Index: include/llvm/BinaryFormat/ELFRelocs/AVR.def
===================================================================
--- include/llvm/BinaryFormat/ELFRelocs/AVR.def
+++ include/llvm/BinaryFormat/ELFRelocs/AVR.def
@@ -33,8 +33,9 @@
 ELF_RELOC(R_AVR_8_LO8,                27)
 ELF_RELOC(R_AVR_8_HI8,                28)
 ELF_RELOC(R_AVR_8_HLO8,               29)
-ELF_RELOC(R_AVR_SYM_DIFF,             30)
-ELF_RELOC(R_AVR_16_LDST,              31)
+ELF_RELOC(R_AVR_DIFF8,                30)
+ELF_RELOC(R_AVR_DIFF16,               31)
+ELF_RELOC(R_AVR_DIFF32,               32)
 ELF_RELOC(R_AVR_LDS_STS_16,           33)
 ELF_RELOC(R_AVR_PORT6,                34)
 ELF_RELOC(R_AVR_PORT5,                35)
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)
@@ -404,11 +406,14 @@
   size_t ReadCount = Parser.getLexer().peekTokens(tokens);
 
   if (ReadCount == 2) {
-    if (tokens[0].getKind() == AsmToken::Identifier &&
-        tokens[1].getKind() == AsmToken::LParen) {
+    if ((tokens[0].getKind() == AsmToken::Identifier &&
+         tokens[1].getKind() == AsmToken::LParen) ||
+        (tokens[0].getKind() == AsmToken::LParen &&
+         tokens[1].getKind() == AsmToken::Minus)) {
 
       AsmToken::TokenKind CurTok = Parser.getLexer().getKind();
-      if (CurTok == AsmToken::Minus) {
+      if (CurTok == AsmToken::Minus ||
+          tokens[1].getKind() == AsmToken::Minus) {
         isNegated = true;
       } else {
         assert(CurTok == AsmToken::Plus);
@@ -416,7 +421,8 @@
       }
 
       // Eat the sign
-      Parser.Lex();
+      if (CurTok == AsmToken::Minus || CurTok == AsmToken::Plus)
+        Parser.Lex();
     }
   }
 
@@ -432,14 +438,32 @@
   if (ModifierKind != AVRMCExpr::VK_AVR_None) {
     Parser.Lex();
     Parser.Lex(); // Eat modifier name and parenthesis
+    if (Parser.getTok().getString() == "gs" &&
+        Parser.getTok().getKind() == AsmToken::Identifier) {
+      std::string GSModName = ModifierName.str() += "_gs";
+      ModifierKind = AVRMCExpr::getKindByName(GSModName.c_str());
+      if (ModifierKind != AVRMCExpr::VK_AVR_None)
+        Parser.Lex(); // Eat gs modifier name
+    }
   } else {
     return Error(Parser.getTok().getLoc(), "unknown modifier");
   }
 
+  if (tokens[1].getKind() == AsmToken::Minus) {
+    Parser.Lex();
+    assert(Parser.getTok().getKind() == AsmToken::LParen);
+    Parser.Lex(); // Eat the sign and parenthesis
+  }
+
   MCExpr const *InnerExpression;
   if (getParser().parseExpression(InnerExpression))
     return true;
 
+  if (tokens[1].getKind() == AsmToken::Minus) {
+    assert(Parser.getTok().getKind() == AsmToken::RParen);
+    Parser.Lex(); // Eat closing parenthesis
+  }
+
   // If we have a modifier wrap the inner expression
   assert(Parser.getTok().getKind() == AsmToken::RParen);
   Parser.Lex(); // Eat closing parenthesis
@@ -580,7 +604,50 @@
   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) {
+    StringRef ModifierName = Parser.getTok().getString();
+    AVRMCExpr::VariantKind ModifierKind =
+        AVRMCExpr::getKindByName(ModifierName.str().c_str());
+    if (ModifierKind != AVRMCExpr::VK_AVR_None) {
+      Parser.Lex();
+      Parser.Lex(); // Eat the modifier and parenthesis
+    } else {
+      return Error(Parser.getTok().getLoc(), "unknown modifier");
+    }
+    const MCExpr *InnerExpression;
+    if (Parser.parseExpression(InnerExpression))
+      return true;
+    // FIXME: not supports Modifier, for example: .byte lo8(foo)
+    // Does it need to re-architecture ParseDirective for adding parameter
+    // OperandVector Operands?
+    Parser.getStreamer().EmitValue(InnerExpression, Size, L);
+    return false;
+  }
+  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
@@ -266,13 +266,17 @@
     break;
   case AVR::fixup_lo8_ldi:
   case AVR::fixup_lo8_ldi_pm:
-    if (Kind == AVR::fixup_lo8_ldi_pm) adjust::pm(Value);
+  case AVR::fixup_lo8_ldi_gs:
+    if (Kind == AVR::fixup_lo8_ldi_pm || Kind == AVR::fixup_lo8_ldi_gs)
+      adjust::pm(Value);
 
     adjust::ldi::lo8(Size, Fixup, Value, Ctx);
     break;
   case AVR::fixup_hi8_ldi:
   case AVR::fixup_hi8_ldi_pm:
-    if (Kind == AVR::fixup_hi8_ldi_pm) adjust::pm(Value);
+  case AVR::fixup_hi8_ldi_gs:
+    if (Kind == AVR::fixup_hi8_ldi_pm || Kind == AVR::fixup_hi8_ldi_gs)
+      adjust::pm(Value);
 
     adjust::ldi::hi8(Size, Fixup, Value, Ctx);
     break;
@@ -421,8 +425,9 @@
       {"fixup_8_hi8", 0, 8, 0},
       {"fixup_8_hlo8", 0, 8, 0},
 
-      {"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
@@ -39,20 +39,34 @@
                                           const MCValue &Target,
                                           const MCFixup &Fixup,
                                           bool IsPCRel) const {
+  MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
   switch ((unsigned) Fixup.getKind()) {
   case FK_Data_1:
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_AVR_8;
+    }
+  case AVR::fixup_8:
+    return ELF::R_AVR_8;
   case FK_Data_4:
     llvm_unreachable("unsupported relocation type");
   case FK_Data_2:
-    return ELF::R_AVR_16_PM;
+    switch (Modifier) {
+    default:
+      llvm_unreachable("Unsupported Modifier");
+    case MCSymbolRefExpr::VK_None:
+      return ELF::R_AVR_16;
+    }
+  case AVR::fixup_16:
+    return ELF::R_AVR_16;
   case AVR::fixup_32:
     return ELF::R_AVR_32;
   case AVR::fixup_7_pcrel:
     return ELF::R_AVR_7_PCREL;
   case AVR::fixup_13_pcrel:
     return ELF::R_AVR_13_PCREL;
-  case AVR::fixup_16:
-    return ELF::R_AVR_16;
   case AVR::fixup_16_pm:
     return ELF::R_AVR_16_PM;
   case AVR::fixup_lo8_ldi:
@@ -95,18 +109,18 @@
     return ELF::R_AVR_LO8_LDI_GS;
   case AVR::fixup_hi8_ldi_gs:
     return ELF::R_AVR_HI8_LDI_GS;
-  case AVR::fixup_8:
-    return ELF::R_AVR_8;
   case AVR::fixup_8_lo8:
     return ELF::R_AVR_8_LO8;
   case AVR::fixup_8_hi8:
     return ELF::R_AVR_8_HI8;
   case AVR::fixup_8_hlo8:
     return ELF::R_AVR_8_HLO8;
-  case AVR::fixup_sym_diff:
-    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
@@ -117,8 +117,9 @@
 
   /// Fixup to calculate the difference between two symbols.
   /// 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: lib/Target/AVR/MCTargetDesc/AVRMCExpr.h
===================================================================
--- lib/Target/AVR/MCTargetDesc/AVRMCExpr.h
+++ lib/Target/AVR/MCTargetDesc/AVRMCExpr.h
@@ -30,7 +30,11 @@
 
     VK_AVR_PM_LO8, ///< Corresponds to `pm_lo8()`.
     VK_AVR_PM_HI8, ///< Corresponds to `pm_hi8()`.
-    VK_AVR_PM_HH8  ///< Corresponds to `pm_hh8()`.
+    VK_AVR_PM_HH8, ///< Corresponds to `pm_hh8()`.
+
+    VK_AVR_LO8_GS, ///< Corresponds to `lo8(gs())`.
+    VK_AVR_HI8_GS, ///< Corresponds to `hi8(gs())`.
+    VK_AVR_GS, ///< Corresponds to `gs()`.
   };
 
 public:
Index: lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp
===================================================================
--- lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp
+++ lib/Target/AVR/MCTargetDesc/AVRMCExpr.cpp
@@ -29,6 +29,9 @@
 
     {"pm_lo8", AVRMCExpr::VK_AVR_PM_LO8}, {"pm_hi8", AVRMCExpr::VK_AVR_PM_HI8},
     {"pm_hh8", AVRMCExpr::VK_AVR_PM_HH8},
+
+    {"lo8_gs", AVRMCExpr::VK_AVR_LO8_GS}, {"hi8_gs", AVRMCExpr::VK_AVR_HI8_GS},
+    {"gs", AVRMCExpr::VK_AVR_GS},
 };
 
 } // end of anonymous namespace
@@ -118,6 +121,15 @@
   case AVRMCExpr::VK_AVR_PM_HH8:
     Value >>= 17;
     break;
+  case AVRMCExpr::VK_AVR_LO8_GS:
+    Value >>= 1;
+    break;
+  case AVRMCExpr::VK_AVR_HI8_GS:
+    Value >>= 9;
+    break;
+  case AVRMCExpr::VK_AVR_GS:
+    Value >>= 1;
+    break;
 
   case AVRMCExpr::VK_AVR_None:
     llvm_unreachable("Uninitialized expression.");
@@ -151,6 +163,15 @@
   case VK_AVR_PM_HH8:
     Kind = isNegated() ? AVR::fixup_hh8_ldi_pm_neg : AVR::fixup_hh8_ldi_pm;
     break;
+  case VK_AVR_LO8_GS:
+    Kind = AVR::fixup_lo8_ldi_gs;
+    break;
+  case VK_AVR_HI8_GS:
+    Kind = AVR::fixup_hi8_ldi_gs;
+    break;
+  case VK_AVR_GS:
+    Kind = AVR::fixup_16_pm;
+    break;
 
   case VK_AVR_None:
     llvm_unreachable("Uninitialized expression");
Index: test/MC/AVR/relocations.s
===================================================================
--- test/MC/AVR/relocations.s
+++ test/MC/AVR/relocations.s
@@ -2,6 +2,10 @@
 
 ; CHECK: RELOCATION RECORDS FOR
 
+; CHECK: RELOCATION RECORDS BAR
+bar:
+  jmp bar
+
 ; CHECK-NEXT: R_AVR_LDI SYMBOL+3
 ldi r21, SYMBOL+3
 
@@ -34,27 +38,32 @@
 
 ; CHECK-NEXT: R_AVR_LO8_LDI_NEG abc
 ldi r16, -lo8(abc)
+ldi r16, lo8(-(abc))
 
 ; CHECK-NEXT: R_AVR_HI8_LDI_NEG abc
 ldi r16, -hi8(abc)
+ldi r16, hi8(-(abc))
 
 ; CHECK-NEXT: R_AVR_HH8_LDI foo
 ldi r16, hh8(foo)
 
 ; CHECK-NEXT: R_AVR_HH8_LDI_NEG foo
 ldi r16, -hh8(foo)
+ldi r16, hh8(-(foo))
 
 ; CHECK-NEXT: R_AVR_HH8_LDI foo
 ldi r24, hlo8(foo)
 
 ; CHECK-NEXT: R_AVR_HH8_LDI_NEG foo
 ldi r24, -hlo8(foo)
+ldi r24, hlo8(-(foo))
 
 ; CHECK-NEXT: R_AVR_MS8_LDI bar
 ldi r24, hhi8(bar)
 
 ; CHECK-NEXT: R_AVR_MS8_LDI_NEG bar
 ldi r24, -hhi8(bar)
+ldi r24, hhi8(-(bar))
 
 ; CHECK-NEXT: R_AVR_LO8_LDI_PM foo
 ldi r17, pm_lo8(foo)
@@ -67,9 +76,45 @@
 
 ; CHECK-NEXT: R_AVR_LO8_LDI_PM_NEG
 ldi r25, -pm_lo8(foo)
+ldi r25, pm_lo8(-(foo))
 
 ; CHECK-NEXT: R_AVR_HI8_LDI_PM_NEG
 ldi r25, -pm_hi8(foo)
+ldi r25, pm_hi8(-(foo))
 
 ; CHECK-NEXT: R_AVR_HH8_LDI_PM_NEG
 ldi r25, -pm_hh8(foo)
+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
+.short foo
+
+; CHECK-NEXT: R_AVR_16_PM
+.short gs(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