Fix unified syntax in ARM inline assembly

GCC 4.9 always emits assembly with divided syntax. Setting unified
syntax in inline assembly causes the assembler to complain about
GCC's generated code, because the directive extends past the scope
of the inline asm. Fix this by setting divided mode at the end of
the inline assembly block.

The assembler directives are hidden behind macros because later
versions of GCC won't need this workaround: they can be told to
use the unified syntax with -masm-syntax-unified.

Change-Id: Ic09e729e5bbb6fd44d08dac348daf6f55c75d7d8

1 files changed, 10 insertions, 0 deletions

diff --git a/firmware/export/config.h b/firmware/export/config.h
index 19ee03b4c7..49cd6d610c 100644
--- a/firmware/export/config.h
+++ b/firmware/export/config.h
@@ -1005,6 +1005,16 @@ Lyre prototype 1 */
 #define ROCKBOX_STRICT_ALIGN 1
 #endif
 
+/*
+ * These macros are for switching on unified syntax in inline assembly.
+ * Older versions of GCC emit assembly in divided syntax with no option
+ * to enable unified syntax.
+ *
+ * FIXME: This needs to be looked at after the toolchain bump
+ */
+#define BEGIN_ARM_ASM_SYNTAX_UNIFIED ".syntax unified\n"
+#define END_ARM_ASM_SYNTAX_UNIFIED   ".syntax divided\n"
+
 #if defined(CPU_ARM) && defined(__ASSEMBLER__)
 .syntax unified
 /* ARMv4T doesn't switch the T bit when popping pc directly, we must use BX */