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

2 files changed, 17 insertions, 0 deletions

diff --git a/include/llvm/Config/config.h.in b/include/llvm/Config/config.h.in
index 32e154a695..64858f26b9 100644
--- a/include/llvm/Config/config.h.in
+++ b/include/llvm/Config/config.h.in
@@ -494,6 +494,9 @@
 /* Installation prefix directory */
 #undef LLVM_PREFIX
 
+/* Define if this target is little endian */
+#undef LSB_FIRST
+
 /* Define if the OS needs help to load dependent libraries for dlopen(). */
 #undef LTDL_DLOPEN_DEPLIBS
 
@@ -511,6 +514,9 @@
 /* Define to the system default library search path. */
 #undef LTDL_SYSSEARCHPATH
 
+/* Define if this target is big endian */
+#undef MSB_FIRST
+
 /* Define if /dev/zero should be used when mapping RWX memory, or undefine if
    its not necessary */
 #undef NEED_DEV_ZERO_FOR_MMAP
diff --git a/include/llvm/Target/TargetData.h b/include/llvm/Target/TargetData.h
index 3136a38ac0..fd52ef380a 100644
--- a/include/llvm/Target/TargetData.h
+++ b/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.