Index: llvm/include/llvm/CodeGen/TargetInstrInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -1505,6 +1505,9 @@
     const char *Str, const MCAsmInfo &MAI,
     const TargetSubtargetInfo *STI = nullptr) const;
 
+  /// Return the target inline asm constraint name
+  virtual StringRef getInlineAsmMemConstraintName(unsigned Constraint) const;
+
   /// Allocate and return a hazard recognizer to use for this target when
   /// scheduling the machine instructions before register allocation.
   virtual ScheduleHazardRecognizer *
Index: llvm/include/llvm/IR/InlineAsm.h
===================================================================
--- llvm/include/llvm/IR/InlineAsm.h
+++ llvm/include/llvm/IR/InlineAsm.h
@@ -315,7 +315,6 @@
   static unsigned getFlagWordForMem(unsigned InputFlag, unsigned Constraint) {
     assert(isMemKind(InputFlag) && "InputFlag is not a memory constraint!");
     assert(Constraint <= 0x7fff && "Too large a memory constraint ID");
-    assert(Constraint <= Constraints_Max && "Unknown constraint ID");
     assert((InputFlag & ~0xffff) == 0 && "High bits already contain data");
     return InputFlag | (Constraint << Constraints_ShiftAmount);
   }
Index: llvm/lib/CodeGen/MachineInstr.cpp
===================================================================
--- llvm/lib/CodeGen/MachineInstr.cpp
+++ llvm/lib/CodeGen/MachineInstr.cpp
@@ -1757,7 +1757,10 @@
 
       if (InlineAsm::isMemKind(Flag)) {
         unsigned MCID = InlineAsm::getMemoryConstraintID(Flag);
-        OS << ":" << InlineAsm::getMemConstraintName(MCID);
+        if (TII)
+          OS << ":" << TII -> getInlineAsmMemConstraintName(MCID);
+        else
+          OS << ":CONSTRAINT" << MCID;
       }
 
       unsigned TiedTo = 0;
Index: llvm/lib/CodeGen/TargetInstrInfo.cpp
===================================================================
--- llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -135,6 +135,12 @@
   return Length;
 }
 
+/// Return the target constraint name
+StringRef
+TargetInstrInfo::getInlineAsmMemConstraintName(unsigned Constraint) const {
+  return InlineAsm::getMemConstraintName(Constraint);
+}
+
 /// ReplaceTailWithBranchTo - Delete the instruction OldInst and everything
 /// after it, replacing it with an unconditional branch to NewDest.
 void
@@ -1389,7 +1395,7 @@
 
   if (InlineAsm::isMemKind(Flag)) {
     unsigned MCID = InlineAsm::getMemoryConstraintID(Flag);
-    OS << ":" << InlineAsm::getMemConstraintName(MCID);
+    OS << ":" << getInlineAsmMemConstraintName(MCID);
   }
 
   unsigned TiedTo = 0;