[dart2wasm] Cache closure implementations in Translator

Change-Id: I9afd348d81cfababd445bdb9c46cf3e6628f947a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/397320
Reviewed-by: Martin Kustermann <[email protected]>
Commit-Queue: Ömer Ağacan <[email protected]>

Author: osa1

pkg/dart2wasm/lib/translator.dart

@@ -159,6 +159,8 @@ class Translator with KernelNodes {
   final Map<w.BaseFunction, w.Global> functionRefCache = {};
   final Map<Procedure, ClosureImplementation> tearOffFunctionCache = {};
 
+  final Map<FunctionNode, ClosureImplementation> closureImplementations = {};
+
   // Some convenience accessors for commonly used values.
   late final ClassInfo topInfo = classes[0];
   late final ClassInfo objectInfo = classInfo[coreTypes.objectClass]!;
@@ -723,6 +725,23 @@ class Translator with KernelNodes {
 
   ClosureImplementation getClosure(FunctionNode functionNode,
       w.BaseFunction target, ParameterInfo paramInfo, String name) {
+    // We compile a block multiple times in try-catch, to catch Dart exceptions
+    // and then again to catch JS exceptions. We may also ask for
+    // `ClosureImplementation` for a local function multiple times as we see
+    // direct calls to the closure (in TFA direct-call metadata). Avoid
+    // recompiling the closures in these cases by caching implementations.
+    //
+    // Note that every `FunctionNode` passed to this method will have one
+    // `ParameterInfo` for them. For local functions, the `ParameterInfo` will
+    // be the one generated by `ParameterInfo.fromLocalFunction`, for others it
+    // will be the value returned by `paramInfoForDirectCall`. So the key for
+    // this cache can be just `FunctionNode`, instead of `(FunctionNode,
+    // ParameterInfo)`.
+    final existingImplementation = closureImplementations[functionNode];
+    if (existingImplementation != null) {
+      return existingImplementation;
+    }
+
     final targetModule = target.enclosingModule;
 
     // Look up the closure representation for the signature.
@@ -850,8 +869,10 @@ class Translator with KernelNodes {
     ib.struct_new(representation.vtableStruct);
     ib.end();
 
-    return ClosureImplementation(
+    final implementation = ClosureImplementation(
         representation, functions, dynamicCallEntry, vtable, targetModule);
+    closureImplementations[functionNode] = implementation;
+    return implementation;
   }
 
   w.ValueType outputOrVoid(List<w.ValueType> outputs) {