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| -rw-r--r-- | docs/chapter-backports.md | 107 |
1 files changed, 99 insertions, 8 deletions
diff --git a/docs/chapter-backports.md b/docs/chapter-backports.md index ebb75056..d7674559 100644 --- a/docs/chapter-backports.md +++ b/docs/chapter-backports.md @@ -22,15 +22,50 @@ Splitting Chapter 25 is deferred, not an instruction to renumber. ## Pending corrections -- **Forward Chapter 10b memory partitioning through 12-24; review 11 first.** The 10a/10b split +- **Forward Chapter 10b memory partitioning through 16-24.** The 10a/10b split introduces whole-memory SSA first, then `MemMerge`, `MemPhi`, and `BulkMemPhi`. - Chapter 11 is implemented and tested, awaiting Cliff's requested review at - the first significant adaptation: scheduling aggregates and alias-filtered - anti-dependencies. Do not continue to 12 before that review. Later snapshots - retain their original memory representation. Further migration - boundaries include array/allocation memory in 15, the - parser's `ScopeMinNode` in 16, and call/return aggregation in 18. Keep private - constructor memory, escape tracking, and incomplete-type inference in 25. + Cliff reviewed and committed Chapter 11 as `b475b072`. Chapters 12-15 are + implemented and tested. Chapter 15's approved allocation design is now ready + for implementation review; stop here before proceeding to 16. Subsequent + boundaries include the parser's `ScopeMinNode` in 16 and call/return + aggregation in 18. Keep private constructor memory, escape tracking, and + incomplete-type inference in 25. + Carry the generalized Phi factoring and its dependency fixes from 10a-15 + with the next ports; later snapshots already have parts of that rewrite. + +### Chapter 15 allocation design (implemented) + +Chapters 12-14 retain explicit initialization Stores. Chapter 15 replaces them +with New's zeroing operation while keeping one parser-visible `$mem`. + +| Interface | Chapter 15 | +|---|---| +| New inputs | `{ctrl, $mem, size}` | +| New outputs | `{ptr, $mem}`; no control result or per-alias projections | +| Coverage | field aliases from New's internal TypeStruct/TypeMemPtr | +| Input memory | partial MemMerge, no default, entries for affected aliases | +| Result integration | whole-memory MemMerge, prior default, affected entries all using the same New memory projection | +| Memory types | existing alias plus stored-value type; no lattice extension | + +A null MemMerge default means absent aliases are uncovered. Empty structs +therefore have an empty partial input; their allocation does not change the +whole-memory aggregate. New's output also covers only its own aliases. + +An alias-specific contents query combines incoming values with the field's +initializer from New's struct (integer zero, floating zero, or null). It records +optimizer dependencies and stops at cached Phi types to break loops. MemPhi +merges the scalar contents of its precise alias. Start's incoming heap is empty +in this chapter; functions with heap arguments will require a different entry +query in Chapter 18. + +Loads fold against their own New and bypass a proven distinct allocation via +New's memory input. Different pointer nodes alone do not establish disjointness. +Array length remains a subsequent Store; array access control inputs remain. +Global code motion and the evaluator scheduler both follow an alias through +MemMerge to discover the allocation's ordering constraint. MemMerge is packaging, +not itself a clobber. The viewer and evaluator use the new slot conventions. + +### Other pending corrections - **Chapter 24 Load BOTTOM-on-error backport, unwound/deferred (2026-09-28).** Cliff requested starting with 24 and analyzing failures before proceeding. @@ -220,6 +255,62 @@ The top-level runner accepts explicit chapter lists, e.g. ## Validation record +- **Generalized Phi factoring, 10a through 15.** Replaced binary-only factoring + and the blanket memory exclusion with operand-wise Phis and exact-class + `copyEmpty`. Matching Loads and sole-use Stores are eligible when unbound to + control; operation attributes, field/alias identity, operand types, and + result-type monotonicity are preserved. Load safety examines memory users + before explicit GCM anti-dependencies exist. The final guard checks only + immediate users, stopping at Stores, Phis, MemMerges, and New in 15. Memory factoring waits for bulk + partitioning at its Region; MemMerge and BulkMemPhi are never factored. + Stores bound to control in 11-14 remain excluded. User removal now wakes + recorded dependents, and empty-diamond folding observes projection rewiring. + Three regressions live in each snapshot's `Chapter10Test`; the original 10a + Phi fails both positive folding checks, and disabling the Load safety guard + exposes an invalid read/write schedule in the negative probe. + Full Make tests pass **159 / 162 / 177 / 181 / 196 / 216 / 230** and all seven + release jars build. A 10a Phi label and one 14 Region ID were refreshed; + expression/value expectations remain unchanged. Each snapshot also passes + **3,500 evaluations across 100 optimizer seeds**, and 15 passes another + **7,000 allocation/memory evaluations**. Logs: `build/phi-drop-baseline.log`, + `build/phi-drop-tests.log`, `build/phi-drop-seeds*.log`, + `build/phi-drop-negative.log`, `build/phi-drop-antidep-negative.log`, and + `build/phi-drop-allocation-seeds15.log`. Chapters 16+ are unchanged. + The subsequent guard refactor moves memory eligibility into virtual + `MemOpNode.canDrop` overrides and clobber inspection into Load. Removed 10a's + unused visited set. All 1,321 tests and seven release builds passed + (`build/phi-guards-refactor.log`). At Cliff's request, the subsequent + simplification also removes recursive aggregate traversal from 10b-15: + a one-step check conservatively stops at possible indirect clobbers, + keeping the teaching cost proportionate to saving one Load. The aggregate + example now keeps two Loads in 10b-15; its runtime checks remain unchanged. + All 1,321 tests and seven release builds pass with the simpler guard + (`build/phi-guards-one-step.log`). + +- **Chapter 15 partial allocation memory (review checkpoint).** Implemented the + approved two-result New and carried the lazy memory model through parser, + scheduling, evaluator, viewer roles, and chapter documentation. Full Make + suite passes **227 tests** and the release jar builds, up from baseline **218**: six carried memory + regressions plus three allocation regressions. They cover unrelated aliases, + mixed integer/float/pointer contents, reads across allocation, and allocation + inside loops. A disposable probe also passed **7,000 evaluations across 100 + optimizer seeds**, including empty structs, arrays, both slot conventions, + partial coverage, and complete scheduling of live definitions. Region/Loop + golden changes only alter IDs; the nullable-access diagnostic matches 13-14. + Logs: `build/memory15-baseline.log`, `build/memory-forward-15.log`, and + `build/memory15-seeds.log`; final tests and release: `build/memory15-final.log`. + +- **Memory forward port through Chapters 12-14.** Preserved + floating-point operations, typed reference initialization, and narrow stores + while forwarding the reviewed parser, memory nodes, GCM, Return slots, and + evaluator. Each chapter inherits all six memory regressions. Make tests pass + **178 / 193 / 213**, up from baselines **172 / 187 / 207**; all three release + jars build. Updated printed Region/Loop IDs without changing expression + expectations. The invalid `head.next.i` test in 13 and 14 now reports the + possibly-null `i` access first; both accesses remain invalid, and the test + still requires rejection. Logs: `build/memory-forward-baselines.log` and + `build/memory-forward-12-14.log`. The subsequent allocation port is recorded above. + - **Control/memory slot convention (10a, 10b, 11).** Return now takes `{ctrl, $mem, result}` and describes its result tuple in that order, with whole memory typed as `TypeMem.BOT`. Evaluators use `expr()` rather than a |