2 files changed, 26 insertions, 6 deletions

diff --git a/src/ir/LocalGraph.cpp b/src/ir/LocalGraph.cpp
index 11965040c..af1370731 100644
--- a/src/ir/LocalGraph.cpp
+++ b/src/ir/LocalGraph.cpp
@@ -552,7 +552,14 @@ bool LocalGraph::isSSA(Index x) { return SSAIndexes.count(x); }
 // LazyLocalGraph
 
 LazyLocalGraph::LazyLocalGraph(Function* func, Module* module)
-  : LocalGraphBase(func, module) {
+  : LocalGraphBase(func, module) {}
+
+void LazyLocalGraph::makeFlower() const {
+  // Lazy graphs do not provide |locations| publicly. TODO: perhaps refactor to
+  // avoid filling in this dummy data structure, but we may want to add a lazy
+  // version of it too, so see which makes sense first.
+  LocalGraph::Locations locations;
+
   flower =
     std::make_unique<LocalGraphFlower>(getSetsMap, locations, func, module);
 
@@ -578,10 +585,16 @@ LazyLocalGraph::~LazyLocalGraph() {
 }
 
 void LazyLocalGraph::computeGetSets(LocalGet* get) const {
+  if (!flower) {
+    makeFlower();
+  }
   flower->computeGetSets(get);
 }
 
 void LazyLocalGraph::computeSetInfluences(LocalSet* set) const {
+  if (!flower) {
+    makeFlower();
+  }
   flower->computeSetInfluences(set, setInfluences);
 }
 
diff --git a/src/ir/local-graph.h b/src/ir/local-graph.h
index 7fe9adedc..46bc135e0 100644
--- a/src/ir/local-graph.h
+++ b/src/ir/local-graph.h
@@ -58,11 +58,8 @@ public:
   // get. Typically only one or two apply there, so this is a small set.
   using Sets = SmallSet<LocalSet*, 2>;
 
-  // Where each get and set is. We compute this while doing the main computation
-  // and make it accessible for users, for easy replacing of things without
-  // extra work.
+  // Where each get and set is.
   using Locations = std::map<Expression*, Expression**>;
-  Locations locations;
 
   // A map of each get to the sets relevant to it (i.e., that it can read from).
   using GetSetsMap = std::unordered_map<LocalGet*, Sets>;
@@ -104,6 +101,11 @@ struct LocalGraph : public LocalGraphBase {
     return iter->second;
   }
 
+  // We compute the locations of gets and sets while doing the main computation
+  // and make it accessible for users, for easy replacing of things without
+  // extra work.
+  Locations locations;
+
   // Checks if two gets are equivalent, that is, definitely have the same
   // value.
   bool equivalent(LocalGet* a, LocalGet* b);
@@ -213,7 +215,12 @@ private:
   void computeSetInfluences(LocalSet* set) const;
 
   // This remains alive as long as we are, so that we can compute things lazily.
-  std::unique_ptr<LocalGraphFlower> flower;
+  // It is mutable as when we construct this is an internal detail, that does
+  // not cause observable differences in API calls.
+  mutable std::unique_ptr<LocalGraphFlower> flower;
+
+  // We create |flower| lazily.
+  void makeFlower() const;
 };
 
 } // namespace wasm