commit ebabcf17bcd7ce968b1631ebe08236275698f39b upstream.

GCC7 is a bit too eager to generate suboptimal __multi3 calls (128bit
multiply with 128bit result) for MIPS64r6 builds, even in code which
doesn't explicitly use 128bit types, such as the following:

unsigned long func(unsigned long a, unsigned long b)
{
	return a > (~0UL) / b;
}

Which GCC rearanges to:

return (unsigned __int128)a * (unsigned __int128)b > 0xffffffffffffffff;

Therefore implement __multi3, but only for MIPS64r6 with GCC7 as under
normal circumstances we wouldn't expect any calls to __multi3 to be
generated from kernel code.

Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: James Hogan <jhogan@kernel.org>
Tested-by: Waldemar Brodkorb <wbx@openadk.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Maciej W. Rozycki <macro@mips.com>
Cc: Matthew Fortune <matthew.fortune@mips.com>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17890/
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/mips/lib/libgcc.h:21: ERROR: open brace '{' following union go on the same line

Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
To: linux-kernel@vger.kernel.org
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: linux-mips@linux-mips.org
Cc: linux-sh@vger.kernel.org
Patchwork: http://patchwork.linux-mips.org/patch/1007/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

    
It took a while longer than on other architectures but gcc has finally
started to strike us as well ...
    
This also fixes the damage by 6edfba1b33c701108717f4e036320fc39abe1912.
    
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>