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Diffstat (limited to 'skills/chapter25-codex-notes.md')
| -rw-r--r-- | skills/chapter25-codex-notes.md | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/skills/chapter25-codex-notes.md b/skills/chapter25-codex-notes.md index c409cd55..10729bf3 100644 --- a/skills/chapter25-codex-notes.md +++ b/skills/chapter25-codex-notes.md @@ -126,8 +126,25 @@ For shared viewer work, read [the graph viewer notes](graph-viewer-codex-notes.m bank, preserving integer bits when allocated to XMM. ARM's emulator needs MOVK and full MOVZ immediate/shift support. The 91-entry spill cohort changes 840 / 1,456 to 845 / 1,559; read-before-New ordering explains most of the - RISC-V BrainFuck increase. No allocator heuristics changed. Synthetic scalar - TOP exit allocation already failed before this port; see the pending queue. + RISC-V BrainFuck increase. No allocator heuristics changed in that port. + +- Synthetic never-exit TOP values remain in the graph for neutral type merges, + but have no runtime value to allocate. Chapters 20-25 exclude TOP definitions + and Phi arms from LRG construction, Phi-input liveness and spill copies; TOP + arms also do not contribute to spill loop-depth estimates. Register-bias walks + must stop at an input with no LRG. Do not give TOP a permissive register mask: + that still creates false liveness, interference and spills. Coalescing assumes + both ends of every actual copy have LRGs; fix the creation of bogus copies, + rather than adding a null guard there. + +- From Chapter 18, stop loop-tree discovery at each Return. Seed the function's + outer tree before the post-order body walk, since `forceExit` can add a return + Region and projections before the walk reaches the function entry. Those + exits inherit the function's outer tree; Never and the backedge projection + inherit the actual loop. Function bodies are depth 0, real loops add depth. + In Chapter 25, Stop/Start and StopCU/StartCU links describe external-world + type propagation, not executable loop backedges. Walking through them created + inconsistent depths and caused the RISC-V pointer-return spill-round failure. - Chapter 21's Load search is separate from the one-step factoring guard. It creates no nodes or rewiring, but records dependencies and returns folding |