Index: lld/ELF/InputFiles.cpp
===================================================================
--- lld/ELF/InputFiles.cpp
+++ lld/ELF/InputFiles.cpp
@@ -1155,9 +1155,12 @@
       if ((sym->symbolKind == Symbol::LazyArchiveKind &&
            !cast<ArchiveFile>(sym->file)->parsed) ||
           (sym->symbolKind == Symbol::LazyObjectKind &&
-           cast<LazyObjFile>(sym->file)->extracted))
+           cast<LazyObjFile>(sym->file)->extracted)) {
         sym->replace(und);
-      else
+        // Prevent LTO from internalizing the symbol in case there is a
+        // reference to this symbol from this file.
+        sym->isUsedInRegularObj = true;
+      } else
         sym->resolve(und);
       continue;
     }
Index: lld/test/ELF/lto/comdat-mixed-archive.test
===================================================================
--- /dev/null
+++ lld/test/ELF/lto/comdat-mixed-archive.test
@@ -0,0 +1,58 @@
+REQUIRES: x86
+
+;; This checks a case when an archive contains a bitcode and a regular object
+;; files, and a comdat symbol is defined and used in both of them. Previously,
+;; lld could lose the flag that the symbol is used in a regular object file
+;; which led to the LTO backend internalizing the symbol and the linker
+;; reporting an "undefined symbol" error.
+
+;; In this test, group "foo" in "obj.o" is rejected in favor of "bc.o" but we
+;; need to prevent LTO from internalizing "foo" as there is still a reference
+;; from outside the group in "obj.o".
+
+RUN: rm -rf %t.dir
+RUN: split-file %s %t.dir
+RUN: cd %t.dir
+
+RUN: llvm-mc -filetype=obj -triple=x86_64 start.s -o start.o
+RUN: llvm-mc -filetype=obj -triple=x86_64 obj.s -o obj.o
+RUN: llvm-as bc.ll -o bc.o
+RUN: llvm-ar rc lib.a obj.o bc.o
+RUN: ld.lld start.o lib.a -o /dev/null
+
+;--- start.s
+  .global _start, baz
+_start:
+  call baz
+
+;--- obj.s
+  .weak foo
+  .global bar
+
+  .section .text.foo,"axG",@progbits,foo,comdat
+foo:
+  ret
+
+  .section .text.bar,"ax",@progbits
+bar:
+  call foo
+
+;--- bc.ll
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+$foo = comdat any
+
+declare void @bar()
+
+;; Note. "foo" is defined after declaring "bar" so that loading the regular
+;; object file "obj.o" is triggered before processing the definition of "foo".
+define linkonce_odr void @foo() comdat {
+  ret void
+}
+
+define void @baz() {
+  call void @foo()
+  call void @bar()
+  ret void
+}