Index: llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -1297,7 +1297,8 @@
   parseNamedBit(const char *Name, OperandVector &Operands,
                 AMDGPUOperand::ImmTy ImmTy = AMDGPUOperand::ImmTyNone);
   OperandMatchResultTy parseStringWithPrefix(StringRef Prefix,
-                                             StringRef &Value);
+                                             StringRef &Value,
+                                             SMLoc &StringLoc);
 
   bool isModifier();
   bool isOperandModifier(const AsmToken &Token, const AsmToken &NextToken) const;
@@ -5099,11 +5100,15 @@
 }
 
 OperandMatchResultTy
-AMDGPUAsmParser::parseStringWithPrefix(StringRef Prefix, StringRef &Value) {
+AMDGPUAsmParser::parseStringWithPrefix(StringRef Prefix,
+                                       StringRef &Value,
+                                       SMLoc &StringLoc) {
   if (!trySkipId(Prefix, AsmToken::Colon))
     return MatchOperand_NoMatch;
 
-  return parseId(Value) ? MatchOperand_Success : MatchOperand_ParseFail;
+  StringLoc = getLoc();
+  return parseId(Value, "expected an identifier") ? MatchOperand_Success
+                                                  : MatchOperand_ParseFail;
 }
 
 //===----------------------------------------------------------------------===//
@@ -7523,7 +7528,8 @@
   StringRef Value;
   OperandMatchResultTy res;
 
-  res = parseStringWithPrefix(Prefix, Value);
+  SMLoc StringLoc;
+  res = parseStringWithPrefix(Prefix, Value, StringLoc);
   if (res != MatchOperand_Success) {
     return res;
   }
@@ -7540,6 +7546,7 @@
         .Default(0xffffffff);
 
   if (Int == 0xffffffff) {
+    Error(StringLoc, "invalid " + Twine(Prefix) + " value");
     return MatchOperand_ParseFail;
   }
 
@@ -7555,7 +7562,8 @@
   StringRef Value;
   OperandMatchResultTy res;
 
-  res = parseStringWithPrefix("dst_unused", Value);
+  SMLoc StringLoc;
+  res = parseStringWithPrefix("dst_unused", Value, StringLoc);
   if (res != MatchOperand_Success) {
     return res;
   }
@@ -7568,6 +7576,7 @@
         .Default(0xffffffff);
 
   if (Int == 0xffffffff) {
+    Error(StringLoc, "invalid dst_unused value");
     return MatchOperand_ParseFail;
   }
 
Index: llvm/test/MC/AMDGPU/gfx10_err_pos.s
===================================================================
--- llvm/test/MC/AMDGPU/gfx10_err_pos.s
+++ llvm/test/MC/AMDGPU/gfx10_err_pos.s
@@ -483,6 +483,24 @@
 // CHECK-NEXT:{{^}}v_mov_b32_sdwa v1, sext(u)
 // CHECK-NEXT:{{^}}                        ^
 
+//==============================================================================
+// expected an identifier
+
+v_mov_b32_sdwa v5, v1 dst_sel:
+// CHECK: error: expected an identifier
+// CHECK-NEXT:{{^}}v_mov_b32_sdwa v5, v1 dst_sel:
+// CHECK-NEXT:{{^}}                              ^
+
+v_mov_b32_sdwa v5, v1 dst_sel:0
+// CHECK: error: expected an identifier
+// CHECK-NEXT:{{^}}v_mov_b32_sdwa v5, v1 dst_sel:0
+// CHECK-NEXT:{{^}}                              ^
+
+v_mov_b32_sdwa v5, v1 dst_sel:DWORD dst_unused:[UNUSED_PAD]
+// CHECK: error: expected an identifier
+// CHECK-NEXT:{{^}}v_mov_b32_sdwa v5, v1 dst_sel:DWORD dst_unused:[UNUSED_PAD]
+// CHECK-NEXT:{{^}}                                               ^
+
 //==============================================================================
 // expected an opening square bracket
 
@@ -623,6 +641,22 @@
 // CHECK-NEXT:{{^}}s_waitcnt vmcnt(0) & expcnt(0) x(0)
 // CHECK-NEXT:{{^}}                               ^
 
+//==============================================================================
+// invalid dst_sel value
+
+v_mov_b32_sdwa v5, v1 dst_sel:WORD
+// CHECK: error: invalid dst_sel value
+// CHECK-NEXT:{{^}}v_mov_b32_sdwa v5, v1 dst_sel:WORD
+// CHECK-NEXT:{{^}}                              ^
+
+//==============================================================================
+// invalid dst_unused value
+
+v_mov_b32_sdwa v5, v1 dst_unused:UNUSED
+// CHECK: error: invalid dst_unused value
+// CHECK-NEXT:{{^}}v_mov_b32_sdwa v5, v1 dst_unused:UNUSED
+// CHECK-NEXT:{{^}}                                 ^
+
 //==============================================================================
 // invalid exp target