The SSE2 detection and enabling could potentially cause

mdickinson · mdickinson · commit 7abf8d4066e9 · 2009-04-18T20:17:52.000Z
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.
diff --git 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
@@ -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
@@ -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
@@ -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
@@ -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
diff --git a/pyconfig.h.in b/pyconfig.h.in

Original file line number	Diff line number	Diff line change
`@@ -13,8 +13,7 @@ double _Py_force_double(double x)`
`13`	`13`	`}`
`14`	`14`	`#endif`
`15`	`15`
`16`		`-#ifdef USING_X87_FPU`
`17`		`-# ifdef HAVE_GCC_ASM_FOR_X87`
	`16`	`+#ifdef HAVE_GCC_ASM_FOR_X87`
`18`	`17`
`19`	`18`	`/* inline assembly for getting and setting the 387 FPU control word on`
`20`	`19`	`gcc/x86 */`
`@@ -29,9 +28,6 @@ void _Py_set_387controlword(unsigned short cw) {`
`29`	`28`	`__asm__ __volatile__ ("fldcw %0" : : "m" (cw));`
`30`	`29`	`}`
`31`	`30`
`32`		`-# else`
`33`		`-# error "Unable to get and set x87 control word"`
`34`		`-# endif`
`35`	`31`	`#endif`
`36`	`32`
`37`	`33`