[gcc(refs/users/marxin/heads/PR94249-lto-plugin-v3)] Improve endianess detection.

[Martin Liska <marxin@gcc.gnu.org>]

https://gcc.gnu.org/g:d7699407e3133651e6b8753ccd4dab71915dd6a9

commit d7699407e3133651e6b8753ccd4dab71915dd6a9
Author: Martin Liska <mliska@suse.cz>
Date:   Tue Mar 24 09:12:50 2020 +0100

    Improve endianess detection.
    
    include/ChangeLog:
    
    2020-03-24  Martin Liska  <mliska@suse.cz>
    
            PR lto/94249
            * plugin-api.h: Add more robust endianess detection.

Diff:
---
 include/plugin-api.h | 44 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/include/plugin-api.h b/include/plugin-api.h
index 673f136ce68..a530cb08e2b 100644
--- a/include/plugin-api.h
+++ b/include/plugin-api.h
@@ -42,6 +42,44 @@ extern "C"
 {
 #endif
 
+/* Detect endianess based on __BYTE_ORDER__ macro.  */
+#if defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && defined(__ORDER_LITTLE_ENDIAN__)
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define PLUGIN_LITTLE_ENDIAN 1
+#endif
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define PLUGIN_BIG_ENDIAN 1
+#endif
+#else
+/* Include all necessary header files based on target.  */
+#if defined(__SVR4) && defined(__sun)
+#include <sys/byteorder.h>
+#endif
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__DragonFly__) || defined(__minix)
+#include <sys/endian.h>
+#endif
+#if defined(__OpenBSD__)
+#include <machine/endian.h>
+#endif
+/* Detect endianess based on _BYTE_ORDER.  */
+#if _BYTE_ORDER == _LITTLE_ENDIAN
+#define PLUGIN_LITTLE_ENDIAN 1
+#elif _BYTE_ORDER == _BIG_ENDIAN
+#define PLUGIN_BIG_ENDIAN 1
+#endif
+/* Detect based on _WIN32.  */
+#if defined(_WIN32)
+#define PLUGIN_LITTLE_ENDIAN 1
+#endif
+/* Fallback to __BIG_ENDIAN__ and __LITTLE_ENDIAN__ */
+#ifdef __LITTLE_ENDIAN__
+#define PLUGIN_LITTLE_ENDIAN 1
+#endif
+#ifdef __BIG_ENDIAN__
+#define PLUGIN_BIG_ENDIAN 1
+#endif
+#endif
+
 /* Status code returned by most API routines.  */
 
 enum ld_plugin_status
@@ -89,16 +127,18 @@ struct ld_plugin_symbol
   char *version;
   /* This is for compatibility with older ABIs.  The older ABI defined
      only 'def' field.  */
-#ifdef __BIG_ENDIAN__
+#if PLUGIN_BIG_ENDIAN == 1
   char unused;
   char section_kind;
   char symbol_type;
   char def;
-#else
+#elif PLUGIN_LITTLE_ENDIAN == 1
   char def;
   char symbol_type;
   char section_kind;
   char unused;
+#else
+#error "Could not detect architecture endianess"
 #endif
   int visibility;
   uint64_t size;