generic: fix unrecognized opcode wsbh when building for MIPS16.

The issue was found and reported by hynman [1] when compiling reaver for ar71xx
(Big Endian MIPS).

    {standard input}: Assembler messages:
    {standard input}:79: Error: unrecognized opcode `wsbh $2,$2'
    {standard input}:90: Error: unrecognized opcode `wsbh $3,$17'
    {standard input}:208: Error: unrecognized opcode `wsbh $2,$2'
    make[3]: *** [builder.o] Error 1

The patch was already in upstream since kernel release 4.3-rc5.

 [1] https://github.com/openwrt/packages/commit/1e29676a8ac74f797f8ca799364681cec575ae6f#commitcomment-12901931

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

SVN-Revision: 47322

1 files changed, 58 insertions, 0 deletions

diff --git a/target/linux/generic/patches-3.18/133-MIPS-UAPI-Ignore-__arch_swab-16-32-64-when-using-MIP.patch b/target/linux/generic/patches-3.18/133-MIPS-UAPI-Ignore-__arch_swab-16-32-64-when-using-MIP.patch
new file mode 100644
index 0000000000..d8f25ac1fd
--- /dev/null
+++ b/target/linux/generic/patches-3.18/133-MIPS-UAPI-Ignore-__arch_swab-16-32-64-when-using-MIP.patch
@@ -0,0 +1,58 @@
+From 71a0a72456b48de972d7ed613b06a22a3aa9057f Mon Sep 17 00:00:00 2001
+From: Yousong Zhou <yszhou4tech@gmail.com>
+Date: Sat, 26 Sep 2015 13:41:43 +0800
+Subject: [PATCH] MIPS: UAPI: Ignore __arch_swab{16,32,64} when using MIPS16
+
+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] Inlining nomips16 function into mips16 function can result in
+     undefined builtins, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55777
+
+Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
+Cc: Maciej W. Rozycki <macro@linux-mips.org>
+Cc: linux-mips@linux-mips.org
+Patchwork: https://patchwork.linux-mips.org/patch/11241/
+Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
+---
+ arch/mips/include/uapi/asm/swab.h |    7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+diff --git a/arch/mips/include/uapi/asm/swab.h b/arch/mips/include/uapi/asm/swab.h
+index 8f2d184..23cd9b1 100644
+--- a/arch/mips/include/uapi/asm/swab.h
++++ b/arch/mips/include/uapi/asm/swab.h
+@@ -13,8 +13,9 @@
+ 
+ #define __SWAB_64_THRU_32__
+ 
+-#if (defined(__mips_isa_rev) && (__mips_isa_rev >= 2)) ||		\
+-    defined(_MIPS_ARCH_LOONGSON3A)
++#if !defined(__mips16) &&					\
++	((defined(__mips_isa_rev) && (__mips_isa_rev >= 2)) ||	\
++	 defined(_MIPS_ARCH_LOONGSON3A))
+ 
+ static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
+ {
+@@ -65,5 +66,5 @@ 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 /* (not __mips16) and (MIPS R2 or newer or Loongson 3A) */
+ #endif /* _ASM_SWAB_H */
+-- 
+1.7.10.4
+