The SSE2 detection and enabling could potentially cause

problems for binary distributions of Python in situations
where the build machine has SSE2 but the target machine
does not.

Therefore, don't enable SSE2 instructions automatically on x86.

7 files changed, 47 insertions, 280 deletions

diff --git a/Include/pyport.h b/Include/pyport.h
index 9b8b1e7..c1ed4a6 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -469,7 +469,7 @@ extern "C" {
    the FPU is using 53-bit precision.  Here are macros that force this.  See
    Python/pystrtod.c for an example of their use. */
 
-#ifdef USING_X87_FPU
+#ifdef HAVE_GCC_ASM_FOR_X87
 #define _Py_SET_53BIT_PRECISION_HEADER				\
 	unsigned short old_387controlword, new_387controlword
 #define _Py_SET_53BIT_PRECISION_START					\
diff --git a/Misc/NEWS b/Misc/NEWS
index 295ebd0..e230d82 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -31,13 +31,6 @@ Core and Builtins
   value: str(1e11 + 0.5).  (This minor issue has existed in 2.x for a
   long time.)
 
-- On x86, SSE2 instructions for floating-point are automatically
-  detected and, where possible, enabled on platforms using the gcc
-  compiler.  As a consequence, some arithmetic operations may have
-  different (more accurate!) results on some platforms, and
-  cross-platform consistency of Python arithmetic should be improved.
-  This applies particularly to Linux/x86.
-
 - Issue #1580: On most platforms, use a 'short' float repr: for a
   finite float x, repr(x) now outputs a string based on the shortest
   sequence of decimal digits that rounds to x.  Previous behaviour was
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index b7b5220..f78f7df 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -15,6 +15,11 @@
 #define MAX(x, y) ((x) < (y) ? (y) : (x))
 #define MIN(x, y) ((x) < (y) ? (x) : (y))
 
+/* ascii character tests (as opposed to locale tests) */
+#define ISSPACE(c)  ((c) == ' ' || (c) == '\f' || (c) == '\n' || \
+                     (c) == '\r' || (c) == '\t' || (c) == '\v')
+#define ISDIGIT(c)  ((c) >= '0' && (c) <= '9')
+
 #ifdef HAVE_IEEEFP_H
 #include <ieeefp.h>
 #endif
@@ -188,7 +193,7 @@ PyFloat_FromString(PyObject *v)
 	}
 
 	last = s + len;
-	while (*s && isspace(Py_CHARMASK(*s)))
+	while (*s && ISSPACE(Py_CHARMASK(*s)))
 		s++;
 	if (*s == '\0') {
 		PyErr_SetString(PyExc_ValueError, "empty string for float()");
@@ -245,7 +250,7 @@ PyFloat_FromString(PyObject *v)
 	}
 	/* Since end != s, the platform made *some* kind of sense out
 	   of the input.  Trust it. */
-	while (*end && isspace(Py_CHARMASK(*end)))
+	while (*end && ISSPACE(Py_CHARMASK(*end)))
 		end++;
 	if (*end != '\0') {
 		PyOS_snprintf(buffer, sizeof(buffer),
@@ -1275,7 +1280,7 @@ float_fromhex(PyObject *cls, PyObject *arg)
 	 ********************/
 
 	/* leading whitespace and optional sign */
-	while (isspace(Py_CHARMASK(*s)))
+	while (ISSPACE(Py_CHARMASK(*s)))
 		s++;
 	if (*s == '-') {
 		s++;
@@ -1299,6 +1304,7 @@ float_fromhex(PyObject *cls, PyObject *arg)
 	s_store = s;
 	if (*s == '0') {
 		s++;
+		if (*s == 'x' || *s == 'X')
 		if (tolower(*s) == (int)'x')
 			s++;
 		else
@@ -1345,7 +1351,7 @@ float_fromhex(PyObject *cls, PyObject *arg)
 		exp = 0;
 
 	/* optional trailing whitespace leading to the end of the string */
-	while (isspace(Py_CHARMASK(*s)))
+	while (ISSPACE(Py_CHARMASK(*s)))
 		s++;
 	if (s != s_end)
 		goto parse_error;
diff --git a/Python/pymath.c b/Python/pymath.c
index a5c0dd9..db2920c 100644
--- a/Python/pymath.c
+++ b/Python/pymath.c
@@ -13,8 +13,7 @@ double _Py_force_double(double x)
 }
 #endif
 
-#ifdef USING_X87_FPU
-#  ifdef HAVE_GCC_ASM_FOR_X87
+#ifdef HAVE_GCC_ASM_FOR_X87
 
 /* inline assembly for getting and setting the 387 FPU control word on
    gcc/x86 */
@@ -29,9 +28,6 @@ void _Py_set_387controlword(unsigned short cw) {
     __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
 }
 
-#  else
-#    error "Unable to get and set x87 control word"
-#  endif
 #endif
 
 
diff --git a/configure b/configure
index de5c354..e988b85 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 71663 .
+# From configure.in Revision: 71704 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.61 for python 3.1.
 #
@@ -21827,174 +21827,21 @@ _ACEOF
 
 fi
 
-# David Gay's code in Python/dtoa.c requires that the FPU uses 53-bit
+# The short float repr introduced in Python 3.1 requires the
+# correctly-rounded string <-> double conversion functions in
+# Python/dtoa.c, which in turn require 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.
+# 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
-    # 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
+    # Check that it's okay to use gcc inline assembler to get and set
+    # x87 control word
+    { 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
+    cat >conftest.$ac_ext <<_ACEOF
 /* confdefs.h.  */
 _ACEOF
 cat confdefs.h >>conftest.$ac_ext
@@ -22005,9 +21852,9 @@ int
 main ()
 {
 
-              unsigned short cw;
-              __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
-              __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
+      unsigned short cw;
+      __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
+      __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
 
   ;
   return 0;
@@ -22039,17 +21886,15 @@ sed 's/^/| /' conftest.$ac_ext >&5
 fi
 
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-            { echo "$as_me:$LINENO: result: $have_gcc_asm_for_x87" >&5
+    { echo "$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
+    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
 
diff --git a/configure.in b/configure.in
index 7f7dc7f..618ff4e 100644
--- a/configure.in
+++ b/configure.in
@@ -3142,97 +3142,28 @@ then
    in ARM mixed-endian order (byte order 45670123)])
 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.
-
+# 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
-    # determine whether we're already using the SSE2 instruction set for math
-    # (e.g., this is true by default on OS X/x86)
-    AC_MSG_CHECKING(whether SSE2 instructions are already enabled for math)
-    if test -n "`$CC -dM -E - </dev/null | grep __SSE2_MATH__`"
-    then
-        ac_sse2_enabled=yes
-    else
-        ac_sse2_enabled=no
-    fi
-    AC_MSG_RESULT($ac_sse2_enabled)
-
-    # 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 $ac_sse2_enabled = no
+    # Check that it's okay to use gcc inline assembler to get and set
+    # x87 control word.  It should be, but you never know...
+    AC_MSG_CHECKING(whether we can use gcc inline assembler to get and set x87 control word)
+    AC_TRY_COMPILE([], [
+      unsigned short cw;
+      __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
+      __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
+    ],
+    [have_gcc_asm_for_x87=yes], [have_gcc_asm_for_x87=no])
+    AC_MSG_RESULT($have_gcc_asm_for_x87)
+    if test "$have_gcc_asm_for_x87" = yes
     then
-        # Check cpuid for SSE2 availability.  Bits 25 and 26 of edx tell
-        # us about SSE and SSE2 respectively.
-        AC_MSG_CHECKING(whether SSE2 instructions are available on this CPU)
-        AC_TRY_RUN([
-            int main() {
-                unsigned int ax, bx, cx, dx, func;
-                func = 1U;
-                __asm__ __volatile__ (
-                    "pushl %%ebx\n\t"  /* don't clobber ebx */
-                    "cpuid\n\t"
-                    "movl %%ebx, %1\n\t"
-                    "popl %%ebx"
-                    : "=a" (ax), "=r" (bx), "=c" (cx), "=d" (dx)
-                    : "a" (func)
-                    : "cc" );
-                if ((dx & (1U << 25)) && (dx & (1U << 26)))
-                    return 0;
-                else
-                    return 1;
-            }
-        ],
-        ac_cv_cpu_has_sse2=yes,
-        ac_cv_cpu_has_sse2=no,
-        ac_cv_cpu_has_sse2=no)
-        AC_MSG_RESULT($ac_cv_cpu_has_sse2)
-
-        # determine whether gcc accepts options to turn on SSE2
-        AC_MSG_CHECKING(whether $CC accepts -msse2 -mfpmath=sse)
-        ac_save_cc="$CC"
-        CC="$CC -msse2 -mfpmath=sse"
-        AC_TRY_RUN([int main() { return 0; }],
-        ac_cv_msse2_ok=yes,
-        ac_cv_msse2_ok=no,
-        ac_cv_msse2_ok=no)
-        CC="$ac_save_cc"
-        AC_MSG_RESULT($ac_cv_msse2_ok)
-
-        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
-            AC_DEFINE(USING_X87_FPU, 1,
-            [Define on x86 hardware if the x87 FPU is being used
-             for floating-point arithmetic])
-            AC_MSG_CHECKING(whether we can use gcc inline assembler to get and set x87 control word)
-            AC_TRY_COMPILE([], [
-              unsigned short cw;
-              __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
-              __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
-            ],
-            [have_gcc_asm_for_x87=yes], [have_gcc_asm_for_x87=no])
-            AC_MSG_RESULT($have_gcc_asm_for_x87)
-            if test "$have_gcc_asm_for_x87" = yes
-            then
-                AC_DEFINE(HAVE_GCC_ASM_FOR_X87, 1,
-                [Define if we can use gcc inline assembler to get and set x87 control word])
-            fi
-        fi
+        AC_DEFINE(HAVE_GCC_ASM_FOR_X87, 1,
+        [Define if we can use gcc inline assembler to get and set x87 control word])
     fi
 fi
 
diff --git a/pyconfig.h.in b/pyconfig.h.in
index 1807d80..01bc235 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -989,10 +989,6 @@
 /* Define if you want to use computed gotos in ceval.c. */
 #undef USE_COMPUTED_GOTOS
 
-/* Define on x86 hardware if the x87 FPU is being used for floating-point
-   arithmetic */
-#undef USING_X87_FPU
-
 /* Define if a va_list is an array of some kind */
 #undef VA_LIST_IS_ARRAY