Index: include/llvm/BinaryFormat/ELFRelocs/AVR.def
===================================================================
--- include/llvm/BinaryFormat/ELFRelocs/AVR.def
+++ include/llvm/BinaryFormat/ELFRelocs/AVR.def
@@ -38,3 +38,6 @@
 ELF_RELOC(R_AVR_LDS_STS_16,           33)
 ELF_RELOC(R_AVR_PORT6,                34)
 ELF_RELOC(R_AVR_PORT5,                35)
+ELF_RELOC(R_AVR_DIFF8,                36)
+ELF_RELOC(R_AVR_DIFF16,               37)
+ELF_RELOC(R_AVR_DIFF32,               38)
Index: lib/Target/AVR/AsmParser/AVRAsmParser.cpp
===================================================================
--- lib/Target/AVR/AsmParser/AVRAsmParser.cpp
+++ lib/Target/AVR/AsmParser/AVRAsmParser.cpp
@@ -80,6 +80,8 @@
                       uint64_t const &ErrorInfo);
   bool missingFeature(SMLoc const &Loc, uint64_t const &ErrorInfo);
 
+  bool parseLiteralValues(unsigned Size, SMLoc L);
+
 public:
   AVRAsmParser(const MCSubtargetInfo &STI, MCAsmParser &Parser,
                const MCInstrInfo &MII, const MCTargetOptions &Options)
@@ -432,6 +434,11 @@
   if (ModifierKind != AVRMCExpr::VK_AVR_None) {
     Parser.Lex();
     Parser.Lex(); // Eat modifier name and parenthesis
+    // FIXME: Not support gs(foo) so just eat gs.
+    if (Parser.getTok().getString() == "gs" &&
+        Parser.getTok().getKind() == AsmToken::Identifier) {
+      Parser.Lex();
+    }
   } else {
     return Error(Parser.getTok().getLoc(), "unknown modifier");
   }
@@ -580,7 +587,35 @@
   return false;
 }
 
-bool AVRAsmParser::ParseDirective(llvm::AsmToken DirectiveID) { return true; }
+bool AVRAsmParser::ParseDirective(llvm::AsmToken DirectiveID) {
+  StringRef IDVal = DirectiveID.getIdentifier();
+  if (IDVal == ".long")
+    parseLiteralValues(8, DirectiveID.getLoc());
+  else if (IDVal == ".word")
+    parseLiteralValues(4, DirectiveID.getLoc());
+  else if (IDVal == ".short")
+    parseLiteralValues(2, DirectiveID.getLoc());
+  else if (IDVal == ".byte")
+    parseLiteralValues(1, DirectiveID.getLoc());
+  return true;
+}
+
+bool AVRAsmParser::parseLiteralValues(unsigned Size, SMLoc L) {
+  MCAsmParser &Parser = getParser();
+  if (Parser.getTok().getKind() == AsmToken::Identifier &&
+      Parser.getLexer().peekTok().getKind() == AsmToken::LParen) {
+    const MCExpr *Value;
+    return Parser.parseExpression(Value);
+  }
+  auto parseOne = [&]() -> bool {
+    const MCExpr *Value;
+    if (Parser.parseExpression(Value))
+      return true;
+    Parser.getStreamer().EmitValue(Value, Size, L);
+    return false;
+  };
+  return (parseMany(parseOne));
+}
 
 extern "C" void LLVMInitializeAVRAsmParser() {
   RegisterMCAsmParser<AVRAsmParser> X(getTheAVRTarget());
Index: lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
===================================================================
--- lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
+++ lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
@@ -423,6 +423,9 @@
 
       {"fixup_sym_diff", 0, 32, 0},
       {"fixup_16_ldst", 0, 16, 0},
+      {"fixup_diff8", 0, 8, 0},
+      {"fixup_diff16", 0, 16, 0},
+      {"fixup_diff32", 0, 32, 0},
 
       {"fixup_lds_sts_16", 0, 16, 0},
 
Index: lib/Target/AVR/MCTargetDesc/AVRELFObjectWriter.cpp
===================================================================
--- lib/Target/AVR/MCTargetDesc/AVRELFObjectWriter.cpp
+++ lib/Target/AVR/MCTargetDesc/AVRELFObjectWriter.cpp
@@ -107,6 +107,12 @@
     return ELF::R_AVR_SYM_DIFF;
   case AVR::fixup_16_ldst:
     return ELF::R_AVR_16_LDST;
+  case AVR::fixup_diff8:
+    return ELF::R_AVR_DIFF8;
+  case AVR::fixup_diff16:
+    return ELF::R_AVR_DIFF16;
+  case AVR::fixup_diff32:
+    return ELF::R_AVR_DIFF32;
   case AVR::fixup_lds_sts_16:
     return ELF::R_AVR_LDS_STS_16;
   case AVR::fixup_port6:
Index: lib/Target/AVR/MCTargetDesc/AVRFixupKinds.h
===================================================================
--- lib/Target/AVR/MCTargetDesc/AVRFixupKinds.h
+++ lib/Target/AVR/MCTargetDesc/AVRFixupKinds.h
@@ -119,6 +119,9 @@
   /// Is the only stateful fixup. We do not support it yet.
   fixup_sym_diff,
   fixup_16_ldst,
+  fixup_diff8,
+  fixup_diff16,
+  fixup_diff32,
 
   fixup_lds_sts_16,
 
Index: test/MC/AVR/relocations.s
===================================================================
--- test/MC/AVR/relocations.s
+++ test/MC/AVR/relocations.s
@@ -73,3 +73,33 @@
 
 ; CHECK-NEXT: R_AVR_HH8_LDI_PM_NEG
 ldi r25, -pm_hh8(foo)
+
+; CHECK-NEXT: R_AVR_LO8_LDI_GS
+ldi r17, lo8(gs(foo))
+
+; CHECK-NEXT: R_AVR_HI8_LDI_GS
+ldi r18, hi8(gs(foo))
+
+; CHECK-NEXT: R_AVR_16_PM
+.short foo
+
+; CHECK-NEXT: R_AVR_8
+.byte foo
+
+; CHECK-NEXT: R_AVR_8_LO8
+.byte lo8(foo)
+
+; CHECK-NEXT: R_AVR_8_HI8
+.byte hi8(foo)
+
+; CHECK-NEXT: R_AVR_8_HLO8
+.byte hlo8(foo)
+
+; CHECK-NEXT: R_AVR_DIFF8
+.byte foo - bar
+
+; CHECK-NEXT: R_AVR_DIFF16
+.word foo - bar
+
+; CHECK-NEXT: R_AVR_DIFF32
+.long foo - bar