[llvm] [MemProf] Remove context id set from nodes and recompute on demand (PR #94415)

[Kazu Hirata via llvm-commits]

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@@ -262,8 +262,70 @@ class CallsiteContextGraph {
     // TODO: Should this be a map (from Caller node) for more efficient lookup?
     std::vector<std::shared_ptr<ContextEdge>> CallerEdges;
 
-    // The set of IDs for contexts including this node.
-    DenseSet<uint32_t> ContextIds;
+    // Get the list of edges from which we can compute allocation information
+    // such as the context ids and allocation type of this node.
+    const std::vector<std::shared_ptr<ContextEdge>> *
+    getEdgesWithAllocInfo() const {
+      // If node has any callees, compute from those, otherwise compute from
+      // callers (i.e. if this is the leaf allocation node).
+      if (!CalleeEdges.empty())
+        return &CalleeEdges;
+      else if (!CallerEdges.empty()) {
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kazutakahirata wrote:

Remove the `else` after `return`.

```suggestion
      if (!CallerEdges.empty()) {
```

https://github.com/llvm/llvm-project/pull/94415