Patch "MIPS: UAPI: Ignore __arch_swab{16,32,64} when using MIPS16" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

    MIPS: UAPI: Ignore __arch_swab{16,32,64} when using MIPS16

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     mips-uapi-ignore-__arch_swab-16-32-64-when-using-mips16.patch

and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Yousong Zhou <[email protected]>
Date: Sat, 26 Sep 2015 13:41:43 +0800
Subject: MIPS: UAPI: Ignore __arch_swab{16,32,64} when using MIPS16

From: Yousong Zhou <[email protected]>

commit 71a0a72456b48de972d7ed613b06a22a3aa9057f upstream.

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

Patchwork: https://patchwork.linux-mips.org/patch/11241/

---
 arch/mips/include/uapi/asm/swab.h |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

@@ -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
 }
 #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 */

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/mips-uapi-ignore-__arch_swab-16-32-64-when-using-mips16.patch