Index: llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
===================================================================
--- llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -1655,6 +1655,8 @@
   const AsmToken &Tok = Parser.getTok();
   // Eat "{" and mark the current place.
   const SMLoc consumedToken = consumeToken();
+  if (Tok.isNot(AsmToken::Identifier))
+    return ErrorOperand(Tok.getLoc(), "Expected an identifier after {");
   if (Tok.getIdentifier().startswith("r")){
     int rndMode = StringSwitch<int>(Tok.getIdentifier())
       .Case("rn", X86::STATIC_ROUNDING::TO_NEAREST_INT)
Index: llvm/test/MC/X86/avx512-err.s
===================================================================
--- llvm/test/MC/X86/avx512-err.s
+++ llvm/test/MC/X86/avx512-err.s
@@ -11,3 +11,6 @@
 
 // ERR: invalid operand for instruction
 cvtsd2sil  {rn-sae}, %xmm1, %eax
+
+// ERR: Expected an identifier after {
+cvtsd2sil  {{sae}, %xmm1, %eax