Index: include/llvm/IR/InlineAsm.h
===================================================================
--- include/llvm/IR/InlineAsm.h
+++ include/llvm/IR/InlineAsm.h
@@ -244,6 +244,7 @@
     Constraint_m,
     Constraint_o,
     Constraint_v,
+    Constraint_A,
     Constraint_Q,
     Constraint_R,
     Constraint_S,
Index: lib/Target/RISCV/RISCVAsmPrinter.cpp
===================================================================
--- lib/Target/RISCV/RISCVAsmPrinter.cpp
+++ lib/Target/RISCV/RISCVAsmPrinter.cpp
@@ -115,7 +115,7 @@
     if (!MO.isReg())
       return true;
 
-    OS << "0(" << RISCVInstPrinter::getRegisterName(MO.getReg()) << ")";
+    OS << "(" << RISCVInstPrinter::getRegisterName(MO.getReg()) << ")";
     return false;
   }
 
Index: lib/Target/RISCV/RISCVISelDAGToDAG.cpp
===================================================================
--- lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -172,6 +172,9 @@
     // operand and need no special handling.
     OutOps.push_back(Op);
     return false;
+  case InlineAsm::Constraint_A:
+    OutOps.push_back(Op);
+    return false;
   default:
     break;
   }
Index: lib/Target/RISCV/RISCVISelLowering.h
===================================================================
--- lib/Target/RISCV/RISCVISelLowering.h
+++ lib/Target/RISCV/RISCVISelLowering.h
@@ -89,6 +89,11 @@
   // This method returns the name of a target specific DAG node.
   const char *getTargetNodeName(unsigned Opcode) const override;
 
+  // Get the type of an inline asm constraint.
+  ConstraintType getConstraintType(StringRef Constraint) const override;
+
+  unsigned getInlineAsmMemConstraint(StringRef ConstraintCode) const override;
+
   std::pair<unsigned, const TargetRegisterClass *>
   getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                StringRef Constraint, MVT VT) const override;
Index: lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- lib/Target/RISCV/RISCVISelLowering.cpp
+++ lib/Target/RISCV/RISCVISelLowering.cpp
@@ -2141,6 +2141,21 @@
   return nullptr;
 }
 
+RISCVTargetLowering::ConstraintType
+RISCVTargetLowering::getConstraintType(StringRef Constraint) const {
+  // Currently only support length 1 constraints.
+  if (Constraint.size() == 1) {
+    switch (Constraint[0]) {
+    case 'A':
+      return C_Memory;
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getConstraintType(Constraint);
+}
+
 std::pair<unsigned, const TargetRegisterClass *>
 RISCVTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                                   StringRef Constraint,
@@ -2159,6 +2174,21 @@
   return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
 }
 
+unsigned
+RISCVTargetLowering::getInlineAsmMemConstraint(StringRef ConstraintCode) const {
+  // Currently only support length 1 constraints.
+  if (ConstraintCode.size() == 1) {
+    switch (ConstraintCode[0]) {
+    case 'A':
+      return InlineAsm::Constraint_A;
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getInlineAsmMemConstraint(ConstraintCode);
+}
+
 void RISCVTargetLowering::LowerAsmOperandForConstraint(
     SDValue Op, std::string &Constraint, std::vector<SDValue> &Ops,
     SelectionDAG &DAG) const {
Index: test/CodeGen/RISCV/inline-asm.ll
===================================================================
--- test/CodeGen/RISCV/inline-asm.ll
+++ test/CodeGen/RISCV/inline-asm.ll
@@ -68,14 +68,14 @@
 ; RV32I-LABEL: constraint_m2:
 ; RV32I:       # %bb.0:
 ; RV32I-NEXT:    #APP
-; RV32I-NEXT:    lw a0, 0(a0)
+; RV32I-NEXT:    lw a0, (a0)
 ; RV32I-NEXT:    #NO_APP
 ; RV32I-NEXT:    ret
 ;
 ; RV64I-LABEL: constraint_m2:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    #APP
-; RV64I-NEXT:    lw a0, 0(a0)
+; RV64I-NEXT:    lw a0, (a0)
 ; RV64I-NEXT:    #NO_APP
 ; RV64I-NEXT:    ret
   %1 = tail call i32 asm "lw $0, $1", "=r,*m"(i32* %a) nounwind
@@ -150,4 +150,29 @@
   ret void
 }
 
+define void @constraint_A(i8* %a) nounwind {
+; RV32I-LABEL: constraint_A:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    sb s0, (a0)
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    lb s1, (a0)
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: constraint_A:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    #APP
+; RV64I-NEXT:    sb s0, (a0)
+; RV64I-NEXT:    #NO_APP
+; RV64I-NEXT:    #APP
+; RV64I-NEXT:    lb s1, (a0)
+; RV64I-NEXT:    #NO_APP
+; RV64I-NEXT:    ret
+  tail call void asm sideeffect "sb s0, $0", "*A"(i8* %a)
+  tail call void asm sideeffect "lb s1, $0", "*A"(i8* %a)
+  ret void
+}
+
 ; TODO: expend tests for more complex constraints, out of range immediates etc