[PATCH] initial i386-nacl target support for gas

[Roland McGrath <mcgrathr at google dot com>]

This patch adds initial support for the i386-nacl target to gas.  It's
already supported in BFD.  This is not everything that's needed to be
actually useful for building Native Client binaries, but it's a start.

I cleaned up md_section_align to use "if (constant)" instead of #if for
its sometimes-used code.  This is generally good practice that reduces
chances of bit rot in the code not used in many configurations, and it
also makes it easier and cleaner for a te-*.h file like mine to enable
this code.

Ok for trunk?


Thanks,
Roland


gas/
2012-01-20  Roland McGrath  <mcgrathr@google.com>

	* config/tc-i386.c (ALIGN_SECTION_P): New macro, define it if not
	already defined by the te-*.h file.
	(md_section_align): Use it.

	* configure.tgt (i386-*-nacl*): Match it.
	* config/te-nacl.h: New file.

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index dbac2ce..d9b70df 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -309,7 +309,8 @@ const char extra_symbol_chars[] = "*%-(["
      || ((defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF))	\
 	 && !defined (TE_GNU)				\
 	 && !defined (TE_LINUX)				\
- 	 && !defined (TE_NETWARE)			\
+	 && !defined (TE_NACL)				\
+	 && !defined (TE_NETWARE)			\
 	 && !defined (TE_FreeBSD)			\
 	 && !defined (TE_DragonFly)			\
 	 && !defined (TE_NetBSD)))
@@ -8880,25 +8881,32 @@ md_undefined_symbol (char *name)
   return 0;
 }
 
+/* If ALIGN_SECTION_P evaluates to nonzero, we'll explicit pad out
+   a section to its alignment, as if it had ended with a .align directive.  */
+#ifndef ALIGN_SECTION_P
+# if (defined (OBJ_AOUT) || defined (OBJ_MAYBE_AOUT))
+/* For a.out, force the section size to be aligned.  If we don't do this,
+   BFD will align it for us, but it will not write out the final bytes of
+   the section.  This may be a bug in BFD, but it is easier to fix it here
+   since that is how the other a.out targets work.  */
+#  define ALIGN_SECTION_P (OUTPUT_FLAVOR == bfd_target_aout_flavour)
+# else
+#  define ALIGN_SECTION_P 0
+# endif
+#endif
+
 /* Round up a section size to the appropriate boundary.  */
 
 valueT
-md_section_align (segT segment ATTRIBUTE_UNUSED, valueT size)
+md_section_align (segT segment, valueT size)
 {
-#if (defined (OBJ_AOUT) || defined (OBJ_MAYBE_AOUT))
-  if (OUTPUT_FLAVOR == bfd_target_aout_flavour)
+  if (ALIGN_SECTION_P)
     {
-      /* For a.out, force the section size to be aligned.  If we don't do
-	 this, BFD will align it for us, but it will not write out the
-	 final bytes of the section.  This may be a bug in BFD, but it is
-	 easier to fix it here since that is how the other a.out targets
-	 work.  */
       int align;
 
       align = bfd_get_section_alignment (stdoutput, segment);
       size = ((size + (1 << align) - 1) & ((valueT) -1 << align));
     }
-#endif
 
   return size;
 }
diff --git a/gas/config/tc-i386.h b/gas/config/tc-i386.h
index 6a6b31d..688c69a 100644
--- a/gas/config/tc-i386.h
+++ b/gas/config/tc-i386.h
@@ -1,6 +1,6 @@
 /* tc-i386.h -- Header file for tc-i386.c
    Copyright 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
    Free Software Foundation, Inc.
 
    This file is part of GAS, the GNU Assembler.
@@ -61,6 +61,8 @@ extern unsigned long i386_mach (void);
 #define ELF_TARGET_FORMAT64	"elf64-x86-64-freebsd"
 #elif defined (TE_VXWORKS)
 #define ELF_TARGET_FORMAT	"elf32-i386-vxworks"
+#elif defined (TE_NACL)
+#define ELF_TARGET_FORMAT	"elf32-i386-nacl"
 #endif
 
 #ifdef TE_SOLARIS
diff --git a/gas/config/te-nacl.h b/gas/config/te-nacl.h
new file mode 100644
index 0000000..17f3b5e
--- /dev/null
+++ b/gas/config/te-nacl.h
@@ -0,0 +1,29 @@
+/* Copyright 2012 Free Software Foundation, Inc.
+
+   This file is part of GAS, the GNU Assembler.
+
+   GAS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 3,
+   or (at your option) any later version.
+
+   GAS is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+   the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with GAS; see the file COPYING.  If not, write to the Free
+   Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
+   02110-1301, USA.  */
+
+#define TE_NACL
+#define LOCAL_LABELS_FB 1
+
+/* Align explicitly in the assembler so we always do it with nops.
+   Without this, we'd be relying on the linker to pad between input
+   sections.  But it doesn't always pad executable sections with nops,
+   sometimes with zero, which NaCl cannot accept.  */
+#define ALIGN_SECTION_P 1
+
+#include "obj-format.h"
diff --git a/gas/configure.tgt b/gas/configure.tgt
index 7090682..c33bb7a 100644
--- a/gas/configure.tgt
+++ b/gas/configure.tgt
@@ -181,6 +181,7 @@ case ${generic_target} in
   i386-*-elf)				fmt=elf ;;
   i386-*-kaos*)				fmt=elf ;;
   i386-*-bsd*)				fmt=aout em=386bsd ;;
+  i386-*-nacl*)				fmt=elf  em=nacl ;;
   i386-*-netbsd0.8)			fmt=aout em=386bsd ;;
   i386-*-netbsdpe*)			fmt=coff em=pe ;;
   i386-*-netbsd*-gnu* | \