[Parser][NFC] Split parser into multiple compilation units (#6653)

Because the parser has five stages, it requires instantiating all of the
templates in parsers.h with up to five different contexts. Instantiating all
those templates in a single compilation unit takes a long time. On my machine, a
release build of wat-parser.cpp.o took 32 seconds. To reduce the time of
incremental rebuilds on machines with many cores, split the code across several
compilation units so that the templates need to be instantiated for just a
single context in each unit. On my machine the longest compilation time after
this splitting is 17 seconds. The time for a full release build also drops from
42 seconds to 33 seconds. On machines with fewer cores, the benefit may be
smaller or even negative, though.

1 files changed, 23 insertions, 0 deletions

diff --git a/src/parser/parse-1-decls.cpp b/src/parser/parse-1-decls.cpp
new file mode 100644
index 000000000..1c753cc61
--- /dev/null
+++ b/src/parser/parse-1-decls.cpp
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2024 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "wat-parser-internal.h"
+
+namespace wasm::WATParser {
+
+Result<> parseDecls(ParseDeclsCtx& decls) { return module(decls); }
+
+} // namespace wasm::WATParser