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>
This reverts commit e0d8b2ec53.
For at least GCC 4.8.3, adding nomips16 function attribute still cannot
prevent it from being inlined in mips16 context. So revert it first in
preparation for a better workaround.
[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/11240/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
The nomips16 has to be added both as function attribute and assembler
directive.
When only function attribute is specified, the compiler will inline the
function with -Os optimization. The generated assembly code cannot be
correctly assembled because ISA mode switch has to be done through jump
instruction.
When only ".set nomips16" directive is used, the generated assembly code
will use MIPS32 code for the inline assembly template and MIPS16 for the
function return. The compiled binary is invalid:
00403100 <__arch_swab16>:
403100: 7c0410a0 wsbh v0,a0
403104: e820ea31 swc2 $0,-5583(at)
while correct code should be:
00402650 <__arch_swab16>:
402650: 7c0410a0 wsbh v0,a0
402654: 03e00008 jr ra
402658: 3042ffff andi v0,v0,0xffff
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
Cc: Chen Jie <chenj@lemote.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11087/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>
Yousong Zhou