linux/arch/mips/lib/libgcc.h
James Hogan ebabcf17bc MIPS: Implement __multi3 for GCC7 MIPS64r6 builds
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/
2018-01-11 14:40:31 +01:00

44 lines
682 B
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_LIBGCC_H
#define __ASM_LIBGCC_H
#include <asm/byteorder.h>
typedef int word_type __attribute__ ((mode (__word__)));
#ifdef __BIG_ENDIAN
struct DWstruct {
int high, low;
};
struct TWstruct {
long long high, low;
};
#elif defined(__LITTLE_ENDIAN)
struct DWstruct {
int low, high;
};
struct TWstruct {
long long low, high;
};
#else
#error I feel sick.
#endif
typedef union {
struct DWstruct s;
long long ll;
} DWunion;
#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6)
typedef int ti_type __attribute__((mode(TI)));
typedef union {
struct TWstruct s;
ti_type ti;
} TWunion;
#endif
#endif /* __ASM_LIBGCC_H */