Issue #7117 (backport py3k float repr) continued:

 - add double endianness detection to configure script
 - add configure-time check to see whether we can use inline
   assembly to get and set x87 control word in configure script
 - add functions to get and set x87 control word in Python/pymath.c
 - add pyport.h logic to determine whether it's safe to use the
   short float repr or not

1 files changed, 299 insertions, 6 deletions

diff --git a/configure b/configure
index 82f60bec2f..e774d5e4bb 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 74978 .
+# From configure.in Revision: 75131 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.61 for python 2.7.
 #
@@ -23233,12 +23233,298 @@ echo "${ECHO_T}default LIBC=\"$LIBC\"" >&6; }
 fi
 
 
-# ************************************
-# * Check for mathematical functions *
-# ************************************
+# **************************************************
+# * Check for various properties of floating point *
+# **************************************************
 
-LIBS_SAVE=$LIBS
-LIBS="$LIBS $LIBM"
+{ echo "$as_me:$LINENO: checking whether C doubles are little-endian IEEE 754 binary64" >&5
+echo $ECHO_N "checking whether C doubles are little-endian IEEE 754 binary64... $ECHO_C" >&6; }
+if test "${ac_cv_little_endian_double+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+
+if test "$cross_compiling" = yes; then
+  ac_cv_little_endian_double=no
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+#include <string.h>
+int main() {
+    double x = 9006104071832581.0;
+    if (memcmp(&x, "\x05\x04\x03\x02\x01\xff\x3f\x43", 8) == 0)
+        return 0;
+    else
+        return 1;
+}
+
+_ACEOF
+rm -f conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_link") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_little_endian_double=yes
+else
+  echo "$as_me: program exited with status $ac_status" >&5
+echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+( exit $ac_status )
+ac_cv_little_endian_double=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
+fi
+
+
+fi
+
+{ echo "$as_me:$LINENO: result: $ac_cv_little_endian_double" >&5
+echo "${ECHO_T}$ac_cv_little_endian_double" >&6; }
+if test "$ac_cv_little_endian_double" = yes
+then
+
+cat >>confdefs.h <<\_ACEOF
+#define DOUBLE_IS_LITTLE_ENDIAN_IEEE754 1
+_ACEOF
+
+fi
+
+{ echo "$as_me:$LINENO: checking whether C doubles are big-endian IEEE 754 binary64" >&5
+echo $ECHO_N "checking whether C doubles are big-endian IEEE 754 binary64... $ECHO_C" >&6; }
+if test "${ac_cv_big_endian_double+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+
+if test "$cross_compiling" = yes; then
+  ac_cv_big_endian_double=no
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+#include <string.h>
+int main() {
+    double x = 9006104071832581.0;
+    if (memcmp(&x, "\x43\x3f\xff\x01\x02\x03\x04\x05", 8) == 0)
+        return 0;
+    else
+        return 1;
+}
+
+_ACEOF
+rm -f conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_link") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_big_endian_double=yes
+else
+  echo "$as_me: program exited with status $ac_status" >&5
+echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+( exit $ac_status )
+ac_cv_big_endian_double=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
+fi
+
+
+fi
+
+{ echo "$as_me:$LINENO: result: $ac_cv_big_endian_double" >&5
+echo "${ECHO_T}$ac_cv_big_endian_double" >&6; }
+if test "$ac_cv_big_endian_double" = yes
+then
+
+cat >>confdefs.h <<\_ACEOF
+#define DOUBLE_IS_BIG_ENDIAN_IEEE754 1
+_ACEOF
+
+fi
+
+# Some ARM platforms use a mixed-endian representation for doubles.
+# While Python doesn't currently have full support for these platforms
+# (see e.g., issue 1762561), we can at least make sure that float <-> string
+# conversions work.
+{ echo "$as_me:$LINENO: checking whether C doubles are ARM mixed-endian IEEE 754 binary64" >&5
+echo $ECHO_N "checking whether C doubles are ARM mixed-endian IEEE 754 binary64... $ECHO_C" >&6; }
+if test "${ac_cv_mixed_endian_double+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+
+if test "$cross_compiling" = yes; then
+  ac_cv_mixed_endian_double=no
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+#include <string.h>
+int main() {
+    double x = 9006104071832581.0;
+    if (memcmp(&x, "\x01\xff\x3f\x43\x05\x04\x03\x02", 8) == 0)
+        return 0;
+    else
+        return 1;
+}
+
+_ACEOF
+rm -f conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_link") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && { ac_try='./conftest$ac_exeext'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_mixed_endian_double=yes
+else
+  echo "$as_me: program exited with status $ac_status" >&5
+echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+( exit $ac_status )
+ac_cv_mixed_endian_double=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
+fi
+
+
+fi
+
+{ echo "$as_me:$LINENO: result: $ac_cv_mixed_endian_double" >&5
+echo "${ECHO_T}$ac_cv_mixed_endian_double" >&6; }
+if test "$ac_cv_mixed_endian_double" = yes
+then
+
+cat >>confdefs.h <<\_ACEOF
+#define DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754 1
+_ACEOF
+
+fi
+
+# The short float repr introduced in Python 3.1 requires the
+# correctly-rounded string <-> double conversion functions from
+# Python/dtoa.c, which in turn require that the FPU uses 53-bit
+# rounding; this is a problem on x86, where the x87 FPU has a default
+# rounding precision of 64 bits.  For gcc/x86, we try to fix this by
+# using inline assembler to get and set the x87 FPU control word.
+if test "$GCC" = yes && test -n "`$CC -dM -E - </dev/null | grep i386`"
+then
+    # Check that it's okay to use gcc inline assembler to get and set
+    # x87 control word.  It should be, but you never know...
+    { echo "$as_me:$LINENO: checking whether we can use gcc inline assembler to get and set x87 control word" >&5
+echo $ECHO_N "checking whether we can use gcc inline assembler to get and set x87 control word... $ECHO_C" >&6; }
+    cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+      unsigned short cw;
+      __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
+      __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
+
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext
+if { (ac_try="$ac_compile"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_compile") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && {
+	 test -z "$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest.$ac_objext; then
+  have_gcc_asm_for_x87=yes
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	have_gcc_asm_for_x87=no
+fi
+
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+    { echo "$as_me:$LINENO: result: $have_gcc_asm_for_x87" >&5
+echo "${ECHO_T}$have_gcc_asm_for_x87" >&6; }
+    if test "$have_gcc_asm_for_x87" = yes
+    then
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_GCC_ASM_FOR_X87 1
+_ACEOF
+
+    fi
+fi
 
 # Detect whether system arithmetic is subject to x87-style double
 # rounding issues.  The result of this test has little meaning on non
@@ -23327,6 +23613,13 @@ _ACEOF
 
 fi
 
+# ************************************
+# * Check for mathematical functions *
+# ************************************
+
+LIBS_SAVE=$LIBS
+LIBS="$LIBS $LIBM"
+
 # Multiprocessing check for broken sem_getvalue
 { echo "$as_me:$LINENO: checking for broken sem_getvalue" >&5
 echo $ECHO_N "checking for broken sem_getvalue... $ECHO_C" >&6; }