ThinLTOBitcodeWriter: Do not follow operand edges of type GlobalValue when looking for virtual functions.

Such edges may otherwise result in infinite recursion if a pointer to a vtable
is reachable from the vtable itself. This can happen in practice if a TU
defines the ABI types used to implement RTTI, and is itself compiled with RTTI.

Fixes PR32121.

llvm-svn: 296839

2 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index d6fccb03fec..ac62496e0fe 100644
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -241,6 +241,8 @@ void filterModule(
 void forEachVirtualFunction(Constant *C, function_ref<void(Function *)> Fn) {
   if (auto *F = dyn_cast<Function>(C))
     return Fn(F);
+  if (isa<GlobalValue>(C))
+    return;
   for (Value *Op : C->operands())
     forEachVirtualFunction(cast<Constant>(Op), Fn);
 }
diff --git a/llvm/test/Transforms/ThinLTOBitcodeWriter/circular-reference.ll b/llvm/test/Transforms/ThinLTOBitcodeWriter/circular-reference.ll
new file mode 100644
index 00000000000..eeda7932449
--- /dev/null
+++ b/llvm/test/Transforms/ThinLTOBitcodeWriter/circular-reference.ll
@@ -0,0 +1,9 @@
+; RUN: opt -thinlto-bc -o %t %s
+; RUN: llvm-modextract -b -n 0 -o - %t | llvm-dis | FileCheck --check-prefix=M0 %s
+; RUN: llvm-modextract -b -n 1 -o - %t | llvm-dis | FileCheck --check-prefix=M1 %s
+
+; M0: @g = external constant
+; M1: @g = constant
+@g = constant i8* bitcast (i8** @g to i8*), !type !0
+
+!0 = !{i32 0, !"typeid"}