Add byteorder.S for ARM64

Change-Id: I346e83683ad2318948914c5027123f84d4038451
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3737
Reviewed-by: Fredrik Holmqvist <fredrik.holmqvist@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

src/system/kernel/lib/arch/arm64/Jamfile

@@ -9,6 +9,7 @@ SEARCH_SOURCE += [ FDirName $(librootSources) os arch $(TARGET_ARCH) ] ;
 SEARCH_SOURCE += [ FDirName $(librootSources) os arch generic ] ;
 
 KernelMergeObject kernel_os_arch_$(TARGET_ARCH).o :
+	byteorder.S
 	generic_atomic.cpp
 	generic_system_time_nsecs.cpp
 
@@ -24,7 +25,7 @@ KernelMergeObject kernel_lib_posix_arch_$(TARGET_ARCH).o :
 	sigsetjmp.S
 	kernel_longjmp_return.c
 	kernel_setjmp_save_sigs.c
-	
+
 	arch_string.S
 	memset.c
 	memcpy.c

src/system/libroot/os/arch/arm64/Jamfile

@@ -13,11 +13,12 @@ for architectureObject in [ MultiArchSubDirSetup arm64 ] {
 		SEARCH_SOURCE += [ FDirName $(SUBDIR) $(DOTDOT) generic ] ;
 
 		MergeObject <$(architecture)>os_arch_$(TARGET_ARCH).o :
-			tls.c
-			thread.c
-			system_time.c
-			time.c
+			byteorder.S
 			get_stack_frame.S
+			system_time.c
+			thread.c
+			time.c
+			tls.c
 
 			generic_atomic.cpp
 			generic_stack_trace.cpp

src/system/libroot/os/arch/arm64/byteorder.S

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2021, Haiku, Inc. All rights reserved.
+ * Released under the terms of the MIT License
+ */
+
+
+#include <asm_defs.h>
+
+.text
+
+/* float __swap_float(float value) */
+FUNCTION(__swap_float):
+		fmov s0, w0	// Bitcopy float to general register
+		rev w0, w0	// GCC8.3 does this for __builtin_bswap32
+		fmov w0, s0	// and back
+		ret
+FUNCTION_END(__swap_float)
+
+
+/* double __swap_double(double value) */
+FUNCTION(__swap_double):
+		fmov d0, x0	// Bitcopy double to general register
+		rev x0, x0	// GCC8.3 does this for __builtin_bswap64
+		fmov x0, d0	// and back
+		ret
+FUNCTION_END(__swap_double)