Inspecting the emitted Wasm

This folder is the smallest possible AssemblyScript wrapper around the two SWAR detectors so you can compare the emitted Wasm directly.

Compile to Wasm and WAT

From the json-as repo root:

cat > ./build/swar-detect-inspect.ts <<'EOF'
import {
  detect_escapable_u64_swar_safe,
  detect_escapable_u64_swar_unsafe,
} from "../assembly/serialize/swar/string";

export function safe(block: u64): u64 {
  return detect_escapable_u64_swar_safe(block);
}

export function unsafe(block: u64): u64 {
  return detect_escapable_u64_swar_unsafe(block);
}
EOF

JSON_MODE=SWAR npx asc ./build/swar-detect-inspect.ts \
  --transform ./transform \
  -O3 \
  --converge \
  --noAssert \
  --uncheckedBehavior always \
  --runtime incremental \
  --textFile ./build/swar-detect-inspect.wat \
  -o ./build/swar-detect-inspect.wasm

Inspect the WAT

sed -n '/(func $build\\/swar-detect-inspect\\/safe/,/^(func/p' ./build/swar-detect-inspect.wat
sed -n '/(func $build\\/swar-detect-inspect\\/unsafe/,/^(func/p' ./build/swar-detect-inspect.wat

Or disassemble the .wasm after the fact:

wasm2wat ./build/swar-detect-inspect.wasm | less
wasm-objdump -d ./build/swar-detect-inspect.wasm | less

What to expect

• The unsafe detector compiles to a smaller function body.
• The safe detector carries extra work for the high-byte mask and final merge.
• That extra code matches the throughput gap in the benchmark: safer semantics, slightly more work.