Index: lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
@@ -102,6 +102,13 @@
     if (!isIntN(16, Value) && Ctx)
       Ctx->FatalError(Fixup.getLoc(), "out of range PC16 fixup");
     break;
+  case Mips::fixup_Mips_PC18_S3:
+    // Forcing a signed division because Value can be negative.
+    Value = (int64_t)Value / 4;
+    // We now check if Value can be encoded as a 18-bit signed immediate.
+    if (!isIntN(18, Value) && Ctx)
+      Ctx->FatalError(Fixup.getLoc(), "out of range PC18 fixup");
+    break;
   case Mips::fixup_Mips_PC19_S2:
     // Forcing a signed division because Value can be negative.
     Value = (int64_t)Value / 4;
@@ -236,6 +243,7 @@
     { "fixup_Mips_GOT_LO16",     0,     16,   0 },
     { "fixup_Mips_CALL_HI16",    0,     16,   0 },
     { "fixup_Mips_CALL_LO16",    0,     16,   0 },
+    { "fixup_Mips_PC18_S3",      0,     18,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_Mips_PC19_S2",      0,     19,   MCFixupKindInfo::FKF_IsPCRel },
     { "fixup_MICROMIPS_26_S1",   0,     26,   0 },
     { "fixup_MICROMIPS_HI16",    0,     16,   0 },
Index: lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
@@ -193,6 +193,9 @@
   case Mips::fixup_MICROMIPS_TLS_TPREL_LO16:
     Type = ELF::R_MICROMIPS_TLS_TPREL_LO16;
     break;
+  case Mips::fixup_Mips_PC18_S3:
+    Type = ELF::R_MIPS_PC18_S3;
+    break;
   case Mips::fixup_Mips_PC19_S2:
     Type = ELF::R_MIPS_PC19_S2;
     break;
Index: lib/Target/Mips/MCTargetDesc/MipsFixupKinds.h
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsFixupKinds.h
+++ lib/Target/Mips/MCTargetDesc/MipsFixupKinds.h
@@ -128,6 +128,9 @@
     // resulting in - R_MIPS_CALL_LO16
     fixup_Mips_CALL_LO16,
 
+    // resulting in - R_MIPS_PC18_S3
+    fixup_Mips_PC18_S3,
+
     // resulting in - R_MIPS_PC19_S2
     fixup_Mips_PC19_S2,
 
Index: lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
@@ -632,11 +632,21 @@
 MipsMCCodeEmitter::getSimm18Lsl3Encoding(const MCInst &MI, unsigned OpNo,
                                          SmallVectorImpl<MCFixup> &Fixups,
                                          const MCSubtargetInfo &STI) const {
-  assert(MI.getOperand(OpNo).isImm());
-  // The immediate is encoded as 'immediate << 3'.
-  unsigned Res = getMachineOpValue(MI, MI.getOperand(OpNo), Fixups, STI);
-  assert((Res & 7) == 0);
-  return Res >> 3;
+  const MCOperand &MO = MI.getOperand(OpNo);
+  if (MO.isImm()) {
+    // The immediate is encoded as 'immediate << 3'.
+    unsigned Res = getMachineOpValue(MI, MI.getOperand(OpNo), Fixups, STI);
+    assert((Res & 7) == 0);
+    return Res >> 3;
+  }
+
+  assert(MO.isExpr() &&
+         "getSimm18Lsl2Encoding expects only expressions or an immediate");
+
+  const MCExpr *Expr = MO.getExpr();
+  Fixups.push_back(MCFixup::Create(0, Expr,
+                                   MCFixupKind(Mips::fixup_Mips_PC18_S3)));
+  return 0;
 }
 
 #include "MipsGenMCCodeEmitter.inc"
Index: lib/Target/Mips/MipsInstrInfo.td
===================================================================
--- lib/Target/Mips/MipsInstrInfo.td
+++ lib/Target/Mips/MipsInstrInfo.td
@@ -344,6 +344,7 @@
 def simm18_lsl3 : Operand<i32> {
   let EncoderMethod = "getSimm18Lsl3Encoding";
   let DecoderMethod = "DecodeSimm18Lsl3";
+  let ParserMatchClass = MipsPCRelImmOperand;
 }
 
 def simm20      : Operand<i32> {
Index: test/MC/Mips/mips64r6/relocations.s
===================================================================
--- test/MC/Mips/mips64r6/relocations.s
+++ test/MC/Mips/mips64r6/relocations.s
@@ -11,6 +11,10 @@
 # CHECK-FIXUP:                               # fixup A - offset: 0,
 # CHECK-FIXUP:                                 value: bar,
 # CHECK-FIXUP:                                 kind: fixup_Mips_PC19_S2
+# CHECK-FIXUP: ldpc    $2, bar               # encoding: [A,A,0b010110AA,0xec]
+# CHECK-FIXUP:                               # fixup A - offset: 0,
+# CHECK-FIXUP:                                 value: bar,
+# CHECK-FIXUP:                                 kind: fixup_Mips_PC18_S3
 # CHECK-FIXUP: lwpc    $2, bar               # encoding: [A,A,0b01001AAA,0xec]
 # CHECK-FIXUP:                               #   fixup A - offset: 0,
 # CHECK-FIXUP:                                value: bar,
@@ -24,11 +28,13 @@
 #------------------------------------------------------------------------------
 # CHECK-ELF: Relocations [
 # CHECK-ELF:     0x0 R_MIPS_PC19_S2 bar 0x0
-# CHECK-ELF:     0x4 R_MIPS_PC19_S2 bar 0x0
+# CHECK-ELF:     0x4 R_MIPS_PC18_S3 bar 0x0
 # CHECK-ELF:     0x8 R_MIPS_PC19_S2 bar 0x0
+# CHECK-ELF:     0xC R_MIPS_PC19_S2 bar 0x0
 # CHECK-ELF: ]
 
     addiupc   $2,bar
+    ldpc      $2,bar
     lwpc      $2,bar
     lwupc     $2,bar