Improve NameTypes to keep reasonable names (#3977)

We only set a name now if there was no name, or the existing name
was really really long.

1 files changed, 9 insertions, 5 deletions

diff --git a/src/passes/NameTypes.cpp b/src/passes/NameTypes.cpp
index 2939f9ad5..a2c5016bc 100644
--- a/src/passes/NameTypes.cpp
+++ b/src/passes/NameTypes.cpp
@@ -21,14 +21,14 @@
 //
 // Ensures each type has a name. This can be useful for debugging.
 //
-// TODO: keep existing useful (short-enough) names, and just replace ones that
-//       are bothersome
-//
 
 using namespace std;
 
 namespace wasm {
 
+// An arbitrary limit, above which we rename types.
+static const size_t NameLenLimit = 20;
+
 struct NameTypes : public Pass {
   void run(PassRunner* runner, Module* module) override {
     // Find all the types.
@@ -36,10 +36,14 @@ struct NameTypes : public Pass {
     std::unordered_map<HeapType, Index> typeIndices;
     ModuleUtils::collectHeapTypes(*module, types, typeIndices);
 
-    // Ensure simple names.
+    // Ensure simple names. If a name already exists, and is short enough, keep
+    // it.
     size_t i = 0;
     for (auto& type : types) {
-      module->typeNames[type].name = "type$" + std::to_string(i++);
+      if (module->typeNames.count(type) == 0 ||
+          module->typeNames[type].name.size() >= NameLenLimit) {
+        module->typeNames[type].name = "type$" + std::to_string(i++);
+      }
     }
   }
 };