D113 - Translations cached by content

Status: assumed Date: 2026-09-26

The translation cache is keyed by a hash of the shader's decoded extent: decode, hash, look up, translate. A hit re-checks the length and both end words, and a mismatch is refused. The cache is stored per title in the title library. Each entry records the shader's bytes and what it was translated against beside the module, so a later run serves the module without translating, and before the guest starts every entry another translator made is translated again from its recorded shader. A draw finds its translation already made. The translator is named by the build and a digest of its sources and tables taken at build time, so a build from an edited tree is another translator though it names the same commit.

Why: a guest moves shaders, reuses addresses and holds one shader at two addresses. An address-keyed cache serves the old translation for a new shader and nothing indicates it. A content key is also stable across runs, which is what lets translation happen ahead of the first draw.

Rejected:

• Keying by address: stale hits drawn with code the guest has replaced.
• Keying by the read window: identical shaders followed by different data never hit.