Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -256,7 +256,11 @@
   // dedup'ed section groups by their signatures. For the -r, we want to pass
   // through all SHT_GROUP sections without merging them because merging them
   // creates broken section contents.
-  if (IS->Type == SHT_GROUP) {
+  // We also do not merge any SHF_GROUP sections with any others. If we would do
+  // that we either end up with multiple SHT_GROUP sections containing the
+  // same output section or with situation when SHF_GROUP section is merged with
+  // regular section with the same name. Both cases are semantically incorrect.
+  if (IS->Type == SHT_GROUP || (IS->Flags & SHF_GROUP)) {
     addSection(IS, OutsecName, nullptr);
     return;
   }
Index: test/ELF/relocatable-comdat2.s
===================================================================
--- test/ELF/relocatable-comdat2.s
+++ test/ELF/relocatable-comdat2.s
@@ -0,0 +1,35 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld -r %t.o -o %t
+# RUN: llvm-readobj -elf-section-groups -s %t | FileCheck %s
+
+## Check .foo was not merged.
+# CHECK: Sections [
+# CHECK:  Name: .foo
+# CHECK:  Name: .foo
+# CHECK:  Name: .foo
+
+# CHECK:      Groups {
+# CHECK-NEXT:   Group {
+# CHECK-NEXT:     Name: .group
+# CHECK-NEXT:     Index: 2
+# CHECK-NEXT:     Type: COMDAT
+# CHECK-NEXT:     Signature: bar
+# CHECK-NEXT:     Section(s) in group [
+# CHECK-NEXT:       .foo (3)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Group {
+# CHECK-NEXT:     Name: .group
+# CHECK-NEXT:     Index: 4
+# CHECK-NEXT:     Type: COMDAT
+# CHECK-NEXT:     Signature: zed
+# CHECK-NEXT:     Section(s) in group [
+# CHECK-NEXT:       .foo (5)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:   }
+# CHECK-NEXT: }
+
+.section .foo,"axG",@progbits,bar,comdat
+.section .foo,"axG",@progbits,zed,comdat
+.section .foo,"ax",@progbits