Unbreak <stdatomic.h> on ARM + Clang.

Clang only supports atomic operations for ARMv6. For non-ARMv6, we still
need to emit these functions.

Clang's prototype for these functions slightly differs, as it is truly
based on GCC's documentation. It requires the use of signed types, but
also requires varargs. Still, we are not allowed to simply implement
this function directly. Cleverly work around this by implementing it
under a different name and using __strong_reference().

lib/libcompiler_rt/Makefile

@@ -156,9 +156,8 @@ SRCF+=	divsi3 \
 	umodsi3
 .endif
 
-# FreeBSD-specific atomic intrinsics. Clang provides them as a builtin.
-.if (${MACHINE_CPUARCH} == "arm" && ${COMPILER_TYPE} != "clang") || \
-    ${MACHINE_CPUARCH} == "mips"
+# FreeBSD-specific atomic intrinsics.
+.if ${MACHINE_CPUARCH} == "arm" || ${MACHINE_CPUARCH} == "mips"
 SRCF+=	__sync_fetch_and_add_4 \
 	__sync_fetch_and_and_4 \
 	__sync_fetch_and_or_4 \

lib/libcompiler_rt/__sync_fetch_and_add_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_add_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	FETCHADD(x, y)	atomic_fetchadd_32(x, y)
 
 #include "__sync_fetch_and_op_n.h"

lib/libcompiler_rt/__sync_fetch_and_add_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_add_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	FETCHADD(x, y)	atomic_fetchadd_64(x, y)
 
 #include "__sync_fetch_and_op_n.h"

lib/libcompiler_rt/__sync_fetch_and_and_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_and_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	CMPSET		atomic_cmpset_32
 #define	EXPRESSION	t & value
 

lib/libcompiler_rt/__sync_fetch_and_and_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_and_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	CMPSET		atomic_cmpset_64
 #define	EXPRESSION	t & value
 

lib/libcompiler_rt/__sync_fetch_and_op_n.h

@@ -30,8 +30,13 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <machine/atomic.h>
 
+#if defined __clang__
+static TYPE
+atomic_func(volatile TYPE *ptr, TYPE value, ...)
+#else
 TYPE
 NAME(volatile TYPE *ptr, TYPE value)
+#endif
 {
 	TYPE t;
 
@@ -45,3 +50,7 @@ NAME(volatile TYPE *ptr, TYPE value)
 
 	return (t);
 }
+
+#ifdef __clang__
+__strong_reference(atomic_func, NAME);
+#endif

lib/libcompiler_rt/__sync_fetch_and_or_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_or_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	CMPSET		atomic_cmpset_32
 #define	EXPRESSION	t | value
 

lib/libcompiler_rt/__sync_fetch_and_or_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_or_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	CMPSET		atomic_cmpset_64
 #define	EXPRESSION	t | value
 

lib/libcompiler_rt/__sync_fetch_and_sub_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_sub_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	FETCHADD(x, y)	atomic_fetchadd_32(x, -(y))
 
 #include "__sync_fetch_and_op_n.h"

lib/libcompiler_rt/__sync_fetch_and_sub_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_sub_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	FETCHADD(x, y)	atomic_fetchadd_64(x, -(y))
 
 #include "__sync_fetch_and_op_n.h"

lib/libcompiler_rt/__sync_fetch_and_xor_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_xor_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	CMPSET		atomic_cmpset_32
 #define	EXPRESSION	t ^ value
 

lib/libcompiler_rt/__sync_fetch_and_xor_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_fetch_and_xor_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	CMPSET		atomic_cmpset_64
 #define	EXPRESSION	t ^ value
 

lib/libcompiler_rt/__sync_lock_test_and_set_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_lock_test_and_set_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	CMPSET		atomic_cmpset_32
 #define	EXPRESSION	value
 

lib/libcompiler_rt/__sync_lock_test_and_set_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_lock_test_and_set_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	CMPSET		atomic_cmpset_64
 #define	EXPRESSION	value
 

lib/libcompiler_rt/__sync_val_compare_and_swap_4.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_val_compare_and_swap_4
-#define	TYPE		uint32_t
+#define	TYPE		int32_t
 #define	CMPSET		atomic_cmpset_32
 
 #include "__sync_val_compare_and_swap_n.h"

lib/libcompiler_rt/__sync_val_compare_and_swap_8.c

@@ -1,6 +1,6 @@
 /* $FreeBSD$ */
 #define	NAME		__sync_val_compare_and_swap_8
-#define	TYPE		uint64_t
+#define	TYPE		int64_t
 #define	CMPSET		atomic_cmpset_64
 
 #include "__sync_val_compare_and_swap_n.h"

lib/libcompiler_rt/__sync_val_compare_and_swap_n.h

@@ -30,8 +30,13 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <machine/atomic.h>
 
+#if defined __clang__
+static TYPE
+atomic_func(volatile TYPE *ptr, TYPE oldval, TYPE newval, ...)
+#else
 TYPE
 NAME(volatile TYPE *ptr, TYPE oldval, TYPE newval)
+#endif
 {
 	TYPE t;
 
@@ -43,3 +48,7 @@ NAME(volatile TYPE *ptr, TYPE oldval, TYPE newval)
 
 	return (oldval);
 }
+
+#ifdef __clang__
+__strong_reference(atomic_func, NAME);
+#endif