Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -177,6 +177,15 @@
   if (Config->Optimize == 0)
     return false;
 
+  // Do not merge sections if generate a relocatable object. It makes the code
+  // simpler because we do not need to update relocations addend to reflect
+  // changes introduced by merging. Instead of that we write such "merge"
+  // sections into separate output ones and keep SHF_MERGE/SHF_STRINGS flags
+  // and sh_entsize value to be able to perform merging later during a final
+  // linking.
+  if (Config->Relocatable)
+    return false;
+
   // A mergeable section with size 0 is useless because they don't have
   // any data to merge. A mergeable string section with size 0 can be
   // argued as invalid because it doesn't end with a null character.
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -894,6 +894,10 @@
   Sections.push_back(S);
   S->OutSec = this;
   this->updateAlignment(S->Alignment);
+  // Keep sh_entsize value of the input section to be able to perform merging
+  // later during a final linking using the generated relocatable object.
+  if (Config->Relocatable && (S->getSectionHdr()->sh_flags & SHF_MERGE))
+    this->Header.sh_entsize = S->getSectionHdr()->sh_entsize;
 }
 
 // This function is called after we sort input sections
@@ -1842,8 +1846,12 @@
   // For SHF_MERGE we create different output sections for each alignment.
   // This makes each output section simple and keeps a single level mapping from
   // input to output.
+  // In case of relocatable object generation we do not try to perform merging
+  // and treat SHF_MERGE sections as regular ones, but also create different
+  // output sections for them to allow merging at final linking stage.
   uintX_t Alignment = 0;
-  if (isa<MergeInputSection<ELFT>>(C))
+  if (isa<MergeInputSection<ELFT>>(C) ||
+      (Config->Relocatable && (H->sh_flags & SHF_MERGE)))
     Alignment = std::max(H->sh_addralign, H->sh_entsize);
 
   uint32_t Type = H->sh_type;
Index: test/ELF/merge-reloc.s
===================================================================
--- /dev/null
+++ test/ELF/merge-reloc.s
@@ -0,0 +1,92 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld %t.o -r -o %t-rel
+# RUN: llvm-readobj -s -section-data %t-rel | FileCheck %s
+
+# When linker generates a relocatable object it should keep "merge"
+# sections as-is: do not merge content, do not join regular and
+# "merge" sections, do not joint "merge" sections with different
+# entry size.
+
+# CHECK:      Section {
+# CHECK:        Index:
+# CHECK:        Name: .data
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:     SHF_MERGE
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size: 12
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 4
+# CHECK-NEXT:   EntrySize: 4
+# CHECK-NEXT:   SectionData (
+# CHECK-NEXT:     0000: 42000000 42000000 42000000
+# CHECK-NEXT:   )
+# CHECK-NEXT: }
+# CHECK:      Section {
+# CHECK:        Index:
+# CHECK:        Name: .data
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:     SHF_MERGE
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size: 16
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 8
+# CHECK-NEXT:   EntrySize: 8
+# CHECK-NEXT:   SectionData (
+# CHECK-NEXT:     0000: 42000000 42000000 42000000 42000000
+# CHECK-NEXT:   )
+# CHECK-NEXT: }
+# CHECK:      Section {
+# CHECK:        Index:
+# CHECK:        Name: .data
+# CHECK-NEXT:   Type: SHT_PROGBITS
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:     SHF_WRITE
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size: 16
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 1
+# CHECK-NEXT:   EntrySize: 0
+# CHECK-NEXT:   SectionData (
+# CHECK-NEXT:     0000: 42000000 42000000 42000000 42000000
+# CHECK-NEXT:   )
+# CHECK-NEXT: }
+
+        .section        .data.1,"aM",@progbits,4
+        .align  4
+        .global foo
+foo:
+        .long   0x42
+        .long   0x42
+        .long   0x42
+
+        .section        .data.2,"aM",@progbits,8
+        .align  8
+        .global bar
+bar:
+        .long   0x42
+        .long   0x42
+        .long   0x42
+        .long   0x42
+
+        .data
+        .global gar
+zed:
+        .long   0x42
+        .long   0x42
+        .long   0x42
+        .long   0x42