If a SCC has a node without a function, then the SCC

analysis would bail out without removing function
records for other members of the SCC (which may exist
if those functions read or wrote global variables).
Since these are initialized to "readnone", this
resulted in incorrect alias analysis results.

llvm-svn: 55714

1 files changed, 14 insertions, 9 deletions

diff --git a/llvm/lib/Analysis/IPA/GlobalsModRef.cpp b/llvm/lib/Analysis/IPA/GlobalsModRef.cpp
index fe622f26404..9a7580b9c8d 100644
--- a/llvm/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/llvm/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -354,13 +354,18 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
   for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG); I != E;
        ++I) {
     std::vector<CallGraphNode *> &SCC = *I;
-    assert(!SCC.empty() && "SCC with no functions?");
 
-    if (!SCC[0]->getFunction())
-      // Do not process the external node, assume the worst.
-      continue;
+    FunctionRecord *FR = 0;
+    // Find a function record from the SCC (it doesn't matter which one).
+    for (unsigned i = 0, e = SCC.size(); i != e; ++i)
+      if (Function *F = SCC[i]->getFunction()) {
+        FR = &FunctionInfo[F];
+        break;
+      }
 
-    FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()];
+    if (!FR)
+      // Nothing to do.
+      continue;
 
     bool KnowNothing = false;
     unsigned FunctionEffect = 0;
@@ -384,7 +389,7 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
           // mark all globals read somewhere as being read by this function.
           for (std::set<GlobalValue*>::iterator GI = ReadGlobals.begin(),
                E = ReadGlobals.end(); GI != E; ++GI)
-            FR.GlobalInfo[*GI] |= Ref;
+            FR->GlobalInfo[*GI] |= Ref;
         } else {
           // Can't say anything useful.
           KnowNothing = true;
@@ -403,7 +408,7 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
             for (std::map<GlobalValue*, unsigned>::iterator GI =
                    CalleeFR->GlobalInfo.begin(), E = CalleeFR->GlobalInfo.end();
                  GI != E; ++GI)
-              FR.GlobalInfo[GI->first] |= GI->second;
+              FR->GlobalInfo[GI->first] |= GI->second;
           } else {
             // Can't say anything about it.  However, if it is inside our SCC,
             // then nothing needs to be done.
@@ -440,12 +445,12 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
       ++NumReadMemFunctions;
     if (FunctionEffect == 0)
       ++NumNoMemFunctions;
-    FR.FunctionEffect = FunctionEffect;
+    FR->FunctionEffect = FunctionEffect;
 
     // Finally, now that we know the full effect on this SCC, clone the
     // information to each function in the SCC.
     for (unsigned i = 1, e = SCC.size(); i != e; ++i)
-      FunctionInfo[SCC[i]->getFunction()] = FR;
+      FunctionInfo[SCC[i]->getFunction()] = *FR;
   }
 }