Fix PR8300 by remembering to keep the bitcast in all cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116788 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Linker/LinkModules.cpp

@@ -668,6 +668,13 @@ static bool LinkAlias(Module *Dest, const Module *Src,
     GlobalValue* DAliasee = cast<GlobalValue>(VMI->second);
     GlobalValue* DGV = NULL;
 
+    // Fixup aliases to bitcasts.  Note that aliases to GEPs are still broken
+    // by this, but aliases to GEPs are broken to a lot of other things, so
+    // it's less important.
+    Constant *DAliaseeConst = DAliasee;
+    if (SGA->getType() != DAliasee->getType())
+      DAliaseeConst = ConstantExpr::getBitCast(DAliasee, SGA->getType());
+
     // Try to find something 'similar' to SGA in destination module.
     if (!DGV && !SGA->hasLocalLinkage()) {
       DGV = Dest->getNamedAlias(SGA->getName());
@@ -721,7 +728,7 @@ static bool LinkAlias(Module *Dest, const Module *Src,
                        "': aliasee is not global variable");
 
         NewGA = new GlobalAlias(SGA->getType(), SGA->getLinkage(),
-                                SGA->getName(), DAliasee, Dest);
+                                SGA->getName(), DAliaseeConst, Dest);
         CopyGVAttributes(NewGA, SGA);
 
         // Any uses of DGV need to change to NewGA, with cast, if needed.
@@ -750,7 +757,7 @@ static bool LinkAlias(Module *Dest, const Module *Src,
                        "': aliasee is not function");
 
         NewGA = new GlobalAlias(SGA->getType(), SGA->getLinkage(),
-                                SGA->getName(), DAliasee, Dest);
+                                SGA->getName(), DAliaseeConst, Dest);
         CopyGVAttributes(NewGA, SGA);
 
         // Any uses of DF need to change to NewGA, with cast, if needed.
@@ -772,14 +779,8 @@ static bool LinkAlias(Module *Dest, const Module *Src,
     } else {
       // No linking to be performed, simply create an identical version of the
       // alias over in the dest module...
-      Constant *Aliasee = DAliasee;
-      // Fixup aliases to bitcasts.  Note that aliases to GEPs are still broken
-      // by this, but aliases to GEPs are broken to a lot of other things, so
-      // it's less important.
-      if (SGA->getType() != DAliasee->getType())
-        Aliasee = ConstantExpr::getBitCast(DAliasee, SGA->getType());
       NewGA = new GlobalAlias(SGA->getType(), SGA->getLinkage(),
-                              SGA->getName(), Aliasee, Dest);
+                              SGA->getName(), DAliaseeConst, Dest);
       CopyGVAttributes(NewGA, SGA);
 
       // Proceed to 'common' steps

test/Linker/PR8300.ll

@@ -0,0 +1,13 @@
+; RUN: echo {%foo2 = type \{ \[8 x i8\] \} \
+; RUN:       declare void @zed(%foo2*) } > %t.ll
+; RUN: llvm-link %t.ll %s -o %t.bc
+
+%foo = type { [8 x i8] }
+%bar = type { [9 x i8] }
+
+@zed = alias bitcast (void (%bar*)* @xyz to void (%foo*)*)
+
+define void @xyz(%bar* %this) {
+entry:
+  ret void
+}