Re: PATCH [1/n] X32: Add initial -x32 support

["H.J. Lu" <hjl.tools@gmail.com>]

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On Wed, Jul 6, 2011 at 8:02 AM, Richard Guenther
<richard.guenther@gmail.com> wrote:
> On Wed, Jul 6, 2011 at 4:48 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> Hi Paolo, DJ, Nathanael, Alexandre, Ralf,
>>
>> Is the change
>> .
>>        * configure.ac: Support --enable-x32.
>>        * configure: Regenerated.
>>
>> diff --git a/gcc/configure.ac b/gcc/configure.ac
>> index 5f3641b..bddabeb 100644
>> --- a/gcc/configure.ac
>> +++ b/gcc/configure.ac
>> @@ -611,6 +611,11 @@ AC_ARG_ENABLE(multilib,
>>  [], [enable_multilib=yes])
>>  AC_SUBST(enable_multilib)
>>
>> +# With x32 support
>> +AC_ARG_ENABLE(x32,
>> +[  --enable-x32            enable x32 library support for multiple ABIs],
>
> Looks like a very very generic switch for a global configury ... we already
> have --with-multilib-list (SH only), why not extend that to also work
> for x86_64?
>
> Richard.
>
>> +[], [enable_x32=no])
>> +
>>  # Enable __cxa_atexit for C++.
>>  AC_ARG_ENABLE(__cxa_atexit,
>>  [AS_HELP_STRING([--enable-__cxa_atexit], [enable __cxa_atexit for C++])],
>>
>> OK?
>>
>> Thanks.
>>

Here is the updated patch to use --with-multilib-list=x32.

Paolo, DJ, Nathanael, Alexandre, Ralf, Is the configure.ac change

---
	* configure.ac: Mention x86-64 for --with-multilib-list.
	* configure: Regenerated.

	* doc/install.texi: Document --with-multilib-list=x32.

diff --git a/gcc/configure.ac b/gcc/configure.ac
index 5f3641b..a73f758 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -795,7 +795,7 @@ esac],
 [enable_languages=c])

 AC_ARG_WITH(multilib-list,
-[AS_HELP_STRING([--with-multilib-list], [select multilibs (SH only)])],
+[AS_HELP_STRING([--with-multilib-list], [select multilibs (SH and
x86-64 only)])],
 :,
 with_multilib_list=default)

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 49aac95..a5d266c 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1049,8 +1049,10 @@ sysv, aix.
 @item --with-multilib-list=@var{list}
 @itemx --without-multilib-list
 Specify what multilibs to build.
-Currently only implemented for sh*-*-*.
+Currently only implemented for sh*-*-* and x86-64-*-linux*.

+@table @code
+@item sh*-*-*
 @var{list} is a comma separated list of CPU names.  These must be of the
 form @code{sh*} or @code{m*} (in which case they match the compiler option
 for that processor).  The list should not contain any endian options -
@@ -1082,6 +1084,12 @@ only little endian SH4AL:
 --with-multilib-list=sh4al,!mb/m4al
 @end smallexample

+@item x86-64-*-linux*
+If @var{list} is @code{x32}, x32 run-time library will be enabled.  By
+default, x32 run-time library is disabled.
+
+@end table
+
 @item --with-endian=@var{endians}
 Specify what endians to use.
 Currently only implemented for sh*-*-*.
---

OK?

Thanks.

-- 
H.J.
---
2011-07-06  H.J. Lu  <hongjiu.lu@intel.com>

	* config.gcc: Support --with-multilib-list=x32 for x86 Linux
	targets.

	* configure.ac: Mention x86-64 for --with-multilib-list.
	* configure: Regenerated.

	* config/i386/gnu-user64.h (SPEC_64): Support x32.
	(SPEC_32): Likewise.
	(ASM_SPEC): Likewise.
	(LINK_SPEC): Likewise.
	(TARGET_THREAD_SSP_OFFSET): Likewise.
	(TARGET_THREAD_SPLIT_STACK_OFFSET): Likewise.
	(SPEC_X32): New.

	* config/i386/i386.h (TARGET_X32): New.
	(TARGET_LP64): New.
	(LONG_TYPE_SIZE): Likewise.
	(POINTER_SIZE): Likewise.
	(POINTERS_EXTEND_UNSIGNED): Likewise.
	(OPT_ARCH64): Support x32.
	(OPT_ARCH32): Likewise.

	* config/i386/i386.opt (mx32): New.

	* config/i386/kfreebsd-gnu64.h (GNU_USER_LINK_EMULATIONX32): New.
	(GLIBC_DYNAMIC_LINKERX32): Likewise.
	* config/i386/linux64.h (GNU_USER_LINK_EMULATIONX32): Likewise.
	(GLIBC_DYNAMIC_LINKERX32): Likewise.

	* config/i386/t-linux-x32: New.

	* config/linux.h (UCLIBC_DYNAMIC_LINKERX32): New.
	(BIONIC_DYNAMIC_LINKERX32): Likewise.
	(GNU_USER_DYNAMIC_LINKERX32): Likewise.

	* doc/install.texi: Document --with-multilib-list=x32.

	* doc/invoke.texi: Document -mx32.

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2011-07-06  H.J. Lu  <hongjiu.lu@intel.com>

	* config.gcc: Support --with-multilib-list=x32 for x86 Linux
	targets.

	* configure.ac: Mention x86-64 for --with-multilib-list.
	* configure: Regenerated.

	* config/i386/gnu-user64.h (SPEC_64): Support x32.
	(SPEC_32): Likewise.
	(ASM_SPEC): Likewise.
	(LINK_SPEC): Likewise.
	(TARGET_THREAD_SSP_OFFSET): Likewise.
	(TARGET_THREAD_SPLIT_STACK_OFFSET): Likewise.
	(SPEC_X32): New.

	* config/i386/i386.h (TARGET_X32): New.
	(TARGET_LP64): New.
	(LONG_TYPE_SIZE): Likewise.
	(POINTER_SIZE): Likewise.
	(POINTERS_EXTEND_UNSIGNED): Likewise.
	(OPT_ARCH64): Support x32.
	(OPT_ARCH32): Likewise.

	* config/i386/i386.opt (mx32): New.

	* config/i386/kfreebsd-gnu64.h (GNU_USER_LINK_EMULATIONX32): New.
	(GLIBC_DYNAMIC_LINKERX32): Likewise.
	* config/i386/linux64.h (GNU_USER_LINK_EMULATIONX32): Likewise.
	(GLIBC_DYNAMIC_LINKERX32): Likewise.

	* config/i386/t-linux-x32: New.

	* config/linux.h (UCLIBC_DYNAMIC_LINKERX32): New.
	(BIONIC_DYNAMIC_LINKERX32): Likewise.
	(GNU_USER_DYNAMIC_LINKERX32): Likewise.

	* doc/install.texi: Document --with-multilib-list=x32.

	* doc/invoke.texi: Document -mx32.

diff --git a/gcc/config.gcc b/gcc/config.gcc
index c77f40b..2622046 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1279,7 +1279,11 @@ i[34567]86-*-linux* | i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-knetbsd*-gnu | i
 		if test x$enable_targets = xall; then
 			tm_file="${tm_file} i386/x86-64.h i386/gnu-user64.h i386/linux64.h"
 			tm_defines="${tm_defines} TARGET_BI_ARCH=1"
-			tmake_file="${tmake_file} i386/t-linux64"
+			if test x${with_multilib_list} = xx32; then
+				tmake_file="${tmake_file} i386/t-linux-x32"
+			else
+				tmake_file="${tmake_file} i386/t-linux64"
+			fi
 			need_64bit_hwint=yes
 			need_64bit_isa=yes
 			case X"${with_cpu}" in
@@ -1317,7 +1321,12 @@ x86_64-*-linux* | x86_64-*-kfreebsd*-gnu | x86_64-*-knetbsd*-gnu)
 	x86_64-*-kfreebsd*-gnu) tm_file="${tm_file} kfreebsd-gnu.h i386/kfreebsd-gnu64.h" ;;
 	x86_64-*-knetbsd*-gnu) tm_file="${tm_file} knetbsd-gnu.h" ;;
 	esac
-	tmake_file="${tmake_file} i386/t-linux64 i386/t-crtstuff i386/t-crtpc i386/t-crtfm t-dfprules"
+	if test x${with_multilib_list} = xx32; then
+		tmake_file="${tmake_file} i386/t-linux-x32"
+	else
+		tmake_file="${tmake_file} i386/t-linux64"
+	fi
+	tmake_file="${tmake_file} i386/t-crtstuff i386/t-crtpc i386/t-crtfm t-dfprules"
 	;;
 i[34567]86-pc-msdosdjgpp*)
 	xm_file=i386/xm-djgpp.h
diff --git a/gcc/config/i386/gnu-user64.h b/gcc/config/i386/gnu-user64.h
index b069975..954f3b2 100644
--- a/gcc/config/i386/gnu-user64.h
+++ b/gcc/config/i386/gnu-user64.h
@@ -58,25 +58,31 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #if TARGET_64BIT_DEFAULT
 #define SPEC_32 "m32"
-#define SPEC_64 "!m32"
+#define SPEC_64 "m32|mx32:;"
+#define SPEC_X32 "mx32"
 #else
-#define SPEC_32 "!m64"
+#define SPEC_32 "m64|mx32:;"
 #define SPEC_64 "m64"
+#define SPEC_X32 "mx32"
 #endif
 
 #undef ASM_SPEC
-#define ASM_SPEC "%{" SPEC_32 ":--32} %{" SPEC_64 ":--64} \
+#define ASM_SPEC "%{" SPEC_32 ":--32} \
+ %{" SPEC_64 ":--64} \
+ %{" SPEC_X32 ":--x32} \
  %{!mno-sse2avx:%{mavx:-msse2avx}} %{msse2avx:%{!mavx:-msse2avx}}"
 
 #undef	LINK_SPEC
 #define LINK_SPEC "%{" SPEC_64 ":-m " GNU_USER_LINK_EMULATION64 "} \
                    %{" SPEC_32 ":-m " GNU_USER_LINK_EMULATION32 "} \
+                   %{" SPEC_X32 ":-m " GNU_USER_LINK_EMULATIONX32 "} \
   %{shared:-shared} \
   %{!shared: \
     %{!static: \
       %{rdynamic:-export-dynamic} \
       %{" SPEC_32 ":-dynamic-linker " GNU_USER_DYNAMIC_LINKER32 "} \
-      %{" SPEC_64 ":-dynamic-linker " GNU_USER_DYNAMIC_LINKER64 "}} \
+      %{" SPEC_64 ":-dynamic-linker " GNU_USER_DYNAMIC_LINKER64 "} \
+      %{" SPEC_X32 ":-dynamic-linker " GNU_USER_DYNAMIC_LINKERX32 "}} \
     %{static:-static}}"
 
 /* Similar to standard GNU userspace, but adding -ffast-math support.  */
@@ -110,10 +116,13 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #ifdef TARGET_LIBC_PROVIDES_SSP
 /* i386 glibc provides __stack_chk_guard in %gs:0x14,
+   x32 glibc provides it in %fs:0x18. 
    x86_64 glibc provides it in %fs:0x28.  */
-#define TARGET_THREAD_SSP_OFFSET	(TARGET_64BIT ? 0x28 : 0x14)
+#define TARGET_THREAD_SSP_OFFSET \
+  (TARGET_64BIT ? (TARGET_X32 ? 0x18 : 0x28) : 0x14)
 
 /* We steal the last transactional memory word.  */
 #define TARGET_CAN_SPLIT_STACK
-#define TARGET_THREAD_SPLIT_STACK_OFFSET (TARGET_64BIT ? 0x70 : 0x30)
+#define TARGET_THREAD_SPLIT_STACK_OFFSET \
+  (TARGET_64BIT ? (TARGET_X32 ? 0x40 : 0x70) : 0x30)
 #endif
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index a1ac6b6..8cef4e7 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -42,6 +42,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 /* Redefines for option macros.  */
 
 #define TARGET_64BIT	OPTION_ISA_64BIT
+#define TARGET_X32	OPTION_ISA_X32
 #define TARGET_MMX	OPTION_ISA_MMX
 #define TARGET_3DNOW	OPTION_ISA_3DNOW
 #define TARGET_3DNOW_A	OPTION_ISA_3DNOW_A
@@ -72,6 +73,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define TARGET_RDRND	OPTION_ISA_RDRND
 #define TARGET_F16C	OPTION_ISA_F16C
 
+#define TARGET_LP64	(TARGET_64BIT && !TARGET_X32)
 
 /* SSE4.1 defines round instructions */
 #define	OPTION_MASK_ISA_ROUND	OPTION_MASK_ISA_SSE4_1
@@ -516,8 +518,8 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
 #define OPT_ARCH64 "!m32"
 #define OPT_ARCH32 "m32"
 #else
-#define OPT_ARCH64 "m64"
-#define OPT_ARCH32 "!m64"
+#define OPT_ARCH64 "m64|mx32"
+#define OPT_ARCH32 "m64|mx32:;"
 #endif
 
 /* Support for configure-time defaults of some command line options.
@@ -637,6 +639,8 @@ enum target_cpu_default
 
 #define SHORT_TYPE_SIZE 16
 #define INT_TYPE_SIZE 32
+#define LONG_TYPE_SIZE (TARGET_X32 ? 32 : BITS_PER_WORD)
+#define POINTER_SIZE (TARGET_X32 ? 32 : BITS_PER_WORD)
 #define LONG_LONG_TYPE_SIZE 64
 #define FLOAT_TYPE_SIZE 32
 #define DOUBLE_TYPE_SIZE 64
@@ -1742,6 +1746,13 @@ do {							\
    between pointers and any other objects of this machine mode.  */
 #define Pmode (TARGET_64BIT ? DImode : SImode)
 
+/* A C expression whose value is zero if pointers that need to be extended
+   from being `POINTER_SIZE' bits wide to `Pmode' are sign-extended and
+   greater then zero if they are zero-extended and less then zero if the
+   ptr_extend instruction should be used.  */
+
+#define POINTERS_EXTEND_UNSIGNED 1
+
 /* A function address in a call instruction
    is a byte address (for indexing purposes)
    so give the MEM rtx a byte's mode.  */
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index 9886b7b..8dea93e 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -398,9 +398,13 @@ Target RejectNegative Negative(m64) Report InverseMask(ISA_64BIT) Var(ix86_isa_f
 Generate 32bit i386 code
 
 m64
-Target RejectNegative Negative(m32) Report Mask(ISA_64BIT) Var(ix86_isa_flags) Save
+Target RejectNegative Negative(mx32) Report Mask(ISA_64BIT) Var(ix86_isa_flags) Save
 Generate 64bit x86-64 code
 
+mx32
+Target RejectNegative Negative(m32) Report Mask(ISA_X32) Var(ix86_isa_flags) Save
+Generate 32bit x86-64 code
+
 mmmx
 Target Report Mask(ISA_MMX) Var(ix86_isa_flags) Save
 Support MMX built-in functions
diff --git a/gcc/config/i386/kfreebsd-gnu64.h b/gcc/config/i386/kfreebsd-gnu64.h
index c3798a5..2085ca5 100644
--- a/gcc/config/i386/kfreebsd-gnu64.h
+++ b/gcc/config/i386/kfreebsd-gnu64.h
@@ -21,6 +21,8 @@ along with GCC; see the file COPYING3.  If not see
 
 #define GNU_USER_LINK_EMULATION32 "elf_i386_fbsd"
 #define GNU_USER_LINK_EMULATION64 "elf_x86_64_fbsd"
+#define GNU_USER_LINK_EMULATIONX32 "elf32_x86_64_fbsd"
 
 #define GLIBC_DYNAMIC_LINKER32 "/lib/ld.so.1"
 #define GLIBC_DYNAMIC_LINKER64 "/lib/ld-kfreebsd-x86-64.so.1"
+#define GLIBC_DYNAMIC_LINKERX32 "/lib/ld-kfreebsd-x32.so.1"
diff --git a/gcc/config/i386/linux64.h b/gcc/config/i386/linux64.h
index 5d33224..5b0a212 100644
--- a/gcc/config/i386/linux64.h
+++ b/gcc/config/i386/linux64.h
@@ -26,6 +26,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #define GNU_USER_LINK_EMULATION32 "elf_i386"
 #define GNU_USER_LINK_EMULATION64 "elf_x86_64"
+#define GNU_USER_LINK_EMULATIONX32 "elf32_x86_64"
 
 #define GLIBC_DYNAMIC_LINKER32 "/lib/ld-linux.so.2"
 #define GLIBC_DYNAMIC_LINKER64 "/lib64/ld-linux-x86-64.so.2"
+#define GLIBC_DYNAMIC_LINKERX32 "/libx32/ld-linux-x32.so.2"
diff --git a/gcc/config/i386/t-linux-x32 b/gcc/config/i386/t-linux-x32
new file mode 100644
index 0000000..92acf91
--- /dev/null
+++ b/gcc/config/i386/t-linux-x32
@@ -0,0 +1,42 @@
+# Copyright (C) 2011 Free Software Foundation, Inc.
+#
+# This file is part of GCC.
+#
+# GCC 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.
+#
+# GCC 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 GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# On Debian, Ubuntu and other derivative distributions, the 32bit libraries
+# are found in /lib32 and /usr/lib32, /lib64 and /usr/lib64 are symlinks to
+# /lib and /usr/lib, while other distributions install libraries into /lib64
+# and /usr/lib64.  The LSB does not enforce the use of /lib64 and /usr/lib64,
+# it doesn't tell anything about the 32bit libraries on those systems.  Set
+# MULTILIB_OSDIRNAMES according to what is found on the target.
+
+# To support i386, x86-64 and x32 libraries, the directory structrue
+# should be:
+#
+# 	/lib has i386 libraries.
+# 	/lib64 has x86-64 libraries.
+# 	/libx32 has x32 libraries.
+#
+MULTILIB_OPTIONS = m64/m32/mx32
+MULTILIB_DIRNAMES = 64 32 x32
+MULTILIB_OSDIRNAMES = ../lib64 $(if $(wildcard $(shell echo $(SYSTEM_HEADER_DIR))/../../usr/lib32),../lib32,../lib) ../libx32
+
+LIBGCC = stmp-multilib
+INSTALL_LIBGCC = install-multilib
+
+EXTRA_MULTILIB_PARTS=crtbegin.o crtend.o crtbeginS.o crtendS.o \
+		     crtbeginT.o crtprec32.o crtprec64.o crtprec80.o \
+		     crtfastmath.o
diff --git a/gcc/config/linux.h b/gcc/config/linux.h
index fc897b1..dbbeea5 100644
--- a/gcc/config/linux.h
+++ b/gcc/config/linux.h
@@ -77,9 +77,11 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define UCLIBC_DYNAMIC_LINKER "/lib/ld-uClibc.so.0"
 #define UCLIBC_DYNAMIC_LINKER32 "/lib/ld-uClibc.so.0"
 #define UCLIBC_DYNAMIC_LINKER64 "/lib/ld64-uClibc.so.0"
+#define UCLIBC_DYNAMIC_LINKERX32 "/lib/ldx32-uClibc.so.0"
 #define BIONIC_DYNAMIC_LINKER "/system/bin/linker"
 #define BIONIC_DYNAMIC_LINKER32 "/system/bin/linker"
 #define BIONIC_DYNAMIC_LINKER64 "/system/bin/linker64"
+#define BIONIC_DYNAMIC_LINKERX32 "/system/bin/linkerx32"
 
 #define GNU_USER_DYNAMIC_LINKER						\
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER,	\
@@ -90,6 +92,9 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define GNU_USER_DYNAMIC_LINKER64					\
   CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64, \
 			 BIONIC_DYNAMIC_LINKER64)
+#define GNU_USER_DYNAMIC_LINKERX32					\
+  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKERX32, UCLIBC_DYNAMIC_LINKERX32, \
+			 BIONIC_DYNAMIC_LINKERX32)
 
 /* Determine whether the entire c99 runtime
    is present in the runtime library.  */
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 5f3641b..a73f758 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -795,7 +795,7 @@ esac],
 [enable_languages=c])
 
 AC_ARG_WITH(multilib-list,
-[AS_HELP_STRING([--with-multilib-list], [select multilibs (SH only)])],
+[AS_HELP_STRING([--with-multilib-list], [select multilibs (SH and x86-64 only)])],
 :,
 with_multilib_list=default)
 
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 49aac95..a5d266c 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1049,8 +1049,10 @@ sysv, aix.
 @item --with-multilib-list=@var{list}
 @itemx --without-multilib-list
 Specify what multilibs to build.
-Currently only implemented for sh*-*-*.
+Currently only implemented for sh*-*-* and x86-64-*-linux*.
 
+@table @code
+@item sh*-*-*
 @var{list} is a comma separated list of CPU names.  These must be of the
 form @code{sh*} or @code{m*} (in which case they match the compiler option
 for that processor).  The list should not contain any endian options -
@@ -1082,6 +1084,12 @@ only little endian SH4AL:
 --with-multilib-list=sh4al,!mb/m4al
 @end smallexample
 
+@item x86-64-*-linux*
+If @var{list} is @code{x32}, x32 run-time library will be enabled.  By
+default, x32 run-time library is disabled.
+
+@end table
+
 @item --with-endian=@var{endians}
 Specify what endians to use.
 Currently only implemented for sh*-*-*.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1fc4038..fd6711c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -610,7 +610,7 @@ Objective-C and Objective-C++ Dialects}.
 -mpc32 -mpc64 -mpc80 -mstackrealign @gol
 -momit-leaf-frame-pointer  -mno-red-zone -mno-tls-direct-seg-refs @gol
 -mcmodel=@var{code-model} -mabi=@var{name} @gol
--m32  -m64 -mlarge-data-threshold=@var{num} @gol
+-m32 -m64 -mx32 -mlarge-data-threshold=@var{num} @gol
 -msse2avx -mfentry -m8bit-idiv @gol
 -mavx256-split-unaligned-load -mavx256-split-unaligned-store}
 
@@ -12851,15 +12851,19 @@ on AMD x86-64 processors in 64-bit environments.
 @table @gcctabopt
 @item -m32
 @itemx -m64
+@itemx -mx32
 @opindex m32
 @opindex m64
+@opindex mx32
 Generate code for a 32-bit or 64-bit environment.
-The 32-bit environment sets int, long and pointer to 32 bits and
+The @option{-m32} option sets int, long and pointer to 32 bits and
 generates code that runs on any i386 system.
-The 64-bit environment sets int to 32 bits and long and pointer
-to 64 bits and generates code for AMD's x86-64 architecture. For
-darwin only the -m64 option turns off the @option{-fno-pic} and
-@option{-mdynamic-no-pic} options.
+The @option{-m64} option sets int to 32 bits and long and pointer
+to 64 bits and generates code for AMD's x86-64 architecture.
+The @option{-mx32} option sets int, long and pointer to 32 bits and
+generates code for AMD's x86-64 architecture.
+For darwin only the @option{-m64} option turns off the @option{-fno-pic}
+and @option{-mdynamic-no-pic} options.
 
 @item -mno-red-zone
 @opindex mno-red-zone