1 files changed, 72 insertions, 0 deletions
diff --git a/src/ir/module-splitting.h b/src/ir/module-splitting.h
new file mode 100644
index 000000000..765a1f853
--- /dev/null
+++ b/src/ir/module-splitting.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2020 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.
+ */
+
+// module-splitting.h: Provides an interface for decomposing WebAssembly modules
+// into multiple modules that can be loaded independently. This works by moving
+// functions to a new secondary module and rewriting the primary module to call
+// them indirectly. Until the secondary module is instantiated, those indirect
+// calls will go to placeholder functions newly imported into the primary
+// module. The import names of the placeholder functions are the table indexes
+// they are placed at. The secondary module imports all of its dependencies from
+// the primary module.
+//
+// This code currently makes a few assumptions about the modules that will be
+// split and will fail assertions if those assumptions are not true.
+//
+//   1) It assumes that mutable-globals are allowed.
+//
+//   2) It assumes that all table segment offsets are constants.
+//
+//   3) It assumes that each function appears in the table at most once.
+//
+// These requirements will be relaxed as necessary in the future, but for now
+// this code should be considered experimental and used with care.
+
+#ifndef wasm_ir_module_splitting_h
+#define wasm_ir_module_splitting_h
+
+#include "wasm.h"
+
+namespace wasm {
+
+namespace ModuleSplitting {
+
+struct Config {
+  // The set of functions to keep in the primary module. All others are split
+  // out into the new secondary module. Must include the start function if it
+  // exists. May or may not include imported functions, which are always kept in
+  // the primary module regardless.
+  std::set<Name> primaryFuncs;
+  // The namespace from which to import primary functions into the secondary
+  // module.
+  Name importNamespace = "primary";
+  // The namespace from which to import placeholder functions into the primary
+  // module.
+  Name placeholderNamespace = "placeholder";
+  // The prefix to attach to the name of any newly created exports. This can be
+  // used to differentiate between "real" exports of the module and exports that
+  // should only be consumed by the secondary module.
+  std::string newExportPrefix = "";
+};
+
+// Returns the new secondary module and modifies the `primary` module in place.
+std::unique_ptr<Module> splitFunctions(Module& primary, const Config& config);
+
+} // namespace ModuleSplitting
+
+} // namespace wasm
+
+#endif // wasm_ir_module_splitting_h