save irrelevant change for the next PR to make this one focused

Author: mingmingl-llvm

llvm/lib/CodeGen/StaticDataAnnotator.cpp

@@ -78,8 +78,19 @@ bool StaticDataAnnotator::runOnModule(Module &M) {
     if (!llvm::memprof::IsAnnotationOK(GV))
       continue;
 
+    // The implementation below assumes prior passes don't set section prefixes,
+    // and specifically do 'assign' rather than 'update'. So report error if a
+    // section prefix is already set.
+    if (auto maybeSectionPrefix = GV.getSectionPrefix();
+        maybeSectionPrefix && !maybeSectionPrefix->empty())
+      llvm::report_fatal_error("Global variable " + GV.getName() +
+                               " already has a section prefix " +
+                               *maybeSectionPrefix);
+
     StringRef SectionPrefix = SDPI->getConstantSectionPrefix(&GV, PSI);
-    // setSectionPrefix returns true if the section prefix is changed.
+    if (SectionPrefix.empty())
+      continue;
+
     Changed |= GV.setSectionPrefix(SectionPrefix);
   }