[llvm] [XRay] Use DenseMap::{operator[], try_emplace} (NFC) (PR #107178)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-xray

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>

I'm planning to deprecate DenseMap::FindAndConstruct in favor of
operator[].  I'm using try_emplace because "Vertices[I.first];" on its
own might look like a nop statement.


---
Full diff: https://github.com/llvm/llvm-project/pull/107178.diff


1 Files Affected:

- (modified) llvm/include/llvm/XRay/Graph.h (+7-9) 


``````````diff
diff --git a/llvm/include/llvm/XRay/Graph.h b/llvm/include/llvm/XRay/Graph.h
index 953ac1aa696371..6c8b178e58ff8c 100644
--- a/llvm/include/llvm/XRay/Graph.h
+++ b/llvm/include/llvm/XRay/Graph.h
@@ -378,20 +378,18 @@ class Graph {
 
   /// Looks up the vertex with identifier I, if it does not exist it default
   /// constructs it.
-  VertexAttribute &operator[](const VertexIdentifier &I) {
-    return Vertices.FindAndConstruct(I).second;
-  }
+  VertexAttribute &operator[](const VertexIdentifier &I) { return Vertices[I]; }
 
   /// Looks up the edge with identifier I, if it does not exist it default
   /// constructs it, if it's endpoints do not exist it also default constructs
   /// them.
   EdgeAttribute &operator[](const EdgeIdentifier &I) {
-    auto &P = Edges.FindAndConstruct(I);
-    Vertices.FindAndConstruct(I.first);
-    Vertices.FindAndConstruct(I.second);
+    auto &Attr = Edges[I];
+    Vertices.try_emplace(I.first);
+    Vertices.try_emplace(I.second);
     InNeighbors[I.second].insert(I.first);
     OutNeighbors[I.first].insert(I.second);
-    return P.second;
+    return Attr;
   }
 
   /// Looks up a vertex with Identifier I, or an error if it does not exist.
@@ -479,8 +477,8 @@ class Graph {
     auto EI = Val.first;
     const auto &p = Edges.insert(std::move(Val));
     if (p.second) {
-      Vertices.FindAndConstruct(EI.first);
-      Vertices.FindAndConstruct(EI.second);
+      Vertices.try_emplace(EI.first);
+      Vertices.try_emplace(EI.second);
       InNeighbors[EI.second].insert(EI.first);
       OutNeighbors[EI.first].insert(EI.second);
     };

``````````

</details>


https://github.com/llvm/llvm-project/pull/107178