codegen: inline proto2 extension writers/readers (qwt) + table.new(N,0) for packed lists (2sn)
qwt closes the proto2_basic.BenchPayload `min` bench's worst data point:
encode 1.89M → 3.30M msgs/s (+75%), decode 1.02M → 1.26M msgs/s (+23%).
Mechanism: collectExtsByExtendee groups all `extend Foo { ... }`
declarations by extendee FullName across input files; emitInlineEncode
emits one dedicated writer per extension instead of dispatching through
pb.codec.encode_field, and emitInlineDecode adds an elseif arm per
extension id straight into result._extensions[full_name]. Dynamic
extensions_list walk preserved for forward compat, gated on
#_elist > N so it pays one int compare when no runtime extension was
registered.
2sn pre-sizes packed-scalar repeated lists via table.new(N, 0) where
the count is recoverable from the LEN payload — exact (lim >> 2 or
lim >> 3) for fixed-width, upper bound (lim) for varint-packed. The
allocation is deferred into the `if wt == 2 then` branch so the
per-element fallback and non-packable types keep the bare-`{}`
alloc. Avoids u39's regression mode because the call cost is paid
once per repeated-field-first-occurrence, not per message decode.
Bench summary for hello.Person full mode: encode +3-5% across sizes,
decode +1-3% across sizes. Tests: 752/752 pure-Lua, 1043/1043 with
PB_ENABLE_C=1, JIT 37/37. PERF_LOG entry covers the rationale and
caveats.
codegen: inline 1-byte LEN fast path for string/bytes decode
Singular and repeated string/bytes fields in generated full-mode _decode
now read the length byte and dispatch in-line instead of calling
wire.decode_string / wire.decode_bytes. For length < 128 (the common
short-string RPC case), the path stays inside the parent JIT trace:
no child-trace stitch, no per-element function frame, utf8_len lookup
hoisted to a generated-file upvalue.
The original a6n design — one ffi.cast(U8CP, buf) at the top of each
_decode — was abandoned: the cdata wrapper is 24 bytes per call and
LuaJIT can't sink the allocation because the pointer local lives
across wire.decode_* call frames. Net regression at small sizes
(+11-16%) overwhelmed the single-byte-read savings.
Bench (hello.Person full-mode decode):
size ns/op before ns/op after delta
10B 419 390 -6.9%
100B 515 478 -7.2%
1KB 9004 8042 -10.7%
10KB 64644 56745 -12.2%
100KB 625638 537750 -14.0%
Zero allocation impact across all sizes. Tests: 1043 pass, 37 JIT
trace gates pass. (a6n)
c_runtime: wire encode/decode dispatch + conformance-c harness
pb.encode / pb.decode lazy-compile desc.c_plan on first call and route
to pb.c_runtime.encode/decode when PB_ENABLE_C=1 loaded the module.
Eager compile at finalize_message time fails on codegen's
forward-declared descriptors — sub-messages don't have .fields yet —
so compilation is deferred until first encode/decode, by which time
the whole module table is populated and sub-plan chase resolves.
Full-mode codegen wrappers (M.<Type>_{encode,decode}) gain the same
lazy-compile prologue, bypassing the inline body when the C runtime
is loaded. Runtime-mode wrappers already call pb.encode and pick up
dispatch centrally.
Harness side: the conformance Docker image now installs tarantool-dev
+ build-essential so the C runtime can be built in-container; a new
`just conformance-c` recipe builds runtime/pb/c_runtime.so inside the
container, runs the suite with PB_ENABLE_C=1, then cleans the .so to
keep the bind mount free of foreign-platform binaries. The runner
script also pre-populates package.loaded.pb (avoids
.rocks/lib/tarantool/pb.so from starwing lua-protobuf masking ours)
and orders package.cpath by jit.os so mixed .dylib/.so trees from
host/container interleavings don't cross-load.
Verified:
- just test → 748 pass, 291 C-conditional skipped
- PB_ENABLE_C=1 just test → 1026/1039 pass; 13 fails are strict-decode
gaps in the C decoder (bd-rc8)
- just conformance-c → 2729/2806 binary suite pass; 77 unexpected
failures match the same gap categories
(illegal wire-type 6/7, field-num 0/over,
overlong tag varint, UTF-8 rejection,
message merge for oneof/repeated)
Strict-decode parity tracked in bd-rc8; this commit closes the wiring
half of bd-43t (conformance gate for C paths).
c_runtime: encode/decode singular sub-messages (ra6 3d)
Refactor encode_lua/decode_lua into encode_body/decode_body so the
field-walk loop is callable recursively, then dispatch the MESSAGE
kind into a per-side sub-handler. Repeated and map fields still skip
at the field-walk level — 3e (jc9) and 3h (asz) land them next.
encode_submessage_field force-establishes the parent enc_buf's
heap_idx via a no-op ebuf_grow before recursing. Without that the
final ebuf_reserve on the parent could land its new userdata above
sub-encode's leaked stack slots, making the closing lua_settop drop
the parent's heap.
decode_submessage_field bounds the inner read by temporarily
shrinking c->len to the sub-message end offset; the wire-prim
helpers already bounds-check against c->len, so a malformed inner
payload can't over-read into the outer message's bytes.
New fixture test/proto/c_nested.proto carries a 5-level singular
chain (L1->L2->L3->L4->L5) for the depth test. The two existing
"skip message" tests are renamed to "skip repeated and map" — sub-
messages now encode and decode end-to-end.
bd-hwe