Fix PR1836: in the interpreter, read and write apints

using the minimum possible number of bytes.  For little
endian targets run on little endian machines, apints are
stored in memory from LSB to MSB as before.  For big endian
targets on big endian machines they are stored from MSB to
LSB which wasn't always the case before (if the target and
host endianness doesn't match values are stored according
to the host's endianness).  Doing this requires knowing the
endianness of the host, which is determined when configuring -
thanks go to Anton for this.  Only having access to little
endian machines I was unable to properly test the big endian
part, which is also the most complicated...


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44796 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetData.h

@@ -23,6 +23,7 @@
 #include "llvm/Pass.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/Config/config.h"
 #include <string>
 
 namespace llvm {
@@ -142,6 +143,16 @@ public:
   bool          isLittleEndian()       const { return     LittleEndian; }
   bool          isBigEndian()          const { return    !LittleEndian; }
 
+  /// Host endianness...
+  bool hostIsLittleEndian() const {
+#ifdef LSB_FIRST
+    return true;
+#else
+    return false;
+#endif
+  }
+  bool hostIsBigEndian() const { return !hostIsLittleEndian(); }
+
   /// getStringRepresentation - Return the string representation of the
   /// TargetData.  This representation is in the same format accepted by the
   /// string constructor above.