[llvm] [AMDGPU][SplitModule] Cleanup CallsExternal Handling (PR #106528)

[Matt Arsenault via llvm-commits]

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@@ -492,29 +501,51 @@ void SplitGraph::buildGraph(CallGraph &CG) {
       continue;
 
     // Look at direct callees and create the necessary edges in the graph.
-    bool HasIndirectCall = false;
-    Node &N = getNode(Cache, Fn);
+    SetVector<const Function *> DirectCallees;
+    bool CallsExternal = false;
     for (auto &CGEntry : *CG[&Fn]) {
       auto *CGNode = CGEntry.second;
-      auto *Callee = CGNode->getFunction();
-      if (!Callee) {
-        // TODO: Don't consider inline assembly as indirect calls.
-        if (CGNode == CG.getCallsExternalNode())
-          HasIndirectCall = true;
-        continue;
-      }
-
-      if (!Callee->isDeclaration())
-        createEdge(N, getNode(Cache, *Callee), EdgeKind::DirectCall);
+      if (auto *Callee = CGNode->getFunction()) {
+        if (!Callee->isDeclaration())
+          DirectCallees.insert(Callee);
+      } else if (CGNode == CG.getCallsExternalNode())
+        CallsExternal = true;
     }
 
     // Keep track of this function if it contains an indirect call and/or if it
     // can be indirectly called.
-    if (HasIndirectCall) {
-      LLVM_DEBUG(dbgs() << "indirect call found in " << Fn.getName() << "\n");
-      FnsWithIndirectCalls.push_back(&Fn);
+    if (CallsExternal) {
+      LLVM_DEBUG(dbgs() << "  [!] callgraph is incomplete for ";
+                 Fn.printAsOperand(dbgs());
+                 dbgs() << " - analyzing function\n");
+
+      bool HasIndirectCall = false;
+      for (const auto &Inst : instructions(Fn)) {
+        // look at all calls without a direct callee.
+        if (const auto *CB = dyn_cast<CallBase>(&Inst);
+            CB && !CB->getCalledFunction()) {
+          // inline assembly can be ignored, unless InlineAsmIsIndirectCall is
+          // true.
+          if (CB->isInlineAsm()) {
+            LLVM_DEBUG(dbgs() << "    found inline assembly\n");
+            continue;
+          }
+
+          // everything else is handled conservatively.
+          HasIndirectCall = true;
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arsenm wrote:

Can break at this point? Also can just turn this into a helper function to scan for indirect calls and use early return 

https://github.com/llvm/llvm-project/pull/106528