Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -5946,7 +5946,11 @@
 
     NewVD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0),
                                                 Context, Label, 0));
-  } else if (!ExtnameUndeclaredIdentifiers.empty()) {
+  // Deferred handling of "redefine_extname" pragma.
+  } else if (!ExtnameUndeclaredIdentifiers.empty() &&
+             (NewVD->getDeclContext()->isTranslationUnit() ||
+              NewVD->isExternC()) &&
+             NewVD->hasExternalFormalLinkage()) {
     llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
       ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
     if (I != ExtnameUndeclaredIdentifiers.end()) {
@@ -7468,7 +7472,11 @@
     StringLiteral *SE = cast<StringLiteral>(E);
     NewFD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0), Context,
                                                 SE->getString(), 0));
-  } else if (!ExtnameUndeclaredIdentifiers.empty()) {
+  // Deferred handling of "redefine_extname" pragma.
+  } else if (!ExtnameUndeclaredIdentifiers.empty() &&
+             (NewFD->getDeclContext()->isTranslationUnit() ||
+              NewFD->isExternC()) &&
+             NewFD->hasExternalFormalLinkage()) {
     llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
       ExtnameUndeclaredIdentifiers.find(NewFD->getIdentifier());
     if (I != ExtnameUndeclaredIdentifiers.end()) {
Index: test/CodeGen/redefine_extname.c
===================================================================
--- test/CodeGen/redefine_extname.c
+++ test/CodeGen/redefine_extname.c
@@ -13,3 +13,14 @@
 // CHECK:   call i32 @real()
 // Check that this also works with variables names
 // CHECK:   load i32, i32* @alias
+
+// This is a case when redefenition is deferred *and* we have a local of the
+// same name. PR23923.
+#pragma redefine_extname foo bar
+int f() {
+  int foo = 0;
+  return foo;
+}
+extern int foo() { return 1; }
+// CHECK: define i32 @bar()
+