Improve indirect call effects in GlobalEffects

src/passes/GlobalEffects.cpp

@@ -22,6 +22,7 @@
 #include <ranges>
 
 #include "ir/effects.h"
+#include "ir/element-utils.h"
 #include "ir/module-utils.h"
 #include "pass.h"
 #include "support/graph_traversal.h"
@@ -47,6 +48,56 @@ struct FuncInfo {
   std::unordered_set<HeapType> indirectCalledTypes;
 };
 
+/*
+ Only funcs that are 'addressed' may be the target of an indirect call. A
+ function is addressed if:
+ - It appears in a ref.func expression
+ - It appears in an `elem` segment (note that we already ignore `elem declare`
+   statements in our IR, but we check separately for funcs that appear in
+   `ref.func`).
+ - It's exported, because it may flow back to us as a reference.
+ - It's imported, which implies it is `elem declare`d.
+
+ If a function doesn't meet any of these criteria, it can't be the target of
+ an indirect call and we don't need to include its effects in indirect calls.
+*/
+std::unordered_set<Function*> getAddressedFuncs(Module& module) {
+  struct AddressedFuncsWalker : PostWalker<AddressedFuncsWalker> {
+    std::unordered_set<Function*>& addressedFuncs;
+
+    AddressedFuncsWalker(std::unordered_set<Function*>& addressedFuncs)
+      : addressedFuncs(addressedFuncs) {}
+
+    void visitRefFunc(RefFunc* refFunc) {
+      addressedFuncs.insert(getModule()->getFunction(refFunc->func));
+    }
+  };
+
+  std::unordered_set<Function*> addressedFuncs;
+  AddressedFuncsWalker walker(addressedFuncs);
+  walker.walkModule(&module);
+
+  ModuleUtils::iterImportedFunctions(
+    module, [&addressedFuncs, &module](Function* import) {
+      addressedFuncs.insert(module.getFunction(import->name));
+    });
+
+  for (const auto& export_ : module.exports) {
+    if (export_->kind != ExternalKind::Function) {
+      continue;
+    }
+
+    addressedFuncs.insert(module.getFunction(*export_->getInternalName()));
+  }
+
+  ElementUtils::iterAllElementFunctionNames(
+    &module, [&addressedFuncs, &module](Name func) {
+      addressedFuncs.insert(module.getFunction(func));
+    });
+
+  return addressedFuncs;
+}
+
 std::map<Function*, FuncInfo> analyzeFuncs(Module& module,
                                            const PassOptions& passOptions) {
   ModuleUtils::ParallelFunctionAnalysis<FuncInfo> analysis(
@@ -147,6 +198,7 @@ using CallGraph =
 
 CallGraph buildCallGraph(const Module& module,
                          const std::map<Function*, FuncInfo>& funcInfos,
+                         const std::unordered_set<Function*>& addressedFuncs,
                          bool closedWorld) {
   CallGraph callGraph;
   if (!closedWorld) {
@@ -182,7 +234,9 @@ CallGraph buildCallGraph(const Module& module,
     }
 
     // Type -> Function
-    callGraph[caller->type.getHeapType()].insert(caller);
+    if (addressedFuncs.contains(caller)) {
+      callGraph[caller->type.getHeapType()].insert(caller);
+    }
   }
 
   // Type -> Type
@@ -346,8 +400,10 @@ struct GenerateGlobalEffects : public Pass {
     std::map<Function*, FuncInfo> funcInfos =
       analyzeFuncs(*module, getPassOptions());
 
-    auto callGraph =
-      buildCallGraph(*module, funcInfos, getPassOptions().closedWorld);
+    auto addressedFuncs = getAddressedFuncs(*module);
+
+    auto callGraph = buildCallGraph(
+      *module, funcInfos, addressedFuncs, getPassOptions().closedWorld);
 
     propagateEffects(*module, getPassOptions(), funcInfos, callGraph);
 

test/lit/passes/global-effects-closed-world.wast

@@ -348,15 +348,12 @@
   )
 
   ;; CHECK:      (func $f (type $1) (param $ref (ref $only-has-effects-in-not-addressable-function))
-  ;; CHECK-NEXT:  (call $calls-type-with-effects-but-not-addressable
-  ;; CHECK-NEXT:   (local.get $ref)
-  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (nop)
   ;; CHECK-NEXT: )
   (func $f (param $ref (ref $only-has-effects-in-not-addressable-function))
     ;; The type $has-effects-but-not-exported doesn't have an address because
     ;; it's not exported and it's never the target of a ref.func.
-    ;; We should be able to determine that $ref can only point to $nop.
-    ;; TODO: Only aggregate effects from functions that are addressed.
+    ;; So the call_ref has no potential targets and thus no effects.
     (call $calls-type-with-effects-but-not-addressable (local.get $ref))
   )
 )