From e06049f38074b9533c4beef37d634dad3bd97c73 Mon Sep 17 00:00:00 2001 From: Luis Pires Date: Fri, 29 Oct 2021 16:24:07 -0300 Subject: host-utils: Introduce mulu128 Signed-off-by: Luis Pires Reviewed-by: Richard Henderson Message-Id: <20211029192417.400707-6-luis.pires@eldorado.org.br> Signed-off-by: David Gibson --- include/qemu/host-utils.h | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) (limited to 'include/qemu') diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h index a3a7ced7..ca979dc 100644 --- a/include/qemu/host-utils.h +++ b/include/qemu/host-utils.h @@ -590,6 +590,42 @@ static inline bool umul64_overflow(uint64_t x, uint64_t y, uint64_t *ret) #endif } +/* + * Unsigned 128x64 multiplication. + * Returns true if the result got truncated to 128 bits. + * Otherwise, returns false and the multiplication result via plow and phigh. + */ +static inline bool mulu128(uint64_t *plow, uint64_t *phigh, uint64_t factor) +{ +#if defined(CONFIG_INT128) && \ + (__has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5) + bool res; + __uint128_t r; + __uint128_t f = ((__uint128_t)*phigh << 64) | *plow; + res = __builtin_mul_overflow(f, factor, &r); + + *plow = r; + *phigh = r >> 64; + + return res; +#else + uint64_t dhi = *phigh; + uint64_t dlo = *plow; + uint64_t ahi; + uint64_t blo, bhi; + + if (dhi == 0) { + mulu64(plow, phigh, dlo, factor); + return false; + } + + mulu64(plow, &ahi, dlo, factor); + mulu64(&blo, &bhi, dhi, factor); + + return uadd64_overflow(ahi, blo, phigh) || bhi != 0; +#endif +} + /** * uadd64_carry - addition with carry-in and carry-out * @x, @y: addends -- cgit v1.1