[NFC] Convert LocalGraph influences accesses to function calls (#6899)

This replaces direct access of the data structure graph.*influences[foo] with a call
graph.get*influences(foo). This will allow a later PR to make those calls optionally
lazy.

1 files changed, 25 insertions, 5 deletions

diff --git a/src/ir/local-graph.h b/src/ir/local-graph.h
index 8ff4ee3be..17cc6ff31 100644
--- a/src/ir/local-graph.h
+++ b/src/ir/local-graph.h
@@ -74,7 +74,8 @@ struct LocalGraph {
   bool equivalent(LocalGet* a, LocalGet* b);
 
   // Optional: compute the influence graphs between sets and gets (useful for
-  // algorithms that propagate changes).
+  // algorithms that propagate changes). Set influences are the gets that can
+  // read from it; get influences are the sets that can (directly) read from it.
   void computeSetInfluences();
   void computeGetInfluences();
 
@@ -83,11 +84,27 @@ struct LocalGraph {
     computeGetInfluences();
   }
 
-  // for each get, the sets whose values are influenced by that get
-  using GetInfluences = std::unordered_set<LocalSet*>;
-  std::unordered_map<LocalGet*, GetInfluences> getInfluences;
   using SetInfluences = std::unordered_set<LocalGet*>;
-  std::unordered_map<LocalSet*, SetInfluences> setInfluences;
+  using GetInfluences = std::unordered_set<LocalSet*>;
+
+  const SetInfluences& getSetInfluences(LocalSet* set) const {
+    auto iter = setInfluences.find(set);
+    if (iter == setInfluences.end()) {
+      // Use a canonical constant empty set to avoid allocation.
+      static const SetInfluences empty;
+      return empty;
+    }
+    return iter->second;
+  }
+  const GetInfluences& getGetInfluences(LocalGet* get) const {
+    auto iter = getInfluences.find(get);
+    if (iter == getInfluences.end()) {
+      // Use a canonical constant empty set to avoid allocation.
+      static const GetInfluences empty;
+      return empty;
+    }
+    return iter->second;
+  }
 
   // Optional: Compute the local indexes that are SSA, in the sense of
   //  * a single set for all the gets for that local index
@@ -132,6 +149,9 @@ private:
   // with that. It could alternatively be a shared_ptr, but that runs into what
   // seems to be a false positive of clang's (but not gcc's) UBSan.
   std::unique_ptr<LocalGraphFlower> flower;
+
+  std::unordered_map<LocalSet*, SetInfluences> setInfluences;
+  std::unordered_map<LocalGet*, GetInfluences> getInfluences;
 };
 
 } // namespace wasm