diff --git a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
--- a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -246,6 +246,7 @@
 
   static bool classifySymbolRef(const MCExpr *Expr,
                                 RISCVMCExpr::VariantKind &Kind);
+  static bool isSymbolDiff(const MCExpr *Expr);
 
   RISCVAsmParser(const MCSubtargetInfo &STI, MCAsmParser &Parser,
                  const MCInstrInfo &MII, const MCTargetOptions &Options)
@@ -562,8 +563,12 @@
       return true;
     // Given only Imm, ensuring that the actually specified constant is either
     // a signed or unsigned 64-bit number is unfortunately impossible.
-    return IsConstantImm && VK == RISCVMCExpr::VK_RISCV_None &&
-           (isRV64Imm() || (isInt<32>(Imm) || isUInt<32>(Imm)));
+    if (IsConstantImm) {
+      return VK == RISCVMCExpr::VK_RISCV_None &&
+             (isRV64Imm() || (isInt<32>(Imm) || isUInt<32>(Imm)));
+    }
+
+    return RISCVAsmParser::isSymbolDiff(getImm());
   }
 
   bool isUImmLog2XLen() const {
@@ -2547,6 +2552,16 @@
   return false;
 }
 
+bool RISCVAsmParser::isSymbolDiff(const MCExpr *Expr) {
+  MCValue Res;
+  MCFixup Fixup;
+  if (Expr->evaluateAsRelocatable(Res, nullptr, &Fixup)) {
+    return Res.getRefKind() == RISCVMCExpr::VK_RISCV_None && Res.getSymA() &&
+           Res.getSymB();
+  }
+  return false;
+}
+
 bool RISCVAsmParser::ParseDirective(AsmToken DirectiveID) {
   // This returns false if this function recognizes the directive
   // regardless of whether it is successfully handles or reports an
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
@@ -53,6 +53,7 @@
       // name                      offset bits  flags
       {"fixup_riscv_hi20", 12, 20, 0},
       {"fixup_riscv_lo12_i", 20, 12, 0},
+      {"fixup_riscv_12_i", 20, 12, 0},
       {"fixup_riscv_lo12_s", 0, 32, 0},
       {"fixup_riscv_pcrel_hi20", 12, 20,
        MCFixupKindInfo::FKF_IsPCRel | MCFixupKindInfo::FKF_IsTarget},
@@ -421,6 +422,12 @@
   case RISCV::fixup_riscv_pcrel_lo12_i:
   case RISCV::fixup_riscv_tprel_lo12_i:
     return Value & 0xfff;
+  case RISCV::fixup_riscv_12_i:
+    if (!isInt<12>(Value)) {
+      Ctx.reportError(Fixup.getLoc(),
+                      "operand must be a constant 12-bit integer");
+    }
+    return Value & 0xfff;
   case RISCV::fixup_riscv_lo12_s:
   case RISCV::fixup_riscv_pcrel_lo12_s:
   case RISCV::fixup_riscv_tprel_lo12_s:
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVFixupKinds.h b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVFixupKinds.h
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVFixupKinds.h
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVFixupKinds.h
@@ -20,6 +20,8 @@
   fixup_riscv_hi20 = FirstTargetFixupKind,
   // 12-bit fixup corresponding to %lo(foo) for instructions like addi
   fixup_riscv_lo12_i,
+  // 12-bit fixup corresponding to foo-bar for instructions like addi
+  fixup_riscv_12_i,
   // 12-bit fixup corresponding to %lo(foo) for the S-type store instructions
   fixup_riscv_lo12_s,
   // 20-bit fixup corresponding to %pcrel_hi(foo) for instructions like auipc
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
@@ -448,6 +448,8 @@
       FixupKind = RISCV::fixup_riscv_rvc_jump;
     } else if (MIFrm == RISCVII::InstFormatCB) {
       FixupKind = RISCV::fixup_riscv_rvc_branch;
+    } else if (MIFrm == RISCVII::InstFormatI) {
+      FixupKind = RISCV::fixup_riscv_12_i;
     }
   }
 
diff --git a/llvm/test/MC/RISCV/fixups-invalid.s b/llvm/test/MC/RISCV/fixups-invalid.s
--- a/llvm/test/MC/RISCV/fixups-invalid.s
+++ b/llvm/test/MC/RISCV/fixups-invalid.s
@@ -5,3 +5,11 @@
 
 .byte foo   # CHECK: [[@LINE]]:7: error: 1-byte data relocations not supported
 .2byte foo  # CHECK: [[@LINE]]:8: error: 2-byte data relocations not supported
+
+# Test that using li with a symbol difference constant rejects values that
+# cannot fit in a signed 12-bit integer.
+.Lbuf: .skip (1 << 11)
+.Lbuf_end:
+.equ CONST, .Lbuf_end - .Lbuf
+# CHECK: error: operand must be a constant 12-bit integer
+li a0, CONST
diff --git a/llvm/test/MC/RISCV/rv32i-aliases-valid.s b/llvm/test/MC/RISCV/rv32i-aliases-valid.s
--- a/llvm/test/MC/RISCV/rv32i-aliases-valid.s
+++ b/llvm/test/MC/RISCV/rv32i-aliases-valid.s
@@ -1,7 +1,7 @@
 # RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases \
-# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-INST %s
+# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-INST,CHECK-ASM-NOALIAS %s
 # RUN: llvm-mc %s -triple=riscv32 \
-# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS %s
+# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS,CHECK-ASM %s
 # RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
 # RUN:     | llvm-objdump -M no-aliases -d -r - \
 # RUN:     | FileCheck -check-prefixes=CHECK-OBJ-NOALIAS,CHECK-EXPAND,CHECK-INST %s
@@ -17,6 +17,10 @@
 # Needed for testing valid %pcrel_lo expressions
 .Lpcrel_hi0: auipc a0, %pcrel_hi(foo)
 
+# Needed for testing li with a symbol difference
+.Lbuf: .skip 8
+.Lbuf_end:
+
 # CHECK-INST: addi a0, zero, 0
 # CHECK-ALIAS: li a0, 0
 li x10, 0
@@ -103,6 +107,12 @@
 # CHECK-EXPAND: addi a0, a0, 801
 li a0, CONST
 
+.equ CONST, .Lbuf_end - .Lbuf
+# CHECK-ASM: li a0, CONST
+# CHECK-ASM-NOALIAS: addi a0, zero, CONST
+# CHECK-OBJ-NOALIAS: addi a0, zero, 8
+li a0, CONST
+
 # CHECK-INST: csrrs t4, instreth, zero
 # CHECK-ALIAS: rdinstreth t4
 rdinstreth x29
diff --git a/llvm/test/MC/RISCV/rv64i-aliases-valid.s b/llvm/test/MC/RISCV/rv64i-aliases-valid.s
--- a/llvm/test/MC/RISCV/rv64i-aliases-valid.s
+++ b/llvm/test/MC/RISCV/rv64i-aliases-valid.s
@@ -1,7 +1,7 @@
 # RUN: llvm-mc %s -triple=riscv64 -riscv-no-aliases \
-# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-INST %s
+# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-INST,CHECK-ASM-NOALIAS %s
 # RUN: llvm-mc %s -triple=riscv64 \
-# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS %s
+# RUN:     | FileCheck -check-prefixes=CHECK-EXPAND,CHECK-ALIAS,CHECK-ASM %s
 # RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
 # RUN:     | llvm-objdump -M no-aliases -d - \
 # RUN:     | FileCheck -check-prefixes=CHECK-OBJ-NOALIAS,CHECK-EXPAND,CHECK-INST %s
@@ -20,6 +20,10 @@
 # Needed for testing valid %pcrel_lo expressions
 .Lpcrel_hi0: auipc a0, %pcrel_hi(foo)
 
+# Needed for testing li with a symbol difference
+.Lbuf: .skip 8
+.Lbuf_end:
+
 # CHECK-INST: addi a0, zero, 0
 # CHECK-ALIAS: li a0, 0
 li x10, 0
@@ -215,6 +219,12 @@
 # CHECK-EXPAND: addiw a0, a0, 801
 li a0, CONST
 
+.equ CONST, .Lbuf_end - .Lbuf
+# CHECK-ASM: li a0, CONST
+# CHECK-ASM-NOALIAS: addi a0, zero, CONST
+# CHECK-OBJ-NOALIAS: addi a0, zero, 8
+li a0, CONST
+
 # CHECK-INST: subw t6, zero, ra
 # CHECK-ALIAS: negw t6, ra
 negw x31, x1