Always support float128 on x86

Always support float128 on x86

[Joseph Myers]

In <https://gcc.gnu.org/ml/gcc-bugs/2016-08/msg03233.html>, Nick
reported i386-elf and ia64-elf failing to build because of
float128_type_node being NULL, but being used by the back end for
__float128.

The global float128_type_node is only available conditionally, if
target hooks indicate TFmode is not only available as a scalar mode
and of the right format, but also supported in libgcc.  The back-end
support, however, expects the type always to be available for
__float128 even if the libgcc support is missing.

Although a target-specific node could be restored in the case where
libgcc support is missing, it seems better to address the missing
libgcc support.  Thus, this patch enables TFmode soft-fp in libgcc
globally for all x86 targets - the only special cases needed being for
targets that use soft-fp for SFmode and DFmode, one of which already
had the support for TFmode as well (so I based the i[34567]86-*-rtems*
configuration on that present for i[34567]86-*-elfiamcu).  The i386
implementation of TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P is then
removed as no longer needed.

I can provide such a patch for ia64 if useful, but am not in a
position to test it (and while I'm reasonably confident that enabling
this support would be right for ia64-elf and ia64-freebsd, I've no
real idea if enabling libgcc support for TFmode, with or without also
enabling it for XFmode, would be safe for ia64-vms).

Bootstrapped with no regressions on x86_64-pc-linux-gnu.  OK to
commit?

gcc:
2016-08-25  Joseph Myers  <joseph@codesourcery.com>

	* config/i386/i386.c (ix86_libgcc_floating_mode_supported_p)
	(TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P): Remove.
	* config/i386/i386elf.h (IX86_MAYBE_NO_LIBGCC_TFMODE): Likewise.
	* config/i386/lynx.h (IX86_MAYBE_NO_LIBGCC_TFMODE): Likewise.
	* config/i386/netbsd-elf.h (IX86_MAYBE_NO_LIBGCC_TFMODE):
	Likewise.
	* config/i386/netbsd64.h (IX86_MAYBE_NO_LIBGCC_TFMODE): Likewise.
	* config/i386/nto.h (IX86_MAYBE_NO_LIBGCC_TFMODE): Likewise.
	* config/i386/openbsd.h (IX86_MAYBE_NO_LIBGCC_TFMODE): Likewise.
	* config/i386/rtemself.h (IX86_NO_LIBGCC_TFMODE): Likewise.
	* config/i386/vxworks.h (IX86_MAYBE_NO_LIBGCC_TFMODE): Likewise.

libgcc:
2016-08-25  Joseph Myers  <joseph@codesourcery.com>

	* config.host (i[34567]86-*-* | x86_64-*-*): Enable TFmode soft-fp
	where not already enabled.

Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c	(revision 239761)
+++ gcc/config/i386/i386.c	(working copy)
@@ -43284,31 +43284,6 @@
   return false;
 }
 
-/* Implement target hook libgcc_floating_mode_supported_p.  */
-static bool
-ix86_libgcc_floating_mode_supported_p (machine_mode mode)
-{
-  switch (mode)
-    {
-    case SFmode:
-    case DFmode:
-    case XFmode:
-      return true;
-
-    case TFmode:
-#ifdef IX86_NO_LIBGCC_TFMODE
-      return false;
-#elif defined IX86_MAYBE_NO_LIBGCC_TFMODE
-      return TARGET_LONG_DOUBLE_128;
-#else
-      return true;
-#endif
-
-    default:
-      return false;
-    }
-}
-
 /* Target hook for c_mode_for_suffix.  */
 static machine_mode
 ix86_c_mode_for_suffix (char suffix)
@@ -50568,10 +50543,6 @@
 #undef TARGET_VECTOR_MODE_SUPPORTED_P
 #define TARGET_VECTOR_MODE_SUPPORTED_P ix86_vector_mode_supported_p
 
-#undef TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P
-#define TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P \
-  ix86_libgcc_floating_mode_supported_p
-
 #undef TARGET_C_MODE_FOR_SUFFIX
 #define TARGET_C_MODE_FOR_SUFFIX ix86_c_mode_for_suffix
 
Index: gcc/config/i386/i386elf.h
===================================================================
--- gcc/config/i386/i386elf.h	(revision 239761)
+++ gcc/config/i386/i386elf.h	(working copy)
@@ -101,5 +101,3 @@
 #undef ASM_OUTPUT_ALIGNED_BSS
 #define ASM_OUTPUT_ALIGNED_BSS(FILE, DECL, NAME, SIZE, ALIGN) \
   asm_output_aligned_bss (FILE, DECL, NAME, SIZE, ALIGN)
-
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
Index: gcc/config/i386/lynx.h
===================================================================
--- gcc/config/i386/lynx.h	(revision 239761)
+++ gcc/config/i386/lynx.h	(working copy)
@@ -85,5 +85,3 @@
    TLS is detected by configure.  We undefine it here.  */
 
 #undef HAVE_AS_TLS
-
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
Index: gcc/config/i386/netbsd-elf.h
===================================================================
--- gcc/config/i386/netbsd-elf.h	(revision 239761)
+++ gcc/config/i386/netbsd-elf.h	(working copy)
@@ -119,5 +119,3 @@
 #define DEFAULT_PCC_STRUCT_RETURN 1
 
 #define HAVE_ENABLE_EXECUTE_STACK
-
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
Index: gcc/config/i386/netbsd64.h
===================================================================
--- gcc/config/i386/netbsd64.h	(revision 239761)
+++ gcc/config/i386/netbsd64.h	(working copy)
@@ -67,5 +67,3 @@
 }
 
 #define HAVE_ENABLE_EXECUTE_STACK
-
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
Index: gcc/config/i386/nto.h
===================================================================
--- gcc/config/i386/nto.h	(revision 239761)
+++ gcc/config/i386/nto.h	(working copy)
@@ -103,5 +103,3 @@
 #define TARGET_POSIX_IO
 
 #undef DBX_REGISTER_NUMBER
-
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
Index: gcc/config/i386/openbsd.h
===================================================================
--- gcc/config/i386/openbsd.h	(revision 239761)
+++ gcc/config/i386/openbsd.h	(working copy)
@@ -99,5 +99,3 @@
 #undef ASM_QUAD
 
 #define TARGET_HAVE_NAMED_SECTIONS false
-
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
Index: gcc/config/i386/rtemself.h
===================================================================
--- gcc/config/i386/rtemself.h	(revision 239761)
+++ gcc/config/i386/rtemself.h	(working copy)
@@ -31,5 +31,3 @@
 
 #undef LONG_DOUBLE_TYPE_SIZE
 #define LONG_DOUBLE_TYPE_SIZE (TARGET_80387 ? 80 : 64)
-
-#define IX86_NO_LIBGCC_TFMODE
Index: gcc/config/i386/vxworks.h
===================================================================
--- gcc/config/i386/vxworks.h	(revision 239761)
+++ gcc/config/i386/vxworks.h	(working copy)
@@ -87,8 +87,6 @@
    fixed gap between segments.  */
 #undef ASM_PREFERRED_EH_DATA_FORMAT
 
-#define IX86_MAYBE_NO_LIBGCC_TFMODE
-
 /* Define this to be nonzero if static stack checking is supported.  */
 #define STACK_CHECK_STATIC_BUILTIN 1
 
Index: libgcc/config.host
===================================================================
--- libgcc/config.host	(revision 239761)
+++ libgcc/config.host	(working copy)
@@ -632,7 +632,7 @@
 	extra_parts=crtbegin.o
 	;;
 i[34567]86-*-rtems*)
-	tmake_file="$tmake_file i386/t-crtstuff t-softfp-sfdf t-softfp"
+	tmake_file="$tmake_file i386/t-crtstuff t-softfp-sfdftf i386/32/t-softfp i386/t-softfp t-softfp"
 	extra_parts="$extra_parts crti.o crtn.o"
 	;;
 i[34567]86-*-solaris2* | x86_64-*-solaris2.1[0-9]*)
@@ -1330,17 +1330,10 @@
 esac
 
 case ${host} in
-i[34567]86-*-darwin* | x86_64-*-darwin* | \
-  i[34567]86-*-kfreebsd*-gnu | x86_64-*-kfreebsd*-gnu | \
-  i[34567]86-*-linux* | x86_64-*-linux* | \
-  i[34567]86-*-msdosdjgpp* | \
-  i[34567]86-*-gnu* | \
-  i[34567]86-*-solaris2* | x86_64-*-solaris2.1[0-9]* | \
-  i[34567]86-*-cygwin* | x86_64-*-cygwin* | \
-  i[34567]86-*-mingw* | x86_64-*-mingw* | \
-  i[34567]86-*-dragonfly* | x86_64-*-dragonfly* | \
-  i[34567]86-*-freebsd* | x86_64-*-freebsd* | \
-  i[34567]86-*-openbsd* | x86_64-*-openbsd*)
+i[34567]86-*-elfiamcu | i[34567]86-*-rtems*)
+	# These use soft-fp for SFmode and DFmode, not just TFmode.
+	;;
+i[34567]86-*-* | x86_64-*-*)
   	tmake_file="${tmake_file} t-softfp-tf"
 	if test "${host_address}" = 32; then
 		tmake_file="${tmake_file} i386/${host_address}/t-softfp"

-- 
Joseph S. Myers
joseph@codesourcery.com