From 34f2a0ca17f00f9ce2081ee278685a007856fd90 Mon Sep 17 00:00:00 2001
From: Duncan Sands <baldrick@free.fr>
Date: Wed, 3 Sep 2008 19:37:16 +0000
Subject: [PATCH] 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55714 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/IPA/GlobalsModRef.cpp | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/lib/Analysis/IPA/GlobalsModRef.cpp b/lib/Analysis/IPA/GlobalsModRef.cpp
index fe622f26404..9a7580b9c8d 100644
--- a/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/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;
   }
 }
 
-- 
2.34.1