From 1ec8070e58a30bd175a1c7186bff797488e8a17b Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 13 Nov 2020 03:22:23 +0000 Subject: qemu/host-utils: Add wrappers for carry builtins MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit These builtins came in clang 3.8, but are not present in gcc through version 11. Even in clang the optimization is only ideal on x86_64, but never worse than the hand-coding that we currently do. Reviewed-by: Alex Bennée Signed-off-by: Richard Henderson --- include/qemu/host-utils.h | 50 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) (limited to 'include') diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h index cb95626..711b221 100644 --- a/include/qemu/host-utils.h +++ b/include/qemu/host-utils.h @@ -26,6 +26,7 @@ #ifndef HOST_UTILS_H #define HOST_UTILS_H +#include "qemu/compiler.h" #include "qemu/bswap.h" #ifdef CONFIG_INT128 @@ -581,6 +582,55 @@ static inline bool umul64_overflow(uint64_t x, uint64_t y, uint64_t *ret) #endif } +/** + * uadd64_carry - addition with carry-in and carry-out + * @x, @y: addends + * @pcarry: in-out carry value + * + * Computes @x + @y + *@pcarry, placing the carry-out back + * into *@pcarry and returning the 64-bit sum. + */ +static inline uint64_t uadd64_carry(uint64_t x, uint64_t y, bool *pcarry) +{ +#if __has_builtin(__builtin_addcll) + unsigned long long c = *pcarry; + x = __builtin_addcll(x, y, c, &c); + *pcarry = c & 1; + return x; +#else + bool c = *pcarry; + /* This is clang's internal expansion of __builtin_addc. */ + c = uadd64_overflow(x, c, &x); + c |= uadd64_overflow(x, y, &x); + *pcarry = c; + return x; +#endif +} + +/** + * usub64_borrow - subtraction with borrow-in and borrow-out + * @x, @y: addends + * @pborrow: in-out borrow value + * + * Computes @x - @y - *@pborrow, placing the borrow-out back + * into *@pborrow and returning the 64-bit sum. + */ +static inline uint64_t usub64_borrow(uint64_t x, uint64_t y, bool *pborrow) +{ +#if __has_builtin(__builtin_subcll) + unsigned long long b = *pborrow; + x = __builtin_subcll(x, y, b, &b); + *pborrow = b & 1; + return x; +#else + bool b = *pborrow; + b = usub64_overflow(x, b, &x); + b |= usub64_overflow(x, y, &x); + *pborrow = b; + return x; +#endif +} + /* Host type specific sizes of these routines. */ #if ULONG_MAX == UINT32_MAX -- cgit v1.1