Some GCC versions (e.g. 4.8.3) can incorrectly inline a function with
MIPS32 instructions into another function with MIPS16 code [1], causing
the assembler to genereate incorrect binary code or fail right away
complaining about unrecognized opcode.
In the case of __arch_swab{16,32}, when inlined by the compiler with
flags `-mips32r2 -mips16 -Os', the assembler can fail with the following
error.
{standard input}:79: Error: unrecognized opcode `wsbh $2,$2'
For performance concerns and to workaround the issue already existing in
older compilers, just ignore these 2 functions when compiling with
mips16 enabled.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55777
Signed-off-by: Yousong Zhou <yszhou4tech@xxxxxxxxx>
---
v2 <- v1
Also ignore __arch_swab64 instead of just __arch_swab{16,32}.
arch/mips/include/uapi/asm/swab.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/mips/include/uapi/asm/swab.h b/arch/mips/include/uapi/asm/swab.h
index 8f2d184..8b9a390 100644
--- a/arch/mips/include/uapi/asm/swab.h
+++ b/arch/mips/include/uapi/asm/swab.h
@@ -8,6 +8,11 @@
#ifndef _ASM_SWAB_H
#define _ASM_SWAB_H
+/*
+ * Enable the optimized version only when compiling without MIPS16.
+ */
+#ifndef __mips16
+
#include <linux/compiler.h>
#include <linux/types.h>
@@ -66,4 +71,5 @@ static inline __attribute_const__ __u64 __arch_swab64(__u64 x)
#define __arch_swab64 __arch_swab64
#endif /* __mips64 */
#endif /* MIPS R2 or newer or Loongson 3A */
+#endif /* ifndef __mips16 */
#endif /* _ASM_SWAB_H */
--
1.7.10.4
