diff --git a/llvm/include/llvm/Transforms/IPO/FunctionImport.h b/llvm/include/llvm/Transforms/IPO/FunctionImport.h
--- a/llvm/include/llvm/Transforms/IPO/FunctionImport.h
+++ b/llvm/include/llvm/Transforms/IPO/FunctionImport.h
@@ -136,6 +136,10 @@
 /// \p ModuleToDefinedGVSummaries contains for each Module a map
 /// (GUID -> Summary) for every global defined in the module.
 ///
+/// \p isPrevailing is a callback that will be called with a global value's GUID
+/// and summary and should return whether the module corresponding to the
+/// summary contains the linker-prevailing copy of that value.
+///
 /// \p ImportLists will be populated with an entry for every Module we are
 /// importing into. This entry is itself a map that can be passed to
 /// FunctionImporter::importFunctions() above (see description there).
@@ -153,6 +157,10 @@
 
 /// Compute all the imports for the given module using the Index.
 ///
+/// \p isPrevailing is a callback that will be called with a global value's GUID
+/// and summary and should return whether the module corresponding to the
+/// summary contains the linker-prevailing copy of that value.
+///
 /// \p ImportList will be populated with a map that can be passed to
 /// FunctionImporter::importFunctions() above (see description there).
 void ComputeCrossModuleImportForModule(