Issue #1580: use short float repr where possible.
- incorporate and adapt David Gay's dtoa and strtod
into the Python core
- on platforms where we can use Gay's code (almost
all!), repr(float) is based on the shortest
sequence of decimal digits that rounds correctly.
- add sys.float_repr_style attribute to indicate
whether we're using Gay's code or not
- add autoconf magic to detect and enable SSE2
instructions on x86/gcc
- slight change to repr and str: repr switches
to exponential notation at 1e16 instead of
1e17, str switches at 1e11 instead of 1e12
diff --git a/configure b/configure
index f5d7352..f4ee310 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
#! /bin/sh
-# From configure.in Revision: 71261 .
+# From configure.in Revision: 71274 .
# Guess values for system-dependent variables and create Makefiles.
# Generated by GNU Autoconf 2.61 for python 3.1.
#
@@ -21603,12 +21603,455 @@
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
+
+# David Gay's code in Python/dtoa.c requires that the FPU uses 53-bit
+# rounding; this is a particular problem on x86, where the x87 FPU has
+# a default rounding precision of 64 bits. For gcc/x86, we try to fix
+# this by:
+#
+# (1) using the SSE2 instruction set when available (it usually is
+# on modern machines)
+# (2) using inline assembler to get and set the x87 FPU control word
+# otherwise.
+#
+# On AMD64 (aka x86-64), gcc automatically enables use of SSE2
+# instructions, so we don't bother trying to detect.
+
+if test "$GCC" = yes && test -n "`$CC -dM -E - </dev/null | grep i386`"
+then
+ # determine whether we're already using the SSE2 instruction set for math
+ # (e.g., this is true by default on OS X/x86)
+ { echo "$as_me:$LINENO: checking whether SSE2 instructions are already enabled for math" >&5
+echo $ECHO_N "checking whether SSE2 instructions are already enabled for math... $ECHO_C" >&6; }
+ if test -n "`$CC -dM -E - </dev/null | grep __SSE2_MATH__`"
+ then
+ ac_sse2_enabled=yes
+ else
+ ac_sse2_enabled=no
+ fi
+ { echo "$as_me:$LINENO: result: $ac_sse2_enabled" >&5
+echo "${ECHO_T}$ac_sse2_enabled" >&6; }
+
+ # if we're not using SSE2 already, we need to either enable it
+ # (when available), or use inline assembler to get and set the
+ # 387 control word.
+ if test $ac_sse2_enabled = no
+ then
+ # Check cpuid for SSE2 availability. Bits 25 and 26 of edx tell
+ # us about SSE and SSE2 respectively.
+ { echo "$as_me:$LINENO: checking whether SSE2 instructions are available on this CPU" >&5
+echo $ECHO_N "checking whether SSE2 instructions are available on this CPU... $ECHO_C" >&6; }
+ if test "$cross_compiling" = yes; then
+ ac_cv_cpu_has_sse2=no
+else
+ cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h. */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h. */
+
+ int main() {
+ unsigned int ax, bx, cx, dx, func;
+ func = 1U;
+ __asm__ __volatile__ (
+ "pushl %%ebx\n\t" /* don't clobber ebx */
+ "cpuid\n\t"
+ "movl %%ebx, %1\n\t"
+ "popl %%ebx"
+ : "=a" (ax), "=r" (bx), "=c" (cx), "=d" (dx)
+ : "a" (func)
+ : "cc" );
+ if ((dx & (1U << 25)) && (dx & (1U << 26)))
+ return 0;
+ else
+ return 1;
+ }
+
+_ACEOF
+rm -f conftest$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 $ac_status); }; }; then
+ ac_cv_cpu_has_sse2=yes
+else
+ echo "$as_me: program exited with status $ac_status" >&5
+echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+( exit $ac_status )
+ac_cv_cpu_has_sse2=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
+fi
+
+
+ { echo "$as_me:$LINENO: result: $ac_cv_cpu_has_sse2" >&5
+echo "${ECHO_T}$ac_cv_cpu_has_sse2" >&6; }
+
+ # determine whether gcc accepts options to turn on SSE2
+ { echo "$as_me:$LINENO: checking whether $CC accepts -msse2 -mfpmath=sse" >&5
+echo $ECHO_N "checking whether $CC accepts -msse2 -mfpmath=sse... $ECHO_C" >&6; }
+ ac_save_cc="$CC"
+ CC="$CC -msse2 -mfpmath=sse"
+ if test "$cross_compiling" = yes; then
+ ac_cv_msse2_ok=no
+else
+ cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h. */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h. */
+int main() { return 0; }
+_ACEOF
+rm -f conftest$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 $ac_status); }; }; then
+ ac_cv_msse2_ok=yes
+else
+ echo "$as_me: program exited with status $ac_status" >&5
+echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+( exit $ac_status )
+ac_cv_msse2_ok=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext
+fi
+
+
+ CC="$ac_save_cc"
+ { echo "$as_me:$LINENO: result: $ac_cv_msse2_ok" >&5
+echo "${ECHO_T}$ac_cv_msse2_ok" >&6; }
+
+ if test $ac_cv_cpu_has_sse2 = yes && test $ac_cv_msse2_ok = yes
+ then
+ BASECFLAGS="$BASECFLAGS -msse2 -mfpmath=sse"
+ else
+ # SSE2 doesn't appear to be available. Check that it's okay
+ # to use gcc inline assembler to get and set x87 control word
+
+cat >>confdefs.h <<\_ACEOF
+#define USING_X87_FPU 1
+_ACEOF
+
+ { 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
+ fi
+fi
# Detect whether system arithmetic is subject to x87-style double
# rounding issues. The result of this test has little meaning on non
@@ -21617,10 +22060,9 @@
# 0 otherwise. See http://bugs.python.org/issue2937 for more info.
{ echo "$as_me:$LINENO: checking for x87-style double rounding" >&5
echo $ECHO_N "checking for x87-style double rounding... $ECHO_C" >&6; }
-if test "${ac_cv_x87_double_rounding+set}" = set; then
- echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-
+# $BASECFLAGS may affect the result
+ac_save_cc="$CC"
+CC="$CC $BASECFLAGS"
if test "$cross_compiling" = yes; then
ac_cv_x87_double_rounding=no
else
@@ -21684,8 +22126,7 @@
fi
-fi
-
+CC="$ac_save_cc"
{ echo "$as_me:$LINENO: result: $ac_cv_x87_double_rounding" >&5
echo "${ECHO_T}$ac_cv_x87_double_rounding" >&6; }
if test "$ac_cv_x87_double_rounding" = yes
@@ -21697,6 +22138,13 @@
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; }