[ThinLTO/Summary] Rename anonymous globals as last action ...

... in the per-TU -O0 pipeline.
The problem is that there could be passes registered using
`addExtensionsToPM()` introducing unnamed globals.
Asan is an example, but there may be others. Building cppcheck
with `-flto=thin` and `-fsanitize=address` triggers an assertion
while we're reading bitcode (in lib/LTO), as the BitcodeReader
assumes there are no unnamed globals (because the namer has run).
Unfortunately I wasn't able to find an easy way to test this.
I added a comment in the hope nobody moves this again.

llvm-svn: 301102

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -414,11 +414,14 @@ void PassManagerBuilder::populateModulePassManager(
     else if (!GlobalExtensions->empty() || !Extensions.empty())
       MPM.add(createBarrierNoopPass());
 
-    if (PrepareForThinLTO)
-      // Rename anon globals to be able to export them in the summary.
-      MPM.add(createNameAnonGlobalPass());
-
     addExtensionsToPM(EP_EnabledOnOptLevel0, MPM);
+
+    // Rename anon globals to be able to export them in the summary.
+    // This has to be done after we add the extensions to the pass manager
+    // as there could be passes (e.g. Adddress sanitizer) which introduce
+    // new unnamed globals.
+    if (PrepareForThinLTO)
+      MPM.add(createNameAnonGlobalPass());
     return;
   }