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>
---
arch/mips/include/uapi/asm/swab.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/mips/include/uapi/asm/swab.h b/arch/mips/include/uapi/asm/swab.h
index 8f2d184..8396d5a 100644
--- a/arch/mips/include/uapi/asm/swab.h
+++ b/arch/mips/include/uapi/asm/swab.h
@@ -16,6 +16,10 @@
#if (defined(__mips_isa_rev) && (__mips_isa_rev >= 2)) || \
defined(_MIPS_ARCH_LOONGSON3A)
+/*
+ * Enable the optimized version only when compiling without MIPS16.
+ */
+#ifndef __mips16
static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
{
__asm__(
@@ -44,6 +48,7 @@ static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
return x;
}
#define __arch_swab32 __arch_swab32
+#endif /* ifndef __mips16 */
/*
* Having already checked for MIPS R2, enable the optimized version for
--
1.7.10.4
