[Wasm GC][GUFA] Avoid Many in roots (#5142)

Instead of Many, use a proper Cone Type for the data, as appropriate.

2 files changed, 36 insertions, 8 deletions

diff --git a/src/ir/possible-contents.cpp b/src/ir/possible-contents.cpp
index cd8bd1516..2efd61391 100644
--- a/src/ir/possible-contents.cpp
+++ b/src/ir/possible-contents.cpp
@@ -1205,6 +1205,9 @@ struct InfoCollector
                PossibleContents contents = PossibleContents::many()) {
     // TODO Use a cone type here when relevant
     if (isRelevant(curr)) {
+      if (contents.isMany()) {
+        contents = PossibleContents::fromType(curr->type);
+      }
       addRoot(ExpressionLocation{curr, 0}, contents);
     }
   }
@@ -1399,8 +1402,10 @@ Flower::Flower(Module& wasm) : wasm(wasm) {
 
       if (func->imported()) {
         // Imports return unknown values.
-        for (Index i = 0; i < func->getResults().size(); i++) {
-          finder.addRoot(ResultLocation{func, i}, PossibleContents::many());
+        auto results = func->getResults();
+        for (Index i = 0; i < results.size(); i++) {
+          finder.addRoot(ResultLocation{func, i},
+                         PossibleContents::fromType(results[i]));
         }
         return;
       }
@@ -1423,7 +1428,8 @@ Flower::Flower(Module& wasm) : wasm(wasm) {
   for (auto& global : wasm.globals) {
     if (global->imported()) {
       // Imports are unknown values.
-      finder.addRoot(GlobalLocation{global->name}, PossibleContents::many());
+      finder.addRoot(GlobalLocation{global->name},
+                     PossibleContents::fromType(global->type));
       continue;
     }
     auto* init = global->init;
@@ -1477,8 +1483,9 @@ Flower::Flower(Module& wasm) : wasm(wasm) {
   // that we can't see, so anything might arrive there.
   auto calledFromOutside = [&](Name funcName) {
     auto* func = wasm.getFunction(funcName);
+    auto params = func->getParams();
     for (Index i = 0; i < func->getParams().size(); i++) {
-      roots[ParamLocation{func, i}] = PossibleContents::many();
+      roots[ParamLocation{func, i}] = PossibleContents::fromType(params[i]);
     }
   };
 
@@ -1509,8 +1516,9 @@ Flower::Flower(Module& wasm) : wasm(wasm) {
       // Exported mutable globals are roots, since the outside may write any
       // value to them.
       auto name = ex->value;
-      if (wasm.getGlobal(name)->mutable_) {
-        roots[GlobalLocation{name}] = PossibleContents::many();
+      auto* global = wasm.getGlobal(name);
+      if (global->mutable_) {
+        roots[GlobalLocation{name}] = PossibleContents::fromType(global->type);
       }
     }
   }
@@ -1974,9 +1982,9 @@ void Flower::dump(Location location) {
     std::cout << "  tagloc " << loc->tag << '\n';
   } else if (auto* loc = std::get_if<ParamLocation>(&location)) {
     std::cout << "  paramloc " << loc->func->name << " : " << loc->index
-              << " tupleIndex " << loc->tupleIndex << '\n';
+              << '\n';
   } else if (auto* loc = std::get_if<ResultLocation>(&location)) {
-    std::cout << "  resultloc " << loc->func->name << " : " << loc->index
+    std::cout << "  resultloc $" << loc->func->name << " : " << loc->index
               << '\n';
   } else if (auto* loc = std::get_if<GlobalLocation>(&location)) {
     std::cout << "  globalloc " << loc->name << '\n';
diff --git a/src/ir/possible-contents.h b/src/ir/possible-contents.h
index ee817deae..14ed36b4d 100644
--- a/src/ir/possible-contents.h
+++ b/src/ir/possible-contents.h
@@ -131,6 +131,26 @@ public:
   }
   static PossibleContents many() { return PossibleContents{Many()}; }
 
+  // Helper for creating a PossibleContents based on a wasm type, that is, where
+  // all we know is the wasm type.
+  static PossibleContents fromType(Type type) {
+    assert(type != Type::none);
+
+    if (type.isRef()) {
+      // For a reference, subtyping matters.
+      return fullConeType(type);
+    }
+
+    if (type == Type::unreachable) {
+      // Nothing is possible here.
+      return none();
+    }
+
+    // Otherwise, this is a concrete MVP type.
+    assert(type.isConcrete());
+    return exactType(type);
+  }
+
   PossibleContents& operator=(const PossibleContents& other) = default;
 
   bool operator==(const PossibleContents& other) const {