IRMover: Avoid accidentally mapping types from the destination module (PR30799)

During Module linking, it's possible for SrcM->getIdentifiedStructTypes();
to return types that are actually defined in the destination module
(DstM). Depending on how the bitcode file was read,
getIdentifiedStructTypes() might do a walk over all values, including
metadata nodes, looking for types. In my case, a debug info metadata
node was shared between the two modules, and it referred to a type
defined in the destination module (see test case).

Differential Revision: https://reviews.llvm.org/D26212

llvm-svn: 287353

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index 18389143124..4866ed2433d 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -701,6 +701,14 @@ void IRLinker::computeTypeMapping() {
     if (!ST->hasName())
       continue;
 
+    if (TypeMap.DstStructTypesSet.hasType(ST)) {
+      // This is actually a type from the destination module.
+      // getIdentifiedStructTypes() can have found it by walking debug info
+      // metadata nodes, some of which get linked by name when ODR Type Uniquing
+      // is enabled on the Context, from the source to the destination module.
+      continue;
+    }
+
     // Check to see if there is a dot in the name followed by a digit.
     size_t DotPos = ST->getName().rfind('.');
     if (DotPos == 0 || DotPos == StringRef::npos ||