diff options
| -rw-r--r-- | arch/x86/include/asm/div64.h | 19 | ||||
| -rw-r--r-- | include/linux/math64.h | 11 | ||||
| -rw-r--r-- | lib/math/div64.c | 40 |
3 files changed, 56 insertions, 14 deletions
diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h index 6d8a3de3f43a..30fd06ede751 100644 --- a/arch/x86/include/asm/div64.h +++ b/arch/x86/include/asm/div64.h @@ -60,6 +60,12 @@ static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) } #define div_u64_rem div_u64_rem +/* + * gcc tends to zero extend 32bit values and do full 64bit maths. + * Define asm functions that avoid this. + * (clang generates better code for the C versions.) + */ +#ifndef __clang__ static inline u64 mul_u32_u32(u32 a, u32 b) { u32 high, low; @@ -71,6 +77,19 @@ static inline u64 mul_u32_u32(u32 a, u32 b) } #define mul_u32_u32 mul_u32_u32 +static inline u64 add_u64_u32(u64 a, u32 b) +{ + u32 high = a >> 32, low = a; + + asm ("addl %[b], %[low]; adcl $0, %[high]" + : [low] "+r" (low), [high] "+r" (high) + : [b] "rm" (b) ); + + return low | (u64)high << 32; +} +#define add_u64_u32 add_u64_u32 +#endif + /* * __div64_32() is never called on x86, so prevent the * generic definition from getting built. diff --git a/include/linux/math64.h b/include/linux/math64.h index e889d850b7f1..cc305206d89f 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -158,6 +158,17 @@ static inline u64 mul_u32_u32(u32 a, u32 b) } #endif +#ifndef add_u64_u32 +/* + * Many a GCC version also messes this up. + * Zero extending b and then spilling everything to stack. + */ +static inline u64 add_u64_u32(u64 a, u32 b) +{ + return a + b; +} +#endif + #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__) #ifndef mul_u64_u32_shr diff --git a/lib/math/div64.c b/lib/math/div64.c index 18a9ba26c418..bb57a48ce36a 100644 --- a/lib/math/div64.c +++ b/lib/math/div64.c @@ -186,33 +186,45 @@ EXPORT_SYMBOL(iter_div_u64_rem); #endif #if !defined(mul_u64_add_u64_div_u64) || defined(test_mul_u64_add_u64_div_u64) -u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d) -{ + +#define mul_add(a, b, c) add_u64_u32(mul_u32_u32(a, b), c) + #if defined(__SIZEOF_INT128__) && !defined(test_mul_u64_add_u64_div_u64) +static inline u64 mul_u64_u64_add_u64(u64 *p_lo, u64 a, u64 b, u64 c) +{ /* native 64x64=128 bits multiplication */ u128 prod = (u128)a * b + c; - u64 n_lo = prod, n_hi = prod >> 64; + + *p_lo = prod; + return prod >> 64; +} #else - /* perform a 64x64=128 bits multiplication manually */ - u32 a_lo = a, a_hi = a >> 32, b_lo = b, b_hi = b >> 32; +static inline u64 mul_u64_u64_add_u64(u64 *p_lo, u64 a, u64 b, u64 c) +{ + /* perform a 64x64=128 bits multiplication in 32bit chunks */ u64 x, y, z; /* Since (x-1)(x-1) + 2(x-1) == x.x - 1 two u32 can be added to a u64 */ - x = (u64)a_lo * b_lo + (u32)c; - y = (u64)a_lo * b_hi + (u32)(c >> 32); - y += (u32)(x >> 32); - z = (u64)a_hi * b_hi + (u32)(y >> 32); - y = (u64)a_hi * b_lo + (u32)y; - z += (u32)(y >> 32); - x = (y << 32) + (u32)x; - - u64 n_lo = x, n_hi = z; + x = mul_add(a, b, c); + y = mul_add(a, b >> 32, c >> 32); + y = add_u64_u32(y, x >> 32); + z = mul_add(a >> 32, b >> 32, y >> 32); + y = mul_add(a >> 32, b, y); + *p_lo = (y << 32) + (u32)x; + return add_u64_u32(z, y >> 32); +} #endif +u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d) +{ + u64 n_lo, n_hi; + + n_hi = mul_u64_u64_add_u64(&n_lo, a, b, c); + if (!n_hi) return div64_u64(n_lo, d); |