Re: [PATCH 02/72] qemu/host-utils: Add wrappers for overflow builtins

[Alex Bennée]

Richard Henderson <richard.henderson@linaro.org> writes:

> These builtins came in with gcc 5 and clang 3.8, which are
> slightly newer than our supported minimum compiler versions.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/qemu/host-utils.h | 225 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 225 insertions(+)
>
> diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
> index f1e52851e0..fd76f0cbd3 100644
> --- a/include/qemu/host-utils.h
> +++ b/include/qemu/host-utils.h
> @@ -356,6 +356,231 @@ static inline uint64_t revbit64(uint64_t x)
>  #endif
>  }
>  
> +/**
> + * sadd32_overflow - addition with overflow indication
> + * @x, @y: addends
> + * @ret: Output for sum
> + *
> + * Computes *@ret = @x + @y, and returns true if and only if that
> + * value has been truncated.
> + */
> +static inline bool sadd32_overflow(int32_t x, int32_t y, int32_t *ret)
> +{
> +#if __has_builtin(__builtin_add_overflow) || __GNUC__ >= 5

I was wondering if having multiple compiler tests means we should move
this test into compiler.h but it doesn't seem we've done it in any other
case except libvixl's GCC_VERSION_OR_NEWER helper.

> +/**
> + * smul64_overflow - multiplication with overflow indication
> + * @x, @y: Input multipliers
> + * @ret: Output for product
> + *
> + * Computes *@ret = @x * @y, and returns true if and only if that
> + * value has been truncated.
> + */
> +static inline bool smul64_overflow(int64_t x, int64_t y, int64_t *ret)
> +{
> +#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
> +    return __builtin_mul_overflow(x, y, ret);
> +#else
> +    uint64_t hi, lo;
> +    muls64(&lo, &hi, x, y);
> +    *ret = lo;
> +    return hi != ((int64_t)lo >> 63);
> +#endif
> +}
> +
> +/**
> + * umul32_overflow - multiplication with overflow indication
> + * @x, @y: Input multipliers
> + * @ret: Output for product
> + *
> + * Computes *@ret = @x * @y, and returns true if and only if that
> + * value has been truncated.
> + */
> +static inline bool umul32_overflow(uint32_t x, uint32_t y, uint32_t *ret)
> +{
> +#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
> +    return __builtin_mul_overflow(x, y, ret);
> +#else
> +    uint64_t z = (uint64_t)x * y;
> +    *ret = z;
> +    return z > UINT32_MAX;
> +#endif
> +}
> +
> +/**
> + * smul64_overflow - multiplication with overflow indication

c&p error.

> + * @x, @y: Input multipliers
> + * @ret: Output for product
> + *
> + * Computes *@ret = @x * @y, and returns true if and only if that
> + * value has been truncated.
> + */
> +static inline bool umul64_overflow(uint64_t x, uint64_t y, uint64_t *ret)
> +{
> +#if __has_builtin(__builtin_mul_overflow) || __GNUC__ >= 5
> +    return __builtin_mul_overflow(x, y, ret);
> +#else
> +    uint64_t hi;
> +    mulu64(ret, &hi, x, y);
> +    return hi != 0;
> +#endif
> +}
> +
>  /* Host type specific sizes of these routines.  */
>  
>  #if ULONG_MAX == UINT32_MAX

Otherwise:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée