RFA: Allowing __sync_* functions to be added to libgcc

[Richard Sandiford <rdsandiford at googlemail dot com>]

Following on from:

    http://gcc.gnu.org/ml/gcc-patches/2008-06/msg01693.html

MIPS16 code relies on external routines for the __sync_* builtins.
We can implement them using simple wrappers like:

  static TYPE
  sync_fetch_and_add_N (TYPE *ptr, TYPE value)
  {
    return __sync_fetch_and_add (ptr, value);
  }
  typeof (sync_fetch_and_add_N) __sync_fetch_and_add_N
    __attribute__((alias ("sync_fetch_and_add_N")));

provided that we compile the code with -mno-mips16.  (We could use
attributes instead, but compiling with -mno-mips16 is simpler.)

This patch adds optional libgcc suppport for this.  There are two
new macros:

  - LIBGCC_SYNC: set to "yes" to enable the routines.
  - LIBGCC_SYNC_FLAGS: extra options to pass when compiling them.

Note that setting LIBGCC_SYNC to "yes" is a no-op when
$(LIBGCC_SYNC_FLAGS) does not enable __sync_* support.
This is important for normal mips-elf, because MIPS I doesn't
have LL, SC and SYNC instructions.  (However, mips-elf configured
with --with-arch=mips2 or --with-llsc _will_ have these routines.)

At the moment, no target supports both MIPS16 and DSOs, but I'm going to
post a patch in a few days to add o32 GNU/Linux support.  I've therefore
included symbol versions for the new routines.

Tested on mipsisa64-elfoabi, x86_64-linux-gnu and the to-be-submitted
MIPS16-enabled mips64-linux-gnu configuration.  OK to install?

Richard


gcc/
	* Makefile.in (libgcc.mvars): Add LIBGCC_SYNC and LIBGCC_SYNC_CFLAGS.
	* libgcc-std.ver (GCC_4.4.0): New version, inherited from GCC_4.3.0.
	Add synchronization functions.
	* config/sync.c: New file.
	* config/mips/t-libgcc-mips16 (LIBGCC_SYNC): Define.
	(LIBGCC_SYNC_CFLAGS): Likewise.

libgcc/
	* Makefile.in: Add support for __sync_* libgcc functions.

Index: gcc/gcc/Makefile.in
===================================================================
--- gcc.orig/gcc/Makefile.in	2008-06-26 21:50:49.000000000 +0100
+++ gcc/gcc/Makefile.in	2008-06-26 21:51:04.000000000 +0100
@@ -1661,6 +1661,8 @@ libgcc.mvars: config.status Makefile $(L
 	echo SHLIB_MAPFILES = '$(call srcdirify,$(SHLIB_MAPFILES))' >> tmp-libgcc.mvars
 	echo SHLIB_NM_FLAGS = '$(SHLIB_NM_FLAGS)' >> tmp-libgcc.mvars
 	echo LIBGCC2_CFLAGS = '$(LIBGCC2_CFLAGS)' >> tmp-libgcc.mvars
+	echo LIBGCC_SYNC = '$(LIBGCC_SYNC)' >> tmp-libgcc.mvars
+	echo LIBGCC_SYNC_CFLAGS = '$(LIBGCC_SYNC_CFLAGS)' >> tmp-libgcc.mvars
 	echo CRTSTUFF_CFLAGS = '$(CRTSTUFF_CFLAGS)' >> tmp-libgcc.mvars
 	echo CRTSTUFF_T_CFLAGS = '$(CRTSTUFF_T_CFLAGS)' >> tmp-libgcc.mvars
 	echo CRTSTUFF_T_CFLAGS_S = '$(CRTSTUFF_T_CFLAGS_S)' >> tmp-libgcc.mvars
Index: gcc/gcc/config/mips/t-libgcc-mips16
===================================================================
--- gcc.orig/gcc/config/mips/t-libgcc-mips16	2008-06-26 21:50:49.000000000 +0100
+++ gcc/gcc/config/mips/t-libgcc-mips16	2008-06-26 21:55:15.000000000 +0100
@@ -19,3 +19,6 @@ LIB1ASMFUNCS = _m16addsf3 _m16subsf3 _m1
 	_m16stubsc9 _m16stubsc10 \
 	_m16stubdc0 _m16stubdc1 _m16stubdc2 _m16stubdc5 _m16stubdc6 \
 	_m16stubdc9 _m16stubdc10
+
+LIBGCC_SYNC = yes
+LIBGCC_SYNC_CFLAGS = -mno-mips16
Index: gcc/gcc/libgcc-std.ver
===================================================================
--- gcc.orig/gcc/libgcc-std.ver	2008-06-26 21:50:49.000000000 +0100
+++ gcc/gcc/libgcc-std.ver	2008-06-26 21:51:04.000000000 +0100
@@ -1800,3 +1800,88 @@ GCC_4.3.0 {
   __satfractunstiuda
   __satfractunstiuta
 }
+
+%inherit GCC_4.4.0 GCC_4.3.0
+GCC_4.4.0 {
+  __sync_fetch_and_add_1
+  __sync_fetch_and_sub_1
+  __sync_fetch_and_or_1
+  __sync_fetch_and_and_1
+  __sync_fetch_and_xor_1
+  __sync_fetch_and_nand_1
+  __sync_add_and_fetch_1
+  __sync_sub_and_fetch_1
+  __sync_or_and_fetch_1
+  __sync_and_and_fetch_1
+  __sync_xor_and_fetch_1
+  __sync_nand_and_fetch_1
+  __sync_bool_compare_and_swap_1
+  __sync_val_compare_and_swap_1
+  __sync_lock_test_and_set_1
+
+  __sync_fetch_and_add_2
+  __sync_fetch_and_sub_2
+  __sync_fetch_and_or_2
+  __sync_fetch_and_and_2
+  __sync_fetch_and_xor_2
+  __sync_fetch_and_nand_2
+  __sync_add_and_fetch_2
+  __sync_sub_and_fetch_2
+  __sync_or_and_fetch_2
+  __sync_and_and_fetch_2
+  __sync_xor_and_fetch_2
+  __sync_nand_and_fetch_2
+  __sync_bool_compare_and_swap_2
+  __sync_val_compare_and_swap_2
+  __sync_lock_test_and_set_2
+
+  __sync_fetch_and_add_4
+  __sync_fetch_and_sub_4
+  __sync_fetch_and_or_4
+  __sync_fetch_and_and_4
+  __sync_fetch_and_xor_4
+  __sync_fetch_and_nand_4
+  __sync_add_and_fetch_4
+  __sync_sub_and_fetch_4
+  __sync_or_and_fetch_4
+  __sync_and_and_fetch_4
+  __sync_xor_and_fetch_4
+  __sync_nand_and_fetch_4
+  __sync_bool_compare_and_swap_4
+  __sync_val_compare_and_swap_4
+  __sync_lock_test_and_set_4
+
+  __sync_fetch_and_add_8
+  __sync_fetch_and_sub_8
+  __sync_fetch_and_or_8
+  __sync_fetch_and_and_8
+  __sync_fetch_and_xor_8
+  __sync_fetch_and_nand_8
+  __sync_add_and_fetch_8
+  __sync_sub_and_fetch_8
+  __sync_or_and_fetch_8
+  __sync_and_and_fetch_8
+  __sync_xor_and_fetch_8
+  __sync_nand_and_fetch_8
+  __sync_bool_compare_and_swap_8
+  __sync_val_compare_and_swap_8
+  __sync_lock_test_and_set_8
+
+  __sync_fetch_and_add_16
+  __sync_fetch_and_sub_16
+  __sync_fetch_and_or_16
+  __sync_fetch_and_and_16
+  __sync_fetch_and_xor_16
+  __sync_fetch_and_nand_16
+  __sync_add_and_fetch_16
+  __sync_sub_and_fetch_16
+  __sync_or_and_fetch_16
+  __sync_and_and_fetch_16
+  __sync_xor_and_fetch_16
+  __sync_nand_and_fetch_16
+  __sync_bool_compare_and_swap_16
+  __sync_val_compare_and_swap_16
+  __sync_lock_test_and_set_16
+
+  __sync_synchronize
+}
Index: gcc/libgcc/Makefile.in
===================================================================
--- gcc.orig/libgcc/Makefile.in	2008-06-26 21:50:49.000000000 +0100
+++ gcc/libgcc/Makefile.in	2008-06-26 21:51:04.000000000 +0100
@@ -577,6 +577,54 @@ endif
 
 endif
 
+ifeq ($(LIBGCC_SYNC),yes)
+libgcc-sync-size-funcs := $(foreach op, add sub or and xor nand, \
+			    sync_fetch_and_$(op) \
+			    sync_$(op)_and_fetch) \
+			  sync_bool_compare_and_swap \
+			  sync_val_compare_and_swap \
+			  sync_lock_test_and_set
+
+libgcc-sync-size-funcs := $(foreach prefix, $(libgcc-sync-size-funcs), \
+			    $(foreach suffix, 1 2 4 8 16, \
+			      $(prefix)_$(suffix)))
+
+libgcc-sync-size-funcs-o = $(patsubst %,%$(objext),$(libgcc-sync-size-funcs))
+$(libgcc-sync-size-funcs-o): %$(objext): $(gcc_srcdir)/config/sync.c
+	$(gcc_compile) $(LIBGCC_SYNC_CFLAGS) \
+	  -DFN=`echo "$*" | sed 's/_[^_]*$$//'` \
+	  -DSIZE=`echo "$*" | sed 's/.*_//'` \
+	  -c $(gcc_srcdir)/config/sync.c $(vis_hide)
+libgcc-objects += $(libgcc-sync-size-funcs-o)
+
+libgcc-sync-funcs := sync_synchronize
+
+libgcc-sync-funcs-o = $(patsubst %,%$(objext),$(libgcc-sync-funcs))
+$(libgcc-sync-funcs-o): %$(objext): $(gcc_srcdir)/config/sync.c
+	$(gcc_compile) $(LIBGCC_SYNC_CFLAGS) \
+	  -DL$* \
+	  -c $(gcc_srcdir)/config/sync.c $(vis_hide)
+libgcc-objects += $(libgcc-sync-funcs-o)
+
+ifeq ($(enable_shared),yes)
+libgcc-sync-size-funcs-s-o = $(patsubst %,%_s$(objext), \
+			       $(libgcc-sync-size-funcs))
+$(libgcc-sync-size-funcs-s-o): %_s$(objext): $(gcc_srcdir)/config/sync.c
+	$(gcc_s_compile) $(LIBGCC_SYNC_CFLAGS) \
+	  -DFN=`echo "$*" | sed 's/_[^_]*$$//'` \
+	  -DSIZE=`echo "$*" | sed 's/.*_//'` \
+	  -c $(gcc_srcdir)/config/sync.c
+libgcc-s-objects += $(libgcc-sync-size-funcs-s-o)
+
+libgcc-sync-funcs-s-o = $(patsubst %,%_s$(objext),$(libgcc-sync-funcs))
+$(libgcc-sync-funcs-s-o): %_s$(objext): $(gcc_srcdir)/config/sync.c
+	$(gcc_s_compile) $(LIBGCC_SYNC_CFLAGS) \
+	  -DL$*	\
+	  -c $(gcc_srcdir)/config/sync.c
+libgcc-s-objects += $(libgcc-sync-funcs-s-o)
+endif
+endif
+
 # Build fixed-point support.
 ifeq ($(fixed_point),yes)
 
Index: gcc/gcc/config/sync.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/config/sync.c	2008-06-26 21:52:20.000000000 +0100
@@ -0,0 +1,185 @@
+/* Out-of-line libgcc versions of __sync_* builtins.  */
+/* Copyright (C) 2008  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 2, or (at your option) any later
+version.
+
+In addition to the permissions in the GNU General Public License, the
+Free Software Foundation gives you unlimited permission to link the
+compiled version of this file into combinations with other programs,
+and to distribute those combinations without any restriction coming
+from the use of this file.  (The General Public License restrictions
+do apply in other respects; for example, they cover modification of
+the file, and distribution when not linked into a combine
+executable.)
+
+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 COPYING.  If not, write to the Free
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
+
+/* This file is used by targets whose makefiles define LIBGCC_SYNC
+   to "yes".  It is compiled with LIBGCC_SYNC_CFLAGS and provides
+   out-of-line versions of all relevant __sync_* primitives.
+
+   These routines are intended for targets like MIPS that have two
+   ISA encodings (the "normal" ISA and the MIPS16 ISA).  The normal
+   ISA provides full synchronization capabilities but the MIPS16 ISA
+   has no encoding for them.  MIPS16 code must therefore call external
+   non-MIPS16 implementations of the __sync_* routines.
+
+   The file is compiled once for each routine.  The following routines
+   are selected by defining a macro called L<name>:
+
+       __sync_synchronize
+
+   The following __foo_N routines are selected by defining FN=foo
+   and SIZE=N:
+
+       __sync_fetch_and_add_N
+       __sync_fetch_and_sub_N
+       __sync_fetch_and_or_N
+       __sync_fetch_and_and_N
+       __sync_fetch_and_xor_N
+       __sync_fetch_and_nand_N
+       __sync_add_and_fetch_N
+       __sync_sub_and_fetch_N
+       __sync_or_and_fetch_N
+       __sync_and_and_fetch_N
+       __sync_xor_and_fetch_N
+       __sync_nand_and_fetch_N
+       __sync_bool_compare_and_swap_N
+       __sync_val_compare_and_swap_N
+       __sync_lock_test_and_set_N
+
+   SIZE can be 1, 2, 4, 8 or 16.  __foo_N is omitted if the target does
+   not provide __sync_compare_and_swap_N.
+
+   Note that __sync_lock_release does not fall back on external
+   __sync_lock_release_N functions.  The default implementation
+   of __sync_lock_release is a call to __sync_synchronize followed
+   by a store of zero, so we don't need separate library functions
+   for it.  */
+
+#if defined FN
+
+/* Define macros for each __sync_* function type.  Each macro defines a
+   local function called <NAME>_<UNITS> that acts like __<NAME>_<UNITS>.
+   TYPE is a type that has UNITS bytes.  */
+
+#define DEFINE_V_PV(NAME, UNITS, TYPE)					\
+  static TYPE								\
+  NAME##_##UNITS (TYPE *ptr, TYPE value)				\
+  {									\
+    return __##NAME (ptr, value);					\
+  }
+
+#define DEFINE_V_PVV(NAME, UNITS, TYPE)				\
+  static TYPE								\
+  NAME##_##UNITS (TYPE *ptr, TYPE value1, TYPE value2)			\
+  {									\
+    return __##NAME (ptr, value1, value2);				\
+  }
+
+#define DEFINE_BOOL_PVV(NAME, UNITS, TYPE)				\
+  static _Bool								\
+  NAME##_##UNITS (TYPE *ptr, TYPE value1, TYPE value2)			\
+  {									\
+    return __##NAME (ptr, value1, value2);				\
+  }
+
+/* Map function names to the appropriate DEFINE_* macro.  */
+
+#define local_sync_fetch_and_add DEFINE_V_PV
+#define local_sync_fetch_and_sub DEFINE_V_PV
+#define local_sync_fetch_and_or DEFINE_V_PV
+#define local_sync_fetch_and_and DEFINE_V_PV
+#define local_sync_fetch_and_xor DEFINE_V_PV
+#define local_sync_fetch_and_nand DEFINE_V_PV
+
+#define local_sync_add_and_fetch DEFINE_V_PV
+#define local_sync_sub_and_fetch DEFINE_V_PV
+#define local_sync_or_and_fetch DEFINE_V_PV
+#define local_sync_and_and_fetch DEFINE_V_PV
+#define local_sync_xor_and_fetch DEFINE_V_PV
+#define local_sync_nand_and_fetch DEFINE_V_PV
+
+#define local_sync_bool_compare_and_swap DEFINE_BOOL_PVV
+#define local_sync_val_compare_and_swap DEFINE_V_PVV
+
+#define local_sync_lock_test_and_set DEFINE_V_PV
+
+/* Define the function __<NAME>_<UNITS>, given that TYPE is a type with
+   UNITS bytes.  */
+#define DEFINE1(NAME, UNITS, TYPE) \
+  static int unused[sizeof (TYPE) == UNITS ? 1 : -1]	\
+    __attribute__((unused));				\
+  local_##NAME (NAME, UNITS, TYPE);			\
+  typeof (NAME##_##UNITS) __##NAME##_##UNITS		\
+    __attribute__((alias (#NAME "_" #UNITS)));
+
+/* As above, but performing macro expansion on the arguments.  */
+#define DEFINE(NAME, UNITS, TYPE) DEFINE1 (NAME, UNITS, TYPE)
+
+/* Find an appropriate type TYPE for SIZE and invoke DEFINE (FN, SIZE, TYPE).
+
+   The types chosen here may be incorrect for some targets.
+   For example, targets with 16-byte atomicity support might not
+   support OImode.  We would need some kind of target-specific
+   override if that becomes a problem.  */
+
+#if SIZE == 1 && __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1
+
+typedef unsigned int UQItype __attribute__((mode (QI)));
+DEFINE (FN, 1, UQItype)
+
+#elif SIZE == 2 && __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2
+
+typedef unsigned int UHItype __attribute__((mode (HI)));
+DEFINE (FN, 2, UHItype)
+
+#elif SIZE == 4 && __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
+
+typedef unsigned int USItype __attribute__((mode (SI)));
+DEFINE (FN, 4, USItype)
+
+#elif SIZE == 8 && __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8
+
+typedef unsigned int UDItype __attribute__((mode (DI)));
+DEFINE (FN, 8, UDItype)
+
+#elif SIZE == 16 && __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16
+
+typedef unsigned int UOItype __attribute__((mode (OI)));
+DEFINE (FN, 8, UOItype)
+
+#endif
+
+#elif __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 \
+      || __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 \
+      || __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 \
+      || __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 \
+      || __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16
+
+#if defined Lsync_synchronize
+
+static void
+sync_synchronize (void)
+{
+  __sync_synchronize ();
+}
+typeof (sync_synchronize) __sync_synchronize \
+  __attribute__((alias ("sync_synchronize")));
+
+#endif
+
+#endif