Cope with big endian float word order on little endian machines

1 files changed, 27 insertions, 0 deletions

diff --git a/aclocal.m4 b/aclocal.m4
index 619d414fb9..9d1e1cab9b 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -4,6 +4,33 @@
 # ensure we don't clash with any pre-supplied autoconf ones.
 
 
+# FPTOOLS_FLOAT_WORD_ORDER_BIGENDIAN
+# ----------------------------------
+# Little endian Arm on Linux with some ABIs has big endian word order
+# in doubles. Define FLOAT_WORDS_BIGENDIAN if this is the case.
+AC_DEFUN([FPTOOLS_FLOAT_WORD_ORDER_BIGENDIAN],
+  [AC_CACHE_CHECK([whether float word order is big endian], [fptools_cv_float_word_order_bigendian],
+    [AC_COMPILE_IFELSE(
+      [AC_LANG_PROGRAM(
+        [#include <endian.h>],
+        [#if defined(__FLOAT_WORD_ORDER) && __FLOAT_WORD_ORDER == BIG_ENDIAN
+             return 0;
+         #else
+             not float word order big endian
+         #endif]
+      )],
+      [fptools_cv_float_word_order_bigendian=yes],
+      [fptools_cv_float_word_order_bigendian=no])
+    ])
+  case $fptools_cv_float_word_order_bigendian in
+      yes)
+          AC_DEFINE([FLOAT_WORDS_BIGENDIAN], 1,
+          [Define to 1 if your processor stores words of floats with
+           the most significant byte first]) ;;
+  esac
+])
+
+
 # FP_EVAL_STDERR(COMMAND)
 # -----------------------
 # Eval COMMAND, save its stderr (without lines resulting from shell tracing)