Add event section (#2151)

This adds support for the event and the event section, as specified in
https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md#changes-to-the-binary-model.

Wasm events are features that suspend the current execution and transfer
the control flow to a corresponding handler. Currently the only
supported event kind is exceptions.

For events, this includes support for
- Binary file reading/writing
- Wast file reading/writing
- Binaryen.js API
- Fuzzer
- Validation
- Metadce
- Passes: metrics, minify-imports-and-exports,
  remove-unused-module-elements

1 files changed, 23 insertions, 1 deletions

diff --git a/src/ir/import-utils.h b/src/ir/import-utils.h
index 950b9bfcb..3f3d27f1b 100644
--- a/src/ir/import-utils.h
+++ b/src/ir/import-utils.h
@@ -29,6 +29,7 @@ struct ImportInfo {
 
   std::vector<Global*> importedGlobals;
   std::vector<Function*> importedFunctions;
+  std::vector<Event*> importedEvents;
 
   ImportInfo(Module& wasm) : wasm(wasm) {
     for (auto& import : wasm.globals) {
@@ -41,6 +42,11 @@ struct ImportInfo {
         importedFunctions.push_back(import.get());
       }
     }
+    for (auto& import : wasm.events) {
+      if (import->imported()) {
+        importedEvents.push_back(import.get());
+      }
+    }
   }
 
   Global* getImportedGlobal(Name module, Name base) {
@@ -61,13 +67,25 @@ struct ImportInfo {
     return nullptr;
   }
 
+  Event* getImportedEvent(Name module, Name base) {
+    for (auto* import : importedEvents) {
+      if (import->module == module && import->base == base) {
+        return import;
+      }
+    }
+    return nullptr;
+  }
+
   Index getNumImportedGlobals() { return importedGlobals.size(); }
 
   Index getNumImportedFunctions() { return importedFunctions.size(); }
 
+  Index getNumImportedEvents() { return importedEvents.size(); }
+
   Index getNumImports() {
     return getNumImportedGlobals() + getNumImportedFunctions() +
-           (wasm.memory.imported() ? 1 : 0) + (wasm.table.imported() ? 1 : 0);
+           getNumImportedEvents() + (wasm.memory.imported() ? 1 : 0) +
+           (wasm.table.imported() ? 1 : 0);
   }
 
   Index getNumDefinedGlobals() {
@@ -77,6 +95,10 @@ struct ImportInfo {
   Index getNumDefinedFunctions() {
     return wasm.functions.size() - getNumImportedFunctions();
   }
+
+  Index getNumDefinedEvents() {
+    return wasm.events.size() - getNumImportedEvents();
+  }
 };
 
 } // namespace wasm