

This is a review-only retrofit for the already-open upstream PR mstan/psxrecomp#272.

Do not merge this PR. The AI reviewer must inspect this exact diff before the next upstream update.

Identity

• Upstream base: 47bda8172e43fdba1879c1a5885904a265c567f6
• Review head: 62dc9b9bb4b72bbacedada5736d783bd331e0784
• Upstream branch: pr/gte-read-classification

Review gate

Classify each finding as valid, invalid, or uncertain. A valid finding requires a correction, a regression, and repeated validation. An uncertain finding blocks the next upstream update.

Developed with AI assistance; validated as described (test evidence in PR body). AI writes the code and the PR, but I always test before I send something up. Happy to iterate on this process with your feedback.

---

Summary by cubic

Fixes the GTE read-helper classification so compiled code applies the same masking and sign-extension as the runtime accessors for data and control register reads.

• Expands data_read_needs_helper to cover regs 1, 3, 5, 7, 16-19, and ctrl_read_needs_helper to include 4, 12, 20.
• Updates the static assertion masks to match the new helper sets.

Review-only PR for upstream mstan/psxrecomp#272; do not merge.

^{Written for commit 62dc9b9. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="recompiler/include/gte_register_classification.h">

<violation number="1" location="recompiler/include/gte_register_classification.h:12">
P3: The new comments describe unsigned masked registers as sign-extended, which misstates the accessor contract. Rewrite both comments to distinguish zero-extension from sign-extension.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P3: The new comments describe unsigned masked registers as sign-extended, which misstates the accessor contract. Rewrite both comments to distinguish zero-extension from sign-extension.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At recompiler/include/gte_register_classification.h, line 12:

<comment>The new comments describe unsigned masked registers as sign-extended, which misstates the accessor contract. Rewrite both comments to distinguish zero-extension from sign-extension.</comment>

<file context>
@@ -8,7 +8,12 @@
 constexpr bool data_read_needs_helper(uint8_t reg) {
-    return (reg >= 8 && reg <= 11) || reg == 15 || reg == 23 ||
+    /* Must cover every reg gte_read_data() treats specially (gte.cpp):
+     * 1,3,5,8-11 sign-extend; 7,16-19 mask to 16 bits; 15 mirrors 14;
+     * 28/29 pack IRGB; 31 computes LZCR. 23 kept from the legacy set. */
+    return reg == 1 || reg == 3 || reg == 5 || reg == 7 ||
</file context>

[Alexbeav]

Review complete. The corresponding upstream PR was merged: mstan#272

Closing this fork review without merge. Its immutable base, discussion, and commit history remain available as evidence.