[Patch ARM] Provide stub function for __sync_synchronize

[Ramana Radhakrishnan]

Hi,

	A recent change to g++ means that we now put out
calls to __sync_synchronize for C++ guard variables for
versions of the architecture that do not have a barrier
instruction. Instead of ignoring the problem in the compiler
and working around it by providing a stub in libgcc, provide a
weak definition here in order for testing to succeed but to highlight
this for users provide a link time warning when this is used.

Additionally libgfortran now pulls in libbacktrace which expects
to be able to use atomic accesses where required. This creates
problems when testing in bare-metal configurations. 

This means though that developers and testers for arm-none-eabi
will have to add something to prune additional output in their
site.exp's with an additional implementation of prune_warnings
to prune the warnings but this is more prudent than
just putting out silent calls to __sync_synchronize.

Tested this for arm-none-eabi with --with-multilib-list=aprofile
with suitable multilibs.

Thoughts ? 

Ok ?

Ramana

<DATE>  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>

	* libc/machine/arm/sync_synchronize.c: New file.
	* libc/machine/arm/Makefile.am: Add sync_synchronize.c
	* libc/machine/arm/Makefile.in: Regenerate.
-------------- next part --------------
commit a839594943b59b6ba81d1f37f7684f156598f2d1
Author: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Date:   Tue Sep 8 09:48:37 2015 +0100

    [Patch ARM] Provide __sync_synchronize stub.
    
    A recent change to g++ means that we now put out
    calls to __sync_synchronize for C++ guard variables for
    versions of the architecture that do not have a barrier
    instruction. Instead of ignoring the problem in the compiler
    and working around it by providing a stub in libgcc, provide a
    weak definition here in order for testing to succeed but for
    users to provide their own definition of the same.
    
    Additionally libgfortran now pulls in libbacktrace which expects
    to be able to use atomic accesses where required. This creates
    problems when testing in bare-metal configurations.
    
    <DATE>  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
    
    	* libc/machine/arm/sync_synchronize.c: New file.
    	* libc/machine/arm/Makefile.am: Add sync_synchronize.c
    	* libc/machine/arm/Makefile.in: Regenerate.

diff --git a/newlib/libc/machine/arm/Makefile.am b/newlib/libc/machine/arm/Makefile.am
index 55bc0a7..2f4b2e2 100644
--- a/newlib/libc/machine/arm/Makefile.am
+++ b/newlib/libc/machine/arm/Makefile.am
@@ -51,7 +51,8 @@ lib_a_SOURCES = setjmp.S access.c strcmp.S strcpy.c \
 	        $(MEMCPY_SRC) $(MEMCHR_SRC) $(STRLEN_SRC) \
 		strlen-armv7.S aeabi_memcpy.c aeabi_memcpy-armv7a.S \
 		aeabi_memmove.c aeabi_memmove-soft.S \
-		aeabi_memset.c aeabi_memset-soft.S aeabi_memclr.c
+		aeabi_memset.c aeabi_memset-soft.S aeabi_memclr.c \
+		sync_synchronize.c
 
 lib_a_CCASFLAGS=$(AM_CCASFLAGS)
 lib_a_CFLAGS = $(AM_CFLAGS)
diff --git a/newlib/libc/machine/arm/Makefile.in b/newlib/libc/machine/arm/Makefile.in
index 7a3506e..364b798 100644
--- a/newlib/libc/machine/arm/Makefile.in
+++ b/newlib/libc/machine/arm/Makefile.in
@@ -89,7 +89,7 @@ am_lib_a_OBJECTS = lib_a-setjmp.$(OBJEXT) lib_a-access.$(OBJEXT) \
 	lib_a-aeabi_memmove.$(OBJEXT) \
 	lib_a-aeabi_memmove-soft.$(OBJEXT) \
 	lib_a-aeabi_memset.$(OBJEXT) lib_a-aeabi_memset-soft.$(OBJEXT) \
-	lib_a-aeabi_memclr.$(OBJEXT)
+	lib_a-aeabi_memclr.$(OBJEXT) lib_a-sync_synchronize.$(OBJEXT)
 lib_a_OBJECTS = $(am_lib_a_OBJECTS)
 DEFAULT_INCLUDES = -I.@am__isrc@
 depcomp =
@@ -238,7 +238,8 @@ lib_a_SOURCES = setjmp.S access.c strcmp.S strcpy.c \
 	        $(MEMCPY_SRC) $(MEMCHR_SRC) $(STRLEN_SRC) \
 		strlen-armv7.S aeabi_memcpy.c aeabi_memcpy-armv7a.S \
 		aeabi_memmove.c aeabi_memmove-soft.S \
-		aeabi_memset.c aeabi_memset-soft.S aeabi_memclr.c
+		aeabi_memset.c aeabi_memset-soft.S aeabi_memclr.c \
+		sync_synchronize.c
 
 lib_a_CCASFLAGS = $(AM_CCASFLAGS)
 lib_a_CFLAGS = $(AM_CFLAGS)
@@ -410,6 +411,12 @@ lib_a-aeabi_memclr.o: aeabi_memclr.c
 lib_a-aeabi_memclr.obj: aeabi_memclr.c
 	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-aeabi_memclr.obj `if test -f 'aeabi_memclr.c'; then $(CYGPATH_W) 'aeabi_memclr.c'; else $(CYGPATH_W) '$(srcdir)/aeabi_memclr.c'; fi`
 
+lib_a-sync_synchronize.o: sync_synchronize.c
+	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-sync_synchronize.o `test -f 'sync_synchronize.c' || echo '$(srcdir)/'`sync_synchronize.c
+
+lib_a-sync_synchronize.obj: sync_synchronize.c
+	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-sync_synchronize.obj `if test -f 'sync_synchronize.c'; then $(CYGPATH_W) 'sync_synchronize.c'; else $(CYGPATH_W) '$(srcdir)/sync_synchronize.c'; fi`
+
 ID: $(HEADERS) $(SOURCES) $(LISP) $(TAGS_FILES)
 	list='$(SOURCES) $(HEADERS) $(LISP) $(TAGS_FILES)'; \
 	unique=`for i in $$list; do \
diff --git a/newlib/libc/machine/arm/sync_synchronize.c b/newlib/libc/machine/arm/sync_synchronize.c
new file mode 100644
index 0000000..7695ebc
--- /dev/null
+++ b/newlib/libc/machine/arm/sync_synchronize.c
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2015 ARM Ltd
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the company may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* This is a fall-back definition only to handle legacy architectures
+   which do not have any expectation of providing multi-core support.
+   This function stub is provided for testsuites to work without
+   issues and for linking to complete, but if a platform requires any
+   kind of multi-threading support it is expected that the platform
+   will override the implementation of this barrier intrinsic.  */
+
+#include <sys/cdefs.h>
+void __attribute__((weak))
+__sync_synchronize (void)
+{
+  __warn_references (__sync_synchronize,
+		     "Warning:Provide a suitable definition for __sync_synchronize");
+  return;
+}