Index: lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
===================================================================
--- lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -310,12 +310,14 @@
     return RISCVFPRndMode::stringToRoundingMode(Str) != RISCVFPRndMode::Invalid;
   }
 
-  bool isImmXLen() const {
+  bool isImmXLenLI() const {
     int64_t Imm;
     RISCVMCExpr::VariantKind VK;
     if (!isImm())
       return false;
     bool IsConstantImm = evaluateConstantImm(getImm(), Imm, VK);
+    if (VK == RISCVMCExpr::VK_RISCV_LO || VK == RISCVMCExpr::VK_RISCV_PCREL_LO)
+      return true;
     // Given only Imm, ensuring that the actually specified constant is either
     // a signed or unsigned 64-bit number is unfortunately impossible.
     bool IsInRange = isRV64() ? true : isInt<32>(Imm) || isUInt<32>(Imm);
@@ -782,7 +784,7 @@
   switch(Result) {
   default:
     break;
-  case Match_InvalidImmXLen:
+  case Match_InvalidImmXLenLI:
     if (isRV64()) {
       SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
       return Error(ErrorLoc, "operand must be a constant 64-bit integer");
@@ -1449,7 +1451,17 @@
   Inst.setLoc(IDLoc);
 
   if (Inst.getOpcode() == RISCV::PseudoLI) {
-    auto Reg = Inst.getOperand(0).getReg();
+    unsigned Reg = Inst.getOperand(0).getReg();
+    const MCOperand &Op1 = Inst.getOperand(1);
+    if (Op1.isExpr()) {
+      // We must have li reg, %lo(sym) or li reg, %pcrel_lo(sym) or similar.
+      // Just convert to an addi. This allows compatibility with gas.
+      emitToStreamer(Out, MCInstBuilder(RISCV::ADDI)
+                              .addReg(Reg)
+                              .addReg(RISCV::X0)
+                              .addExpr(Op1.getExpr()));
+      return false;
+    }
     int64_t Imm = Inst.getOperand(1).getImm();
     // On RV32 the immediate here can either be a signed or an unsigned
     // 32-bit number. Sign extension has to be performed to ensure that Imm
Index: lib/Target/RISCV/RISCVInstrInfo.td
===================================================================
--- lib/Target/RISCV/RISCVInstrInfo.td
+++ lib/Target/RISCV/RISCVInstrInfo.td
@@ -198,8 +198,10 @@
 }
 
 // A parameterized register class alternative to i32imm/i64imm from Target.td.
-def ixlenimm : Operand<XLenVT> {
-  let ParserMatchClass = ImmXLenAsmOperand<"">;
+def ixlenimm : Operand<XLenVT>;
+
+def ixlenimm_li : Operand<XLenVT> {
+  let ParserMatchClass = ImmXLenAsmOperand<"", "LI">;
 }
 
 // Standalone (codegen-only) immleaf patterns.
@@ -497,7 +499,7 @@
 // expanded to real instructions immediately.
 let hasSideEffects = 0, mayLoad = 0, mayStore = 0, Size = 32,
     isCodeGenOnly = 0, isAsmParserOnly = 1 in
-def PseudoLI : Pseudo<(outs GPR:$rd), (ins ixlenimm:$imm), [],
+def PseudoLI : Pseudo<(outs GPR:$rd), (ins ixlenimm_li:$imm), [],
                       "li", "$rd, $imm">;
 
 def : InstAlias<"mv $rd, $rs",   (ADDI GPR:$rd, GPR:$rs,       0)>;
Index: test/MC/RISCV/rv32i-aliases-valid.s
===================================================================
--- test/MC/RISCV/rv32i-aliases-valid.s
+++ test/MC/RISCV/rv32i-aliases-valid.s
@@ -3,10 +3,10 @@
 # RUN: llvm-mc %s -triple=riscv32 \
 # RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS %s
 # RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -riscv-no-aliases -d - \
-# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-INST %s
+# RUN:     | llvm-objdump -riscv-no-aliases -d -r - \
+# RUN:     | FileCheck -check-prefixes=CHECK-OBJ-NOALIAS,CHECK-EXPAND,CHECK-INST %s
 # RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN:     | llvm-objdump -d -r - \
 # RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS %s
 
 # The following check prefixes are used in this test:
@@ -69,6 +69,19 @@
 # CHECK-EXPAND: addi a2, zero, -1
 li x12, 0xFFFFFFFF
 
+# CHECK-EXPAND: addi a0, zero, 1110
+li a0, %lo(0x123456)
+# CHECK-OBJ-NOALIAS: addi a0, zero, 0
+# CHECK-OBJ: R_RISCV_PCREL_LO12
+li a0, %pcrel_lo(0x123456)
+
+# CHECK-OBJ-NOALIAS: addi a0, zero, 0
+# CHECK-OBJ: R_RISCV_LO12
+li a0, %lo(foo)
+# CHECK-OBJ-NOALIAS: addi a0, zero, 0
+# CHECK-OBJ: R_RISCV_PCREL_LO12
+li a0, %pcrel_lo(foo)
+
 # CHECK-INST: csrrs t4, instreth, zero
 # CHECK-ALIAS: rdinstreth t4
 rdinstreth x29
Index: test/MC/RISCV/rv64i-aliases-valid.s
===================================================================
--- test/MC/RISCV/rv64i-aliases-valid.s
+++ test/MC/RISCV/rv64i-aliases-valid.s
@@ -4,7 +4,7 @@
 # RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS %s
 # RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
 # RUN:     | llvm-objdump -riscv-no-aliases -d - \
-# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-INST %s
+# RUN:     | FileCheck -check-prefixes=CHECK-OBJ-NOALIAS,CHECK-EXPAND,CHECK-INST %s
 # RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
 # RUN:     | llvm-objdump -d - \
 # RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS %s
@@ -105,6 +105,19 @@
 # CHECK-EXPAND: addi t5, zero, -1
 li t5, 0xFFFFFFFFFFFFFFFF
 
+# CHECK-EXPAND: addi a0, zero, 1110
+li a0, %lo(0x123456)
+# CHECK-OBJ-NOALIAS: addi a0, zero, 0
+# CHECK-OBJ: R_RISCV_PCREL_LO12
+li a0, %pcrel_lo(0x123456)
+
+# CHECK-OBJ-NOALIAS: addi a0, zero, 0
+# CHECK-OBJ: R_RISCV_LO12
+li a0, %lo(foo)
+# CHECK-OBJ-NOALIAS: addi a0, zero, 0
+# CHECK-OBJ: R_RISCV_PCREL_LO12
+li a0, %pcrel_lo(foo)
+
 # CHECK-INST: subw t6, zero, ra
 # CHECK-ALIAS: negw t6, ra
 negw x31, x1