[NewPM] Bail out of devirtualization wrapper if the current SCC is invalidated

[aeubanks]

Summary

The specific case that triggered this was when inlining a recursive
internal function into itself caused the recursion to go away, allowing
the inliner to mark the function as dead. The inliner marks the SCC as
invalidated but does not provide a new SCC to continue with.

This matches the implementations of ModuleToPostOrderCGSCCPassAdaptor
and CGSCCPassManager.

Fixes PR50363.

[asbirlea]

Thank you for tracking this down!

llvm/lib/Analysis/CGSCCPassManager.cpp

for (int Iteration = 0;; ++Iteration) {
 
     // If the SCC structure has changed, bail immediately and let the outer
     // CGSCC layer handle any iteration to reflect the refined structure.
     if (UR.UpdatedC && UR.UpdatedC != C) {
       PA.intersect(std::move(PassPA));
       break;
     }
 
-    // Check that we didn't miss any update scenario.
-    assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
+    // If the CGSCC pass wasn't able to provide a valid updated SCC, the
+    // current SCC may simply need to be skipped if invalid.
+    if (UR.InvalidatedSCCs.count(C)) {
+      LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
+      break;
+    }
+
     assert(C->begin() != C->end() && "Cannot have an empty SCC!");
 
     // Check whether any of the handles were devirtualized.
     bool Devirt = llvm::any_of(UR.IndirectVHs, [](auto &P) -> bool {
       if (P.second) {
         if (CallBase *CB = dyn_cast<CallBase>(P.second)) {
           if (CB->getCalledFunction()) {
             LLVM_DEBUG(dbgs() << "Found devirtualized call: " << *CB << "\n");

llvm/test/Other/devirt-invalidated.ll

+; RUN: opt -passes='devirt<0>(inline)' < %s -S | FileCheck %s
+
+; CHECK-NOT: internal
+; CHECK: define void @e()
+; CHECK-NOT: internal
+
+define void @e() {
+entry:
+  call void @b()
+  ret void
+}
+
+define internal void @b() {
+entry:
+  call void @d()
+  call void @c()
+  ret void
+}
+
+define internal void @d() {
+entry:
+  unreachable
+}
+
+define internal void @c() {
+entry:
+  call void @b()
+  call void @e()
+  ret void
+}