Don't assume underlying APInt type is limited
to 64 bits.

llvm-svn: 51135
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index de33382..0ee3d54 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -2003,7 +2003,7 @@
   firstSignificantDigit = p;
 
   for(;;) {
-    uint64_t hex_value;
+    integerPart hex_value;
 
     if(*p == '.') {
       assert(dot == 0);