Index: llvm/lib/MC/MCParser/AsmParser.cpp
===================================================================
--- llvm/lib/MC/MCParser/AsmParser.cpp
+++ llvm/lib/MC/MCParser/AsmParser.cpp
@@ -3076,6 +3076,12 @@
   // Convert to an APFloat.
   APFloat Value(Semantics);
   StringRef IDVal = getTok().getString();
+
+  // We do not currently handle ASCII literals e.g. 't' = 116
+  if(getLexer().is(AsmToken::Integer) && IDVal.startswith("'")){
+    return TokError("ASCII literal not supported");
+  }
+
   if (getLexer().is(AsmToken::Identifier)) {
     if (!IDVal.compare_lower("infinity") || !IDVal.compare_lower("inf"))
       Value = APFloat::getInf(Semantics);
Index: llvm/test/MC/AsmParser/floating-literals.s
===================================================================
--- llvm/test/MC/AsmParser/floating-literals.s
+++ llvm/test/MC/AsmParser/floating-literals.s
@@ -90,6 +90,8 @@
 .double 1e1e
 # CHECK-ERROR: Invalid sign in float literal
 .double 2.+1
+#CHECK-ERROR: error: ASCII literal not supported in '.double' directive
+.double 't'
 
 # CHECK: .long 1310177520
 .float 0x12f7.1ep+17