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perf(core): test a recursive word's base case at the call site
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A recursive Forth word almost always opens with a guard that returns early,
so every leaf of the recursion costs a call whose whole body is that test.
`Call(self)` now compiles as `<guard> IF <what the guard returns> ELSE
Call(self) THEN`, which is what the callee would have done on entry anyway.
Half of fib's nodes are leaves: Fibonacci(25) 356 -> 237 us, 1.24x sf64 ->
0.83x, so all five benchmarks now beat it.

The guard runs twice along the recursive path, hence the bounds: at most six
effect-free operations, at most four call sites, never a tail call. WS-018.
This commit is contained in:
Oleksandr Kozachuk
2026-08-09 18:27:25 +02:00
parent 645c2dadd7
commit e963e636d3
8 changed files with 394 additions and 37 deletions
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CLAUDE.md
+2 -2
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@@ -2,7 +2,7 @@
## What is WAFER?
WAFER (WebAssembly Forth Engine in Rust) is an optimizing Forth 2012 compiler targeting WebAssembly. Currently a working Forth system with 200+ words, JIT compilation, 12 word sets at 100% compliance, and a full optimization pipeline (peephole, constant folding, inlining, strength reduction, DCE, tail calls, per-region stack-to-local promotion with DO/BEGIN loop and IF support, self-recursive direct calls, a typed calling convention for words with a known stack effect, consolidation). Beats gforth on all benchmarks in release mode, and SwiftForth `sf64` on four of five. Includes a browser-based REPL via wasm-pack.
WAFER (WebAssembly Forth Engine in Rust) is an optimizing Forth 2012 compiler targeting WebAssembly. Currently a working Forth system with 200+ words, JIT compilation, 12 word sets at 100% compliance, and a full optimization pipeline (peephole, constant folding, inlining, strength reduction, DCE, tail calls, per-region stack-to-local promotion with DO/BEGIN loop and IF support, self-recursive direct calls, a typed calling convention for words with a known stack effect, self-guard expansion for recursive words, consolidation). Beats gforth on all benchmarks in release mode (3-20x), and SwiftForth `sf64` on all five. Includes a browser-based REPL via wasm-pack.
## Architecture
@@ -79,7 +79,7 @@ Handle in `interpret_token_immediate()` or `compile_token()` as a special case.
## Testing
- Run `cargo test --workspace` before committing (currently 601 unit + 1 benchmark + 12 compliance + 9 comparison + 5 crypto)
- Run `cargo test --workspace` before committing (currently 608 unit + 1 benchmark + 12 compliance + 9 comparison + 5 crypto)
- Forth 2012 compliance: `cargo test -p wafer-core --test compliance`
- Cross-engine comparison (vs gforth): `cargo test -p wafer-core --test comparison`
- Performance benchmarks (release mode): `cargo test -p wafer-core --test comparison -- --nocapture --ignored`