6 files changed, 98 insertions, 1 deletions
diff --git a/libgcc/config.host b/libgcc/config.host
index 6afe8e5..694e3e9 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -554,7 +554,7 @@ arm*-*-eabi* | arm*-*-symbianelf* | arm*-*-rtems*)
 	tm_file="$tm_file arm/bpabi-lib.h"
 	case ${host} in
 	arm*-*-eabi* | arm*-*-rtems*)
-	  tmake_file="${tmake_file} arm/t-bpabi t-crtfm"
+	  tmake_file="${tmake_file} arm/t-bpabi arm/t-sync t-crtfm"
 	  extra_parts="crtbegin.o crtend.o crti.o crtn.o"
 	  ;;
 	arm*-*-symbianelf*)
diff --git a/libgcc/config/arm/lib1funcs.S b/libgcc/config/arm/lib1funcs.S
index d02a57c..7888786 100644
--- a/libgcc/config/arm/lib1funcs.S
+++ b/libgcc/config/arm/lib1funcs.S
@@ -2147,6 +2147,78 @@ LSYM(Lchange_\register):
 	SIZE (__gnu_thumb1_case_uhi)
 #endif
 
+#ifdef L_sync_none
+	/* Null implementation of __sync_synchronize, for use when
+	   it is known that the system is single threaded.  */
+	.text
+	.align 0
+	FUNC_START sync_synchronize_none
+	bx	lr
+	FUNC_END sync_synchronize_none
+#endif
+
+#ifdef L_sync_dmb
+	/* Full memory barrier using DMB.  Requires Armv7 (all profiles)
+	or armv6-m, or later.  */
+	.text
+	.align 0
+#if __ARM_ARCH_PROFILE == 'M'
+	.arch armv6-m
+#else
+	.arch armv7-a
+#endif
+	FUNC_START sync_synchronize_dmb
+	/* M-profile devices only support SY as the synchronization level,
+	   but that's probably what we want here anyway.  */
+	dmb
+	RET
+	FUNC_END sync_synchronize_dmb
+#endif
+
+#ifdef L_sync_cp15dmb
+#ifndef NOT_ISA_TARGET_32BIT
+	/* Implementation of DMB using CP15 operations.  This was first
+	   defined in Armv6, but deprecated in Armv7 and can give
+	   sub-optimal performance.  */
+	.text
+	.align 0
+	ARM_FUNC_START sync_synchronize_cp15dmb
+	mcr	p15, 0, r0, c7, c10, 5
+	RET
+	FUNC_END sync_synchronize_cp15dmb
+#endif
+#endif
+
+#ifdef L_sync_synchronize
+	/* Generic version of the synchronization primitive.  If we know
+	   that DMB exists, then use it.  Otherwise, arrange for a link
+	   time warning explaining how to pick a suitable alternative.
+	   We choose not to use CP15DMB because it is performance
+	   deprecated.  We only define this function if generating
+	   ELF binaries as otherwise we can't rely on the warning being
+	   generated.  */
+
+#ifdef __ELF__
+	.text
+	.align 0
+	FUNC_START sync_synchronize
+#if __ARM_ARCH >= 7 || __ARM_ARCH_PROFILE == 'M'
+	dmb
+#endif
+	RET
+	FUNC_END sync_synchronize
+#if !(__ARM_ARCH >= 7 || __ARM_ARCH_PROFILE == 'M')
+	.section .gnu.warning.__sync_synchronize
+	.align 0
+	.ascii "This implementation of __sync_synchronize is a stub with "
+	.ascii "no effect.  Relink with\n"
+	.ascii "  -specs=sync-{none,dmb,cp15dmb}.specs\n"
+	.ascii "to specify exactly which barrier format to use and avoid "
+	.ascii "this warning.\n\0"
+#endif
+#endif
+#endif
+
 #ifdef L_thumb1_case_si
 	
 	.text
diff --git a/libgcc/config/arm/sync-cp15dmb.specs b/libgcc/config/arm/sync-cp15dmb.specs
new file mode 100644
index 0000000..0bb64b9
--- /dev/null
+++ b/libgcc/config/arm/sync-cp15dmb.specs
@@ -0,0 +1,4 @@
+%rename link sync_sync_link
+
+*link:
+--defsym=__sync_synchronize=__sync_synchronize_cp15dmb %(sync_sync_link)
diff --git a/libgcc/config/arm/sync-dmb.specs b/libgcc/config/arm/sync-dmb.specs
new file mode 100644
index 0000000..13e59bd
--- /dev/null
+++ b/libgcc/config/arm/sync-dmb.specs
@@ -0,0 +1,4 @@
+%rename link sync_sync_link
+
+*link:
+--defsym=__sync_synchronize=__sync_synchronize_dmb %(sync_sync_link)
diff --git a/libgcc/config/arm/sync-none.specs b/libgcc/config/arm/sync-none.specs
new file mode 100644
index 0000000..0aa4960
--- /dev/null
+++ b/libgcc/config/arm/sync-none.specs
@@ -0,0 +1,4 @@
+%rename link sync_sync_link
+
+*link:
+--defsym=__sync_synchronize=__sync_synchronize_none %(sync_sync_link)
diff --git a/libgcc/config/arm/t-sync b/libgcc/config/arm/t-sync
new file mode 100644
index 0000000..5fd050e
--- /dev/null
+++ b/libgcc/config/arm/t-sync
@@ -0,0 +1,13 @@
+LIB1ASMFUNCS += _sync_none _sync_dmb _sync_cp15dmb _sync_synchronize
+
+EXTRA_PARTS += sync-none.specs sync-dmb.specs sync-cp15dmb.specs
+
+sync-none.specs: $(srcdir)/config/arm/sync-none.specs
+	cp $< .
+
+sync-dmb.specs: $(srcdir)/config/arm/sync-dmb.specs
+	cp $< .
+
+sync-cp15dmb.specs: $(srcdir)/config/arm/sync-cp15dmb.specs
+	cp $< .
+