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

[Kazu Hirata via llvm-commits]

================
@@ -1103,6 +1154,57 @@ void CallsiteContextGraph<DerivedCCG, FuncTy, CallTy>::connectNewNode(
   }
 }
 
+template <typename DerivedCCG, typename FuncTy, typename CallTy>
+static void checkEdge(
+    const std::shared_ptr<ContextEdge<DerivedCCG, FuncTy, CallTy>> &Edge) {
+  // Confirm that alloc type is not None and that we have at least one context
+  // id.
+  assert(Edge->AllocTypes != (uint8_t)AllocationType::None);
+  assert(!Edge->ContextIds.empty());
+}
+
+template <typename DerivedCCG, typename FuncTy, typename CallTy>
+static void checkNode(const ContextNode<DerivedCCG, FuncTy, CallTy> *Node,
+                      bool CheckEdges = true) {
+  if (Node->isRemoved())
+    return;
+#ifndef NDEBUG
+  // Compute node's context ids once for use in asserts.
+  auto NodeContextIds = Node->getContextIds();
+#endif
+  // Node's context ids should be the union of both its callee and caller edge
+  // context ids.
+  if (Node->CallerEdges.size()) {
+    auto EI = Node->CallerEdges.begin();
+    auto &FirstEdge = *EI;
+    EI++;
+    DenseSet<uint32_t> CallerEdgeContextIds(FirstEdge->ContextIds);
+    for (; EI != Node->CallerEdges.end(); EI++) {
+      const auto &Edge = *EI;
----------------
kazutakahirata wrote:

May I suggest `drop_begin` like so?

```suggestion
    DenseSet<uint32_t> CallerEdgeContextIds(Node->CallerEdges.front()->ContextIds);
    for (const auto &Edge : llvm::drop_begin(Node->CallerEdges)) {
```


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