Index: lib/AsmParser/LLLexer.cpp
===================================================================
--- lib/AsmParser/LLLexer.cpp
+++ lib/AsmParser/LLLexer.cpp
@@ -105,7 +105,7 @@
     Pair[1] += hexDigitValue(*Buffer);
   }
   Pair[0] = 0;
-  for (int i=0; i<16; i++, Buffer++) {
+  for (int i = 0; i < 16 && Buffer != End; i++, Buffer++) {
     Pair[0] *= 16;
     Pair[0] += hexDigitValue(*Buffer);
   }
Index: test/Assembler/invalid-fp80hex.ll
===================================================================
--- /dev/null
+++ test/Assembler/invalid-fp80hex.ll
@@ -0,0 +1,6 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+; Tests bug: 24640
+; CHECK: expected '=' in global variable
+
+@- 0xKate potb8ed