WAFER/CHANGELOG.md

Changelog

All notable changes to WAFER are documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

0.2.9 - 2026-08-10

Fixed

• A word that never recurses no longer gets a typed entry it cannot use. Every word with a statically known stack effect was given the typed wrapper + fast-entry pair. In the JIT path the function-table slot holds the wrapper and the only caller that can reach the fast entry is RECURSE, so for any other word a cross-word call went call_indirect -> wrapper -> fast entry: one hop more for exactly the same memory traffic. On a 300k-iteration loop over a callee too big to inline that cost 1569 µs against 1067 with the convention off -- an optimisation making things worse. It is now emitted only when the body calls itself, which is where it is worth 4x (Fibonacci 242 µs typed against 636 untyped). CONSOLIDATE and the AOT export are unaffected; they solve their effects separately. Present in 0.2.7 and 0.2.8.

• The inliner's loop guard has never actually fired. 0.2.7 added a rule that a loop-bearing callee must not be inlined into a caller that can never be promoted, since the loop then loses its registers -- a 7x pessimisation applied by an optimisation pass. The check ran before inlining, where the caller is nothing but calls: DROP is Call(WordId(2)), CR is Call(WordId(38)). Since the check looks through calls by design, it called nearly every caller promotable and the guard did nothing. Inlining now happens in two passes -- loop-free callees first, then the question, then the rest.

Added

• A sixth benchmark, CrossCalls(300K), that measures what CONSOLIDATE does. The other five have no cross-word call left in their hot loop: four have their callee inlined away and Fibonacci is self-recursive. So the CONSOL column measured nothing, which is how both bugs above stayed hidden. With a real call in the loop, consolidation is worth 2.8-4x.

Changed

• The benchmark harness stops reporting noise. It took the median of three timed repetitions inside one process, and a samples field that was never read. Each measurement is now the mean of the three fastest of seven repetitions, and that whole process runs three times with the fastest kept. Benchmark noise is one-sided -- a scheduling hiccup or a busy SMT sibling can only make a run slower -- so the fastest runs are the honest ones, and only a fresh process resamples core placement and code layout. On a shared 16-vCPU box the run-to-run spread went from 20-79% to 1-6%, and Fibonacci after CONSOLIDATE stopped being bimodal (413-419 µs on three reports and 712-770 on two, with nothing in between; now 412-426 across four).

• Every benchmark is now sized to run about 10 ms, from the 0.2-2 ms most of them took. Not for the usual reason -- the timing wrapper already excludes start-up and compilation, and in the measurements shorter benchmarks were if anything the steadier ones -- but it buys a comfortable margin over timer resolution and first-iteration effects for nothing: the report still finishes in under a minute, and gforth, 3-20x slower than WAFER, is what sets that clock. Fibonacci went from 25 to 33 rather than into a loop, so it stays pure recursion; Collatz repeats its 2000-value round 50 times instead of counting higher, because past ~100000 the sequence peaks near 1.5 billion and 3 * 1+ overflows WAFER's 32-bit cells while sf64's 64-bit cells carry on -- the two engines would stop doing the same work. All three engines agree on the results at the new sizes.

Explained

• Why CONSOLIDATE makes some promoted loops slower (NestedLoops 1.7x on x86-64, 1.1x on arm64): not worse code -- the WASM is byte-identical and the machine code instruction-identical modulo registers -- but worse placement. A tight loop pays for straddling an instruction-fetch window (16 bytes on the M1 at ~9%; 32 bytes on Skylake at up to ~65%, where a fused cmp+jcc crossing the boundary drops the loop out of the uop cache every iteration -- the JCC erratum). Cranelift never aligns loop headers, and the per-word JIT module's dead dsp-prologue bytes happen to shift its loops onto luckier offsets. Verified by a padding sweep that reproduces the full penalty range on both hosts, including placements where consolidated code beats the JIT. Details in docs/OPTIMIZATIONS.md; native x86-64 reference numbers in the README re-taken at the new workload sizes.

0.2.8 - 2026-08-10

Added

• A recursive word tests its base case at the call site. A recursive Forth word almost always opens with a guard that returns early -- : FIB DUP 2 < IF EXIT THEN ... RECURSE ... ; -- so every leaf of the recursion costs a call whose entire body is that test. Call(self) now compiles as <guard> IF <what the guard returns> ELSE Call(self) THEN, which computes the same thing: the callee would have run the guard, taken the branch and returned. In fib's tree the leaves are half of all nodes.

  Fibonacci(25) 356 -> 237 µs on the arm64 development machine, where that reads 1.24x -> 0.83x of SwiftForth sf64. Measured again with both engines native on x86-64 -- the macOS sf64 build runs under Rosetta 2, which flatters WAFER -- Fibonacci is 1.16x, so it remains the one benchmark of the five that sf64 wins. See the two tables in the README.

  The guard runs twice along the recursive path, so it has to be small (at most six operations) and free of effects -- no calls, no memory, no branches. Words with more than four self-call sites are left alone to bound the code growth, and a TailCall is never expanded.

0.2.7 - 2026-08-09

Added

• A typed calling convention for words with a known stack effect. Such a word now compiles to two entry points: a fast one whose signature is (i32 x p) -> (i32 x q), carrying its stack items as WASM values, and the usual ( -- ) wrapper that moves those items on and off the memory data stack. The wrapper keeps the function-table slot, so EXECUTE, the outer interpreter, host words and CATCH see exactly the ABI they saw before; only direct calls inside a module take the fast entry.

  This is what the SwiftForth gap was made of. sf64 keeps TOS in RBX and the stack pointer in RBP, and both survive a CALL untouched, so its FIB is 16 instructions and ~7 memory touches per node. WAFER kept the whole stack in linear memory and flushed its cached $dsp to an imported global before every call: ~36 memory touches per node. The stack simulator that already promoted loop and IF bodies into WASM locals refused any body containing a call or an EXIT -- exactly the words where the convention cost the most. It now handles both.

  Fibonacci(25) goes from 1035 to 366 µs, 4.3x slower than sf64 to 1.2x. Loop-heavy benchmarks are unchanged by this entry — see the region promotion below for those. Words that keep the memory convention: anything using SP@, DEPTH, EXECUTE, >R/R>, floats or locals; anything calling a word that is itself untyped, which in the JIT path means every call except RECURSE; mutually recursive words; and words whose effect is not static -- branches that disagree on depth, EXIT at the wrong depth, a non-neutral loop body, or a recursion that grows the stack per level.

  CONSOLIDATE extends this across words, since it puts them all in one module: the effects are solved to a fixpoint from the leaves outward, and 105 of 187 words in a booted dictionary end up typed.

  Stack guards get cheap as a side effect -- they hang off the memory-stack push/pop choke points, and a typed word barely has any. The default guards-on configuration that the REPL and the web build use went from 1631 to 365 µs on the same benchmark.

  WAFER_TYPED_CALLS=0 falls back to the memory-stack convention.

• Promotion is now per region, not per word. Stack-to-local promotion used to be all-or-nothing: a single ., CR, >R or host call anywhere in a definition put the entire body on the memory data stack, hot loops included. The stack simulator now runs over each stretch of a word that can live in WASM locals, loading what the region reads and writing back what it leaves, with the rest of the word unchanged around it.

  The cliff this removes was steep. The same loop, same build:

  : L1 0 5000000 0 DO 1+ LOOP DROP ; reached as	µs	ns/iter
  its own word	1571	0.31
  inlined into a caller with a . in it (before)	11100	2.22
  the same, after this change	1572	0.31

  7x, for one i32.add: on the memory path the accumulator is stored to linear memory and reloaded next iteration, so the loop-carried dependency runs through store-to-load forwarding instead of a register.

  A region may only use I / J when the DO loops naming them are inside the region, since the simulator resolves them against its own loop stack. Straight-line regions have to be at least three operations to be worth the load and store either side; a loop always is.

• The inliner no longer drags a loop onto the memory stack. It inlined any callee of eight IR operations or fewer, so a small loop-bearing word inlined into a caller that can never be promoted lost its registers -- an optimisation pass applying the 7x pessimisation above. Loop-bearing callees now stay put in that case: one call is far cheaper than a loop's worth of memory traffic. Straight-line words still inline everywhere.

• BEGIN loops promote as well. BEGIN..UNTIL, BEGIN..AGAIN and BEGIN..WHILE..REPEAT were rejected outright by the eligibility check, so any word built on the idiomatic Forth loop kept the memory data stack no matter how hot it was. They are promoted now when the construct is stack-neutral: UNTIL consumes exactly the flag its body leaves, AGAIN's body is neutral, and for WHILE..REPEAT the test and the body balance separately -- WHILE leaves the loop between the two, so a net that only added up over the pair would give the two exits different stack shapes. Bodies containing an EXIT stay out, the same rule DO/LOOP follows. BEGIN..WHILE..WHILE..REPEAT is still excluded.

  GCD 994 -> 540 µs, Collatz 428 -> 185.

  Together these four entries put four of the five cross-engine benchmarks past SwiftForth sf64: Factorial 0.29x, Collatz 0.30x, NestedLoops 0.27x, GCD 0.67x. Fibonacci stays at 1.24x, being pure call overhead with no loop to promote.

Fixed

• A promoted loop or IF whose branch permutes the stack lost a value. At the bottom of a promoted loop the body's results are copied back into the loop-top locals, and the join after a promoted IF copies one branch's locals into the other's. Both did it one slot at a time in index order, which is wrong as soon as a destination is also a later source: : C 3 4 2 0 DO SWAP LOOP . . ; printed 4 4 where gforth and SwiftForth print 4 3, and 2 0 DO ROT LOOP over three cells printed 3 2 3 instead of 2 1 3. The copies are now ordered so every source is read before it is overwritten, with one scratch local to break a cycle. Present since stack-to-local promotion was introduced; reachable from any DO loop or IF whose body reorders cells it did not create.

• The Forth 2012 Core suite now also runs against consolidated code (compliance_core_after_consolidate). CONSOLIDATE had no correctness test at all before -- only benchmarks.

Changed

• Three cross-engine benchmarks were too small to be measured. GCD ran in 14 µs, Factorial in 49 and NestedLoops in 51, where per-run scatter is a good fraction of the total and fixed per-invocation costs in the other engines dominate. Scaled to Factorial x100K, GCD-bench(20K) and NestedLoops(50)x1K, all now around 0.5-1 ms.

  This changed a result rather than just steadying it: GCD looked like a win at 0.42x of sf64 and was in fact a loss at 1.17x. That is what pointed at BEGIN loops as the remaining gap -- GCD is the one benchmark whose loop is a BEGIN ... WHILE ... REPEAT -- and with those promoted it now reads 0.67x. The regression limits, which had drifted to 3-6x looser than the measurements they guard, were retightened to ~45% above the current ratios.

[0.2.6] - 2026-08-07

Fixed

• An uncaught ABORT no longer prints anything. It used to report ABORT (throw -1), but the standard defines ABORT as "empty the data stack and perform the function of QUIT", and QUIT displays no message. gforth and SwiftForth are both silent here. CATCH still reports -1 as before, and ABORT" still prints its text — that is a different word with a different code (-2).
• Compile-only words used in interpretation state name the condition. ABORT", IF, THEN, LOOP, LITERAL, RECURSE and the rest of the compile-time constructs claimed to be an unknown word, which is actively misleading for a word the system obviously knows. They now report interpreting a compile-only word: <name> (throw -14), the standard condition both reference engines give. A genuine typo still reports unknown word.

[0.2.5] - 2026-08-06

Added

• QUIT ( -- ) ( R: i*x -- ), the CORE word that was missing: empty the return stack, enter interpretation state, hand the input source back to the user input device and return to the interpreter without a message. The data stack is deliberately left alone — that is the whole difference to ABORT, which the standard defines as "empty the data stack, then QUIT". It unwinds through nested EVALUATE and INCLUDE, abandoning them, and SOURCE-ID is restored to 0.

  CATCH does not report it: QUIT rides throw code -56, which the interpreter treats as a return to the prompt rather than an exception. Both behaviours were checked against gforth 0.7.3 and SwiftForth sf64, which agree — 1 2 ' QUIT CATCH . prints nothing and leaves 1 2 on the stack in all three engines.

  The gap had gone unnoticed because the Forth 2012 test suite skips it by its own admission ("I HAVEN'T FIGURED OUT HOW TO TEST KEY, QUIT, ABORT, OR ABORT""), and because HELP's coverage lint compares the dictionary against the docs — a word absent from both looks complete. docs/wafer-anki.txt had been documenting QUIT as if it existed.

  Note that ABORT was already correct: executing it while a definition is open does clear both stacks and return to interpretation state. Typing ABORT (or QUIT) into an unfinished definition compiles it rather than running it, exactly as in every other Forth; [ is the word that gets you out.

[0.2.4] - 2026-08-06

Fixed

• Errors from host words in the browser build read like Forth errors again. A host word signals failure by throwing across the JS boundary, and the browser runtime reported the exception with its Debug form, so an empty-stack RESIZE came back as call_func(134) failed: JsValue(Error: Stack underflow ...) trailed by an engine stack trace. The thrown message is the Forth message, so it is now surfaced verbatim — Stack underflow, exactly what the native CLI prints. Exceptions that carry no message keep the call context, since those are genuine runtime faults rather than Forth throws. CATCH was never affected: it reads the throw code from its own channel, not from the message.

[0.2.3] - 2026-08-06

Fixed

• Release builds of wafer-web no longer fail on proc-macro loading. Cargo strips debuginfo from release artifacts by default, and on macOS that also strips the metadata proc-macro dylibs need to be loadable, so wasm-pack build --release died with can't find crate for rustversion, thiserror_impl and every other proc-macro. Build scripts and proc-macros gain nothing from stripping, so [profile.release.build-override] now exempts them; release binaries stay stripped. Debug builds were never affected, which is why the test suite stayed green while the browser REPL could not be built for production.
• wafer-web and wafer-cli requested wafer-core version 0.2.1 while the workspace had moved to 0.2.2. The caret requirement still resolved, so nothing broke, but the pin is now kept in step.

[0.2.2] - 2026-08-06

Added

• SwiftForth-style input number conversion. Punctuation (, . + / : and an embedded -) anywhere after the leftmost digit now forces double-cell conversion, so 12.34, 1,234, 12:30:45 and 2026-08-06 all convert as doubles without a custom parser. Previously only a trailing . worked and 1.5 was an "unknown word" error. The punctuation is a double-cell marker, not a fractional point: every spelling of 1234 (1234., 123.4, .1234) yields the same value.
• DPL ( -- addr ): digits to the right of the rightmost punctuation character in the last converted number, negative when the token carried none. Seeded at -1024 and bumped once per digit, matching sf64. Together with <# #> this is how fixed-point input is scaled.
• NH ( -- addr ): the high-order cell dropped by a single-cell conversion, so a token that overflows a cell can be recovered as a double (4000000000 NH @ D.).

Verified token-for-token against SwiftForth sf64: DPL values, double promotion and sign handling agree on every probed form. One deliberate divergence — WAFER also accepts a sign before a base prefix (-$FF), which sf64 rejects; the Forth 2012 spelling $-FF works in both. A leading + is punctuation rather than a sign in both engines, so +7 is the double 7 with DPL = 1.

0.2.1 - 2026-08-06

Fixed

• The search order is now authoritative (Forth 2012 §16.3.3): a word whose wordlist is not in the search order is no longer findable. Previously lookup fell back to the newest entry across all wordlists, making word hiding impossible. Verified against gforth and SwiftForth, and guarded by a cross-engine corpus program.
• Host words validate their stack arguments. Around 40 host-implemented words (RND-SEED, ACCEPT, RESIZE, ALLOCATE, FREE, SEARCH, SUBSTITUTE, ROLL, M*, UM/MOD, SF@ SF! DF@ DF!, F. FE. FS. F~, 2R@, and friends) performed raw stack-pointer arithmetic with no underflow check — calling them on an empty stack silently corrupted the stack pointer (the compiled-code guards from 0.2.0 do not cover host words). All argument-taking host words now fail with a clean, CATCHable underflow error, enforced by a class-wide regression test.

0.2.0 - 2026-08-06

The usability release: introspection, source files, honest errors, and a safety net under every compiled word.

Added

• Stack guards in compiled code: under/overflow checks at the stack-pointer choke points of generated WASM. Faults THROW standard codes (-3..-6, -44, -45), are CATCHable, and print standard messages instead of silently corrupting memory. Default on; wafer build output stays unguarded; WAFER_STACK_GUARDS=0|1 overrides.
• SEE: source-level decompiler. Colon words (including everything in boot.fth) show their captured verbatim source; data words show synthesized definitions with current values (9 VALUE X, DEFER D ( IS DUP )); primitives fall back to a readable IR dump — SEE never dead-ends on a defined word.
• SEE-IR: post-optimization IR view with resolved callee names and indented control flow — shows what the optimizer actually did.
• HELP: stack effect + one-line description for every word in a fresh VM (dictionary words and outer-interpreter tokens alike); coverage is enforced by a unit test, so an undocumented new word fails the build. User words echo their leading ( n -- n ) comment.
• INCLUDE / INCLUDED: nestable source-file loading with cycle detection, depth bound, paths relative to the including file, and per-level SOURCE-ID. The loader is injected (CLI: filesystem; web: defined error), so the core stays IO-free. wafer prog.fth now runs through the same machinery.
• MARKER extensions: REMEMBER (re-runnable marker), EMPTY and GILD (boot-state rollback and re-baselining). Marker rollback now also restores search order, wordlists, REPLACES substitutions, ABORT" texts, and captured word sources — enabling the REMEMBER + INCLUDE edit-reload loop.
• WORDS: optional substring filter (WORDS FLOAT), word count, and WORDS ALL — a grouped full view by wordlist plus internal words.
• Return-stack introspection: .RS, RDEPTH, RP@.
• Tools: .S honors BASE, F.S, ?, bounds-checked DUMP, real BYE, named ORDER output.
• CLI REPL: persistent history (XDG state dir, 0600), dictionary-backed tab completion, prefix history search on Up/Down, Ctrl-C clears the line.
• Web REPL: history persisted to localStorage, User Words palette, BASE indicator in the stack bar.
• Error reporting: uncaught THROW codes map to standard messages; ABORT" text prints only when uncaught; errors inside included files carry file.fth:line: context; uncaught throws are typed (WaferError::UncaughtThrow) for embedding consumers; compiled words carry WASM name sections, so genuine traps name the faulting word (in CRASHER: wasm trap: out of bounds memory access).
• SwiftForth correctness lane: the cross-engine program corpus can run against sf64 as an oracle (just compare-correctness), alongside the existing gforth lane and the sf64 performance lane.

Fixed

• Multi-line command output in the CLI REPL starts on its own line (inline ok echo only for single-line output).
• .S printed in decimal regardless of BASE.
• A bare interpreted R> underflowed silently (exposed by the new stack guards; compliance baseline updated).
• SPACES with a negative count now outputs nothing, per Forth 2012 6.1.2230.

Changed

• wafer prog.fth reports errors with file:line context and resolves nested INCLUDEs relative to the file.
• Internal words (_-prefixed) are flagged in the dictionary and hidden from WORDS and completion (WORDS ALL shows them).
• Dependencies upgraded across the board: wasmtime 43 → 47, wasm-encoder/wasmparser 0.246 → 0.255, plus all semver-compatible updates.

0.1.0 - 2026-08-04

Initial development line (untagged): Forth 2012 core with IR optimizer and WASM codegen via wasm-encoder/wasmtime, ~300 words across Core, Double, Float, String, Search-Order, Exception, and Tools word sets, Forth 2012 compliance suite, CONSOLIDATE whole-program recompilation, wafer build AOT export (WASM / native / JS loader), browser REPL, SHA-1/256/512 words, and cross-engine benchmark lanes against gforth and SwiftForth.