Fix PR4834, a tricky case where the inliner would resolve an

indirect function pointer, inline it, then go to delete the body.
The problem is that the callgraph had other references to the function,
though the inliner had no way to know it, so we got a dangling pointer
and an invalid iterator out of the deal.

The fix to this is pretty simple: stop the inliner from deleting the
function by knowing that there are references to it.  Do this by making
CallGraphNodes contain a refcount.  This requires moving deletion of 
available_externally functions to the module-level cleanup sweep where
it belongs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80533 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 6 deletions

diff --git a/lib/Transforms/IPO/Inliner.cpp b/lib/Transforms/IPO/Inliner.cpp
index d5967fb11c..9b8e0a1fc4 100644
--- a/lib/Transforms/IPO/Inliner.cpp
+++ b/lib/Transforms/IPO/Inliner.cpp
@@ -293,10 +293,12 @@ bool Inliner::runOnSCC(std::vector<CallGraphNode*> &SCC) {
       
       // If we inlined the last possible call site to the function, delete the
       // function body now.
-      if (Callee->use_empty() && 
-          (Callee->hasLocalLinkage() ||
-           Callee->hasAvailableExternallyLinkage()) &&
-          !SCCFunctions.count(Callee)) {
+      if (Callee->use_empty() && Callee->hasLocalLinkage() &&
+          !SCCFunctions.count(Callee) &&
+          // The function may be apparently dead, but if there are indirect
+          // callgraph references to the node, we cannot delete it yet, this
+          // could invalidate the CGSCC iterator.
+          CG[Callee]->getNumReferences() == 0) {
         DEBUG(errs() << "    -> Deleting dead function: "
               << Callee->getName() << "\n");
         CallGraphNode *CalleeNode = CG[Callee];
@@ -353,7 +355,7 @@ bool Inliner::removeDeadFunctions(CallGraph &CG,
   // from the program.  Insert the dead ones in the FunctionsToRemove set.
   for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
     CallGraphNode *CGN = I->second;
-    if (CGN == 0 || CGN->getFunction() == 0)
+    if (CGN->getFunction() == 0)
       continue;
     
     Function *F = CGN->getFunction();
@@ -364,7 +366,8 @@ bool Inliner::removeDeadFunctions(CallGraph &CG,
 
     if (DNR && DNR->count(F))
       continue;
-    if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage())
+    if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage() &&
+        !F->hasAvailableExternallyLinkage())
       continue;
     if (!F->use_empty())
       continue;