BasicAA was making the assumption that a local allocation which hadn't escaped

couldn't ever be the return of call instruction. However, it's quite possible
that said local allocation is itself the return of a function call. That's
what malloc and calloc are for, actually.

llvm-svn: 64442

llvm/lib/Analysis/BasicAliasAnalysis.cpp

@@ -319,7 +319,7 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
     // If the pointer is to a locally allocated object that does not escape,
     // then the call can not mod/ref the pointer unless the call takes the
     // argument without capturing it.
-    if (isNonEscapingLocalObject(Object)) {
+    if (isNonEscapingLocalObject(Object) && CS.getInstruction() != Object) {
       bool passedAsArg = false;
       // TODO: Eventually only check 'nocapture' arguments.
       for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
@@ -414,10 +414,10 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
   // non-escaping local object, then we know the object couldn't escape to a
   // point where the call could return it.
   if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
-      isNonEscapingLocalObject(O2))
+      isNonEscapingLocalObject(O2) && O1 != O2)
     return NoAlias;
   if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
-      isNonEscapingLocalObject(O1))
+      isNonEscapingLocalObject(O1) && O1 != O2)
     return NoAlias;
   
   // If we have two gep instructions with must-alias'ing base pointers, figure