Remove --with-fp / --without-fp.

There is a configure option --without-fp that specifies that nofpu
sysdeps directories should be used instead of fpu directories.

For most glibc configurations, this option is of no use: either there
is no valid nofpu variant of that configuration, or there are no fpu
or nofpu sysdeps directories for that processor and so the option does
nothing.  For a few configurations, if you are using a soft-float
compiler this option is required, and failing to use it generally
results in compilation errors from inline asm using unavailable
floating-point instructions.

We're moving away from --with-cpu to configuring glibc based on how
the compiler generates code, and it is natural to do so for
--without-fp as well; in most cases the soft-float and hard-float ABIs
are incompatible so you have no hope of building a working glibc with
an inappropriately configured compiler or libgcc.

This patch eliminates --without-fp, replacing it entirely by automatic
configuration based on the compiler.  Configurations for which this is
relevant (coldfire / mips / powerpc32 / sh) define a variable
with_fp_cond in their preconfigure fragments (under the same
conditions under which those fragments do anything); this is a
preprocessor conditional which the toplevel configure script then uses
in a test to determine which sysdeps directories to use.

The config.make with-fp variable remains.  It's used only by powerpc
(sysdeps/powerpc/powerpc32/Makefile) to add -mhard-float to various
flags variables.  For powerpc, -mcpu= options can imply use of
soft-float.  That could be an issue if you want to build for
e.g. 476fp, but are using --with-cpu=476 because there isn't a 476fp
sysdeps directory.  If in future we eliminate --with-cpu and replace
it entirely by testing the compiler, it would be natural at that point
to eliminate that code as well (as the user should then just use a
compiler defaulting to 476fp and the 476 sysdeps directory would be
used automatically).

Tested for x86_64, and tested with build-many-glibcs.py that installed
shared libraries are unchanged by this patch.

	* configure.ac (--with-fp): Remove configure option.
	(with_fp_cond): New variable.
	(libc_cv_with_fp): New configure test.  Use this variable instead
	of with_fp.
	* configure: Regenerated.
	* config.make.in (with-fp): Use @libc_cv_with_fp@.
	* manual/install.texi (Configuring and compiling): Remove
	--without-fp.
	* INSTALL: Regenerated.
	* sysdeps/m68k/preconfigure (with_fp_cond): Define for ColdFire.
	* sysdeps/mips/preconfigure (with_fp_cond): Define.
	* sysdeps/powerpc/preconfigure (with_fp_cond): Define for 32-bit.
	* sysdeps/sh/preconfigure (with_fp_cond): Define.
	* scripts/build-many-glibcs.py (Context.add_all_configs): Do not
	use --without-fp to configure glibc.

12 files changed, 112 insertions, 66 deletions

diff --git a/ChangeLog b/ChangeLog
index 90e47f7..7a54848 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2017-12-12  Joseph Myers  <joseph@codesourcery.com>
+
+	* configure.ac (--with-fp): Remove configure option.
+	(with_fp_cond): New variable.
+	(libc_cv_with_fp): New configure test.  Use this variable instead
+	of with_fp.
+	* configure: Regenerated.
+	* config.make.in (with-fp): Use @libc_cv_with_fp@.
+	* manual/install.texi (Configuring and compiling): Remove
+	--without-fp.
+	* INSTALL: Regenerated.
+	* sysdeps/m68k/preconfigure (with_fp_cond): Define for ColdFire.
+	* sysdeps/mips/preconfigure (with_fp_cond): Define.
+	* sysdeps/powerpc/preconfigure (with_fp_cond): Define for 32-bit.
+	* sysdeps/sh/preconfigure (with_fp_cond): Define.
+	* scripts/build-many-glibcs.py (Context.add_all_configs): Do not
+	use --without-fp to configure glibc.
+
 2017-12-12  Rical Jasan  <ricaljasan@pacific.net>
 
 	* manual/locale.texi (nl_langinfo): Fix a typo.
diff --git a/INSTALL b/INSTALL
index e59c11d..80306de 100644
--- a/INSTALL
+++ b/INSTALL
@@ -81,10 +81,6 @@ will be used, and CFLAGS sets optimization options for the compiler.
      library will still be usable, but functionality may be lost--for
      example, you can't build a shared libc with old binutils.
 
-'--without-fp'
-     Use this option if your computer lacks hardware floating-point
-     support and your operating system does not emulate an FPU.
-
 '--disable-shared'
      Don't build shared libraries even if it is possible.  Not all
      systems support shared libraries; you need ELF support and
diff --git a/NEWS b/NEWS
index 25a2116..c6d859c 100644
--- a/NEWS
+++ b/NEWS
@@ -76,6 +76,11 @@ Deprecated and removed features, and other changes affecting compatibility:
   glibc has been removed.  The --enable-add-ons configure option is now
   ignored.
 
+* The --without-fp configure option is now ignored.  Whether hardware
+  floating-point instructions are used is now configured based on whether
+  the compiler used at configure time (without any options implied by a
+  --with-cpu= configure option) uses such instructions.
+
 * The res_hnok, res_dnok, res_mailok and res_ownok functions now check that
   the specified string can be parsed as a domain name.
 
diff --git a/config.make.in b/config.make.in
index 9da77d1..04513db 100644
--- a/config.make.in
+++ b/config.make.in
@@ -57,7 +57,7 @@ have-z-execstack = @libc_cv_z_execstack@
 have-protected-data = @libc_cv_protected_data@
 have-insert = @libc_cv_insert@
 have-glob-dat-reloc = @libc_cv_has_glob_dat@
-with-fp = @with_fp@
+with-fp = @libc_cv_with_fp@
 enable-timezone-tools = @enable_timezone_tools@
 unwind-find-fde = @libc_cv_gcc_unwind_find_fde@
 have-fpie = @libc_cv_fpie@
diff --git a/configure b/configure
index dd8b8c9..4a85706 100755
--- a/configure
+++ b/configure
@@ -666,6 +666,7 @@ multi_arch
 no_stack_protector
 stack_protector
 libc_cv_ssp
+libc_cv_with_fp
 base_machine
 have_tunables
 build_pt_chown
@@ -683,7 +684,6 @@ hardcoded_path_in_tests
 enable_timezone_tools
 use_default_link
 sysheaders
-with_fp
 ac_ct_CXX
 CXXFLAGS
 CXX
@@ -756,7 +756,6 @@ with_bugurl
 with_gd
 with_gd_include
 with_gd_lib
-with_fp
 with_binutils
 with_selinux
 with_headers
@@ -1467,7 +1466,6 @@ Optional Packages:
   --with-gd=DIR           find libgd include dir and library with prefix DIR
   --with-gd-include=DIR   find libgd include files in DIR
   --with-gd-lib=DIR       find libgd library files in DIR
-  --with-fp               if using floating-point hardware [default=yes]
   --with-binutils=PATH    specify location of binutils (as and ld)
   --with-selinux          if building with SELinux support
   --with-headers=PATH     location of system headers to use (for example
@@ -3294,15 +3292,6 @@ libgd-LDFLAGS = $libgd_ldflags"
 fi
 
 
-# Check whether --with-fp was given.
-if test "${with_fp+set}" = set; then :
-  withval=$with_fp; with_fp=$withval
-else
-  with_fp=yes
-fi
-
-
-
 # Check whether --with-binutils was given.
 if test "${with_binutils+set}" = set; then :
   withval=$with_binutils; path_binutils=$withval
@@ -3778,6 +3767,11 @@ fi
 # check below.
 libc_config_ok=no
 
+# A preconfigure script for a system that may or may not use fpu
+# sysdeps directories sets this to a preprocessor conditional for
+# whether to use such directories.
+with_fp_cond=1
+
 if frags=`ls -d $srcdir/sysdeps/*/preconfigure 2> /dev/null`
 then
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sysdeps preconfigure fragments" >&5
@@ -3816,6 +3810,30 @@ fi
 test -n "$base_machine" || base_machine=$machine
 
 
+# Determine whether to use fpu or nofpu sysdeps directories.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for use of fpu sysdeps directories" >&5
+$as_echo_n "checking for use of fpu sysdeps directories... " >&6; }
+if ${libc_cv_with_fp+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest.c <<EOF
+#if $with_fp_cond
+int dummy;
+#else
+# error "no hardware floating point"
+#endif
+EOF
+libc_cv_with_fp=no
+if ${CC-cc} $CFLAGS $CPPFLAGS -S conftest.c -o conftest.s \
+   1>&5 2>&5 ; then
+  libc_cv_with_fp=yes
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_with_fp" >&5
+$as_echo "$libc_cv_with_fp" >&6; }
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for -fstack-protector" >&5
 $as_echo_n "checking for -fstack-protector... " >&6; }
 if ${libc_cv_ssp+:} false; then :
@@ -4085,7 +4103,7 @@ tail=$machine${submachine:+/$submachine}
 while m=`echo $tail | sed 's@^\(.*\)/\([^/]*\)$@& \1@'`; test -n "$m"; do
   set $m
   # Prepend the machine's FPU directory unless --without-fp.
-  if test "$with_fp" = yes; then
+  if test "$libc_cv_with_fp" = yes; then
     maybe_fpu=/fpu
   else
     maybe_fpu=/nofpu
diff --git a/configure.ac b/configure.ac
index f85a50d..edf6627 100644
--- a/configure.ac
+++ b/configure.ac
@@ -127,12 +127,6 @@ libgd-LDFLAGS = $libgd_ldflags"
 fi
 
 dnl Arguments to specify presence of other packages/features.
-AC_ARG_WITH([fp],
-	    AC_HELP_STRING([--with-fp],
-			   [if using floating-point hardware @<:@default=yes@:>@]),
-	    [with_fp=$withval],
-	    [with_fp=yes])
-AC_SUBST(with_fp)
 AC_ARG_WITH([binutils],
 	    AC_HELP_STRING([--with-binutils=PATH],
 			   [specify location of binutils (as and ld)]),
@@ -489,6 +483,11 @@ AC_ARG_WITH([cpu],
 # check below.
 libc_config_ok=no
 
+# A preconfigure script for a system that may or may not use fpu
+# sysdeps directories sets this to a preprocessor conditional for
+# whether to use such directories.
+with_fp_cond=1
+
 dnl Let sysdeps/*/preconfigure act here.
 LIBC_PRECONFIGURE([$srcdir], [for sysdeps])
 
@@ -517,6 +516,24 @@ fi
 test -n "$base_machine" || base_machine=$machine
 AC_SUBST(base_machine)
 
+# Determine whether to use fpu or nofpu sysdeps directories.
+AC_CACHE_CHECK([for use of fpu sysdeps directories],
+	       libc_cv_with_fp, [dnl
+cat > conftest.c <<EOF
+#if $with_fp_cond
+int dummy;
+#else
+# error "no hardware floating point"
+#endif
+EOF
+libc_cv_with_fp=no
+if ${CC-cc} $CFLAGS $CPPFLAGS -S conftest.c -o conftest.s \
+   1>&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD ; then
+  libc_cv_with_fp=yes
+fi
+rm -f conftest*])
+AC_SUBST(libc_cv_with_fp)
+
 AC_CACHE_CHECK(for -fstack-protector, libc_cv_ssp, [dnl
 LIBC_TRY_CC_OPTION([$CFLAGS $CPPFLAGS -Werror -fstack-protector],
 		   [libc_cv_ssp=yes],
@@ -720,7 +737,7 @@ tail=$machine${submachine:+/$submachine}
 while m=`echo $tail | sed 's@^\(.*\)/\([^/]*\)$@& \1@'`; test -n "$m"; do
   set $m
   # Prepend the machine's FPU directory unless --without-fp.
-  if test "$with_fp" = yes; then
+  if test "$libc_cv_with_fp" = yes; then
     maybe_fpu=/fpu
   else
     maybe_fpu=/nofpu
diff --git a/manual/install.texi b/manual/install.texi
index a3cb09d..e81f1c5 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -106,10 +106,6 @@ problem and suppress these constructs, so that the library will still be
 usable, but functionality may be lost---for example, you can't build a
 shared libc with old binutils.
 
-@item --without-fp
-Use this option if your computer lacks hardware floating-point support
-and your operating system does not emulate an FPU.
-
 @c disable static doesn't work currently
 @c @item --disable-static
 @c Don't build static libraries.  Static libraries aren't that useful these
diff --git a/scripts/build-many-glibcs.py b/scripts/build-many-glibcs.py
index 59972a0..599e12e 100755
--- a/scripts/build-many-glibcs.py
+++ b/scripts/build-many-glibcs.py
@@ -216,15 +216,12 @@ class Context(object):
                         os_name='linux-gnu',
                         variant='soft',
                         gcc_cfg=['--with-mips-plt', '--with-float=soft'],
-                        glibcs=[{'variant': 'n32-soft',
-                                 'cfg': ['--without-fp']},
+                        glibcs=[{'variant': 'n32-soft'},
                                 {'variant': 'soft',
                                  'arch': 'mips',
-                                 'ccopts': '-mabi=32',
-                                 'cfg': ['--without-fp']},
+                                 'ccopts': '-mabi=32'},
                                 {'variant': 'n64-soft',
-                                 'ccopts': '-mabi=64',
-                                 'cfg': ['--without-fp']}])
+                                 'ccopts': '-mabi=64'}])
         self.add_config(arch='mips64',
                         os_name='linux-gnu',
                         variant='nan2008',
@@ -244,15 +241,12 @@ class Context(object):
                                  '--with-arch-64=mips64r2',
                                  '--with-arch-32=mips32r2',
                                  '--with-float=soft'],
-                        glibcs=[{'variant': 'n32-nan2008-soft',
-                                 'cfg': ['--without-fp']},
+                        glibcs=[{'variant': 'n32-nan2008-soft'},
                                 {'variant': 'nan2008-soft',
                                  'arch': 'mips',
-                                 'ccopts': '-mabi=32',
-                                 'cfg': ['--without-fp']},
+                                 'ccopts': '-mabi=32'},
                                 {'variant': 'n64-nan2008-soft',
-                                 'ccopts': '-mabi=64',
-                                 'cfg': ['--without-fp']}])
+                                 'ccopts': '-mabi=64'}])
         self.add_config(arch='mips64el',
                         os_name='linux-gnu',
                         gcc_cfg=['--with-mips-plt'],
@@ -265,15 +259,12 @@ class Context(object):
                         os_name='linux-gnu',
                         variant='soft',
                         gcc_cfg=['--with-mips-plt', '--with-float=soft'],
-                        glibcs=[{'variant': 'n32-soft',
-                                 'cfg': ['--without-fp']},
+                        glibcs=[{'variant': 'n32-soft'},
                                 {'variant': 'soft',
                                  'arch': 'mipsel',
-                                 'ccopts': '-mabi=32',
-                                 'cfg': ['--without-fp']},
+                                 'ccopts': '-mabi=32'},
                                 {'variant': 'n64-soft',
-                                 'ccopts': '-mabi=64',
-                                 'cfg': ['--without-fp']}])
+                                 'ccopts': '-mabi=64'}])
         self.add_config(arch='mips64el',
                         os_name='linux-gnu',
                         variant='nan2008',
@@ -293,15 +284,12 @@ class Context(object):
                                  '--with-arch-64=mips64r2',
                                  '--with-arch-32=mips32r2',
                                  '--with-float=soft'],
-                        glibcs=[{'variant': 'n32-nan2008-soft',
-                                 'cfg': ['--without-fp']},
+                        glibcs=[{'variant': 'n32-nan2008-soft'},
                                 {'variant': 'nan2008-soft',
                                  'arch': 'mipsel',
-                                 'ccopts': '-mabi=32',
-                                 'cfg': ['--without-fp']},
+                                 'ccopts': '-mabi=32'},
                                 {'variant': 'n64-nan2008-soft',
-                                 'ccopts': '-mabi=64',
-                                 'cfg': ['--without-fp']}])
+                                 'ccopts': '-mabi=64'}])
         self.add_config(arch='nios2',
                         os_name='linux-gnu')
         self.add_config(arch='powerpc',
@@ -314,8 +302,7 @@ class Context(object):
                         os_name='linux-gnu',
                         variant='soft',
                         gcc_cfg=['--disable-multilib', '--with-float=soft',
-                                 '--enable-secureplt'],
-                        glibcs=[{'variant': 'soft', 'cfg': ['--without-fp']}])
+                                 '--enable-secureplt'])
         self.add_config(arch='powerpc64',
                         os_name='linux-gnu',
                         gcc_cfg=['--disable-multilib', '--enable-secureplt'])
@@ -325,13 +312,11 @@ class Context(object):
         self.add_config(arch='powerpc',
                         os_name='linux-gnuspe',
                         gcc_cfg=['--disable-multilib', '--enable-secureplt',
-                                 '--enable-e500-double'],
-                        glibcs=[{'cfg': ['--without-fp']}])
+                                 '--enable-e500-double'])
         self.add_config(arch='powerpc',
                         os_name='linux-gnuspe',
                         variant='e500v1',
-                        gcc_cfg=['--disable-multilib', '--enable-secureplt'],
-                        glibcs=[{'variant': 'e500v1', 'cfg': ['--without-fp']}])
+                        gcc_cfg=['--disable-multilib', '--enable-secureplt'])
         self.add_config(arch='s390x',
                         os_name='linux-gnu',
                         glibcs=[{},
@@ -347,13 +332,11 @@ class Context(object):
         self.add_config(arch='sh4',
                         os_name='linux-gnu',
                         variant='soft',
-                        gcc_cfg=['--without-fp'],
-                        glibcs=[{'variant': 'soft', 'cfg': ['--without-fp']}])
+                        gcc_cfg=['--without-fp'])
         self.add_config(arch='sh4eb',
                         os_name='linux-gnu',
                         variant='soft',
-                        gcc_cfg=['--without-fp'],
-                        glibcs=[{'variant': 'soft', 'cfg': ['--without-fp']}])
+                        gcc_cfg=['--without-fp'])
         self.add_config(arch='sparc64',
                         os_name='linux-gnu',
                         glibcs=[{},
diff --git a/sysdeps/m68k/preconfigure b/sysdeps/m68k/preconfigure
index 94fc1aa..1028dac 100644
--- a/sysdeps/m68k/preconfigure
+++ b/sysdeps/m68k/preconfigure
@@ -13,5 +13,9 @@ m68k)		variant=`(echo "#ifdef __mcoldfire__"
 		  echo >&2 "Cannot determine m68k processor variant"
 		  exit 1
 		fi
-		base_machine=m68k machine=m68k/$variant ;;
+		base_machine=m68k machine=m68k/$variant
+		if test "$variant" = "coldfire"; then
+		  with_fp_cond="defined __mcffpu__"
+		fi
+		;;
 esac
diff --git a/sysdeps/mips/preconfigure b/sysdeps/mips/preconfigure
index c118592..48fc32e 100644
--- a/sysdeps/mips/preconfigure
+++ b/sysdeps/mips/preconfigure
@@ -25,5 +25,7 @@ mips*)
 	if test "$abiflag" != "_ABIO32" -a "$mips16flag" = "1"; then
 		as_fn_error $? "MIPS16 is only supported with the o32 ABI." "$LINENO" 5
 	fi
+
+	with_fp_cond="defined __mips_hard_float"
 	;;
 esac
diff --git a/sysdeps/powerpc/preconfigure b/sysdeps/powerpc/preconfigure
index 7de2eaf..0030bfd 100644
--- a/sysdeps/powerpc/preconfigure
+++ b/sysdeps/powerpc/preconfigure
@@ -16,5 +16,6 @@ powerpc*)
     base_machine=powerpc machine=powerpc/powerpc32
   fi
   rm -f conftest.i
+  with_fp_cond="!defined __NO_FPRS__"
   ;;
 esac
diff --git a/sysdeps/sh/preconfigure b/sysdeps/sh/preconfigure
index c1f6537..16e2927 100644
--- a/sysdeps/sh/preconfigure
+++ b/sysdeps/sh/preconfigure
@@ -1,6 +1,12 @@
 # preconfigure fragment for sh.
 
 case "$machine" in
-sh3*)		base_machine=sh machine=sh/sh3 ;;
-sh4*)		base_machine=sh machine=sh/sh4 ;;
+sh3*)		base_machine=sh
+		machine=sh/sh3
+		with_fp_cond="defined __SH_FPU_ANY__"
+		;;
+sh4*)		base_machine=sh
+		machine=sh/sh4
+		with_fp_cond="defined __SH_FPU_ANY__"
+		;;
 esac