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diff --git a/chapter10b/README.md b/chapter10b/README.md index c033a850..dfdf74d5 100644 --- a/chapter10b/README.md +++ b/chapter10b/README.md @@ -123,8 +123,17 @@ not to an expanded type lattice. As in Chapter 10a, diagram edges show lattice order, with top above bottom; field and tuple-element type lattices are elided. Scalar Phis remain ordinary PhiNodes. The scope's Phi factory chooses a -BulkMemPhi for whole memory; splitting constructs MemPhis explicitly. Generic -arithmetic factoring through Phis must not factor a memory aggregate. +BulkMemPhi for whole memory; splitting constructs MemPhis explicitly. Phi +factoring can combine matching Loads or Stores as in Chapter 10a, but cannot +factor MemMerge or BulkMemPhi. Its new memory operands use precise MemPhis for +the operation's alias. Load safety checks only immediate memory users, rejecting +Stores, Phis, and MemMerges. A Phi or aggregate might lead to a later write; +we conservatively skip the rewrite instead of searching farther to save one Load. + +Factoring waits while a BulkMemPhi remains at the same Region. Bulk splitting +identifies parallel slices by Region and alias, whereas factoring a Store can +introduce a memory Phi *before* the Store at that same Region. Waiting avoids +mistaking that earlier memory for the aggregate's completed slice. Memory splitting can increase node count. Progress comes from extracting an alias from a bulk Phi and simplifying its precise chain, rather than from @@ -137,7 +146,9 @@ This also extends the worklist lesson from Chapter 9. A bulk Phi inspects its users, so changes to a user's partition must wake the producer. Selecting a slice from an aggregate can expose a new bulk-Phi user; that selected definition must be queued too. The optimizer's worklist completeness assertion remains -enabled and checks these dependencies. +enabled and checks these dependencies. Factoring also depends on user counts: +removing a use wakes recorded dependents even when the definition's type stays +unchanged. ## Evaluation and ordering @@ -160,8 +171,9 @@ alias to become known later, using the same representation. Its private constructor memory, escape tracking, incomplete types, and module alias remapping are separate extensions and are not needed here. -Chapter 11 schedules this representation, including alias-specific load/store -anti-dependencies. Chapters 12-24 currently retain their older parser-managed +Chapters 11-15 use this representation, including alias-specific load/store +anti-dependencies. Chapter 15 adds allocation with partial memory and typed +alias contents. Chapters 16-24 currently retain their older parser-managed memory chains; forwarding through those snapshots is tracked in the [backport queue](../docs/chapter-backports.md). |