Index: lib/Target/RISCV/RISCVAsmPrinter.cpp
===================================================================
--- lib/Target/RISCV/RISCVAsmPrinter.cpp
+++ lib/Target/RISCV/RISCVAsmPrinter.cpp
@@ -92,20 +92,37 @@
   if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
     return false;
 
-  if (!ExtraCode) {
-    const MachineOperand &MO = MI->getOperand(OpNo);
-    switch (MO.getType()) {
-    case MachineOperand::MO_Immediate:
-      OS << MO.getImm();
-      return false;
-    case MachineOperand::MO_Register:
-      OS << RISCVInstPrinter::getRegisterName(MO.getReg());
-      return false;
+  const MachineOperand &MO = MI->getOperand(OpNo);
+  if (ExtraCode && ExtraCode[0]) {
+    if (ExtraCode[1] != 0) return true; // Unknown modifier.
+
+    switch (ExtraCode[0]) {
     default:
+      return true; // Unknown modifier
+    case 'z': // Print zero register if zero, regular printing otherwise
+      if (MO.isImm() && MO.getImm() == 0) {
+        OS << RISCVInstPrinter::getRegisterName(RISCV::X0);
+        return false;
+      }
       break;
+    case 'i': // Literal 'i' if operand is not a register
+      if (!MO.isReg())
+        OS << 'i';
+      return false;
     }
   }
 
+  switch (MO.getType()) {
+  case MachineOperand::MO_Immediate:
+    OS << MO.getImm();
+    return false;
+  case MachineOperand::MO_Register:
+    OS << RISCVInstPrinter::getRegisterName(MO.getReg());
+    return false;
+  default:
+    break;
+  }
+
   return true;
 }
 
Index: test/CodeGen/RISCV/inline-asm.ll
===================================================================
--- test/CodeGen/RISCV/inline-asm.ll
+++ test/CodeGen/RISCV/inline-asm.ll
@@ -107,4 +107,49 @@
   ret void
 }
 
+define i32 @modifier_z_zero(i32 %a) {
+; RV32I-LABEL: modifier_z_zero:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    add a0, a0, zero
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+  %1 = tail call i32 asm "add $0, $1, ${2:z}", "=r,r,r"(i32 %a, i32 0)
+  ret i32 %1
+}
+
+define i32 @modifier_z_nonzero(i32 %a) {
+; RV32I-LABEL: modifier_z_nonzero:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    addi a1, zero, 1
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    add a0, a0, a1
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+  %1 = tail call i32 asm "add $0, $1, ${2:z}", "=r,r,r"(i32 %a, i32 1)
+  ret i32 %1
+}
+
+define i32 @modifier_i_imm(i32 %a) {
+; RV32I-LABEL: modifier_i_imm:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    addi a0, a0, 1
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+  %1 = tail call i32 asm "add${2:i} $0, $1, $2", "=r,r,ri"(i32 %a, i32 1)
+  ret i32 %1
+}
+
+define i32 @modifier_i_reg(i32 %a, i32 %b) {
+; RV32I-LABEL: modifier_i_reg:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    add a0, a0, a1
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+  %1 = tail call i32 asm "add${2:i} $0, $1, $2", "=r,r,ri"(i32 %a, i32 %b)
+  ret i32 %1
+}
+
 ; TODO: expend tests for more complex constraints, out of range immediates etc