On Wed, 3 May 2023 at 08:29, Richard Henderson
<richard.hender...@linaro.org> wrote:
>
> There is an edge condition prior to gcc13 for which optimization
> is required to generate 16-byte atomic sequences. Detect this.
>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> accel/tcg/ldst_atomicity.c.inc | 38 ++++++++++++++++++-------
> meson.build | 52 ++++++++++++++++++++++------------
> 2 files changed, 61 insertions(+), 29 deletions(-)
>
> @@ -676,28 +695,24 @@ static inline void store_atomic8(void *pv, uint64_t val)
> *
> * Atomically store 16 aligned bytes to @pv.
> */
> -static inline void store_atomic16(void *pv, Int128 val)
> +static inline void ATTRIBUTE_ATOMIC128_OPT
> +store_atomic16(void *pv, Int128Alias val)
> {
> #if defined(CONFIG_ATOMIC128)
> __uint128_t *pu = __builtin_assume_aligned(pv, 16);
> - Int128Alias new;
> -
> - new.s = val;
> - qatomic_set__nocheck(pu, new.u);
> + qatomic_set__nocheck(pu, val.u);
> #elif defined(CONFIG_CMPXCHG128)
> __uint128_t *pu = __builtin_assume_aligned(pv, 16);
> __uint128_t o;
> - Int128Alias n;
>
> /*
> * Without CONFIG_ATOMIC128, __atomic_compare_exchange_n will always
> * defer to libatomic, so we must use __sync_val_compare_and_swap_16
> * and accept the sequential consistency that comes with it.
> */
> - n.s = val;
> do {
> o = *pu;
> - } while (!__sync_bool_compare_and_swap_16(pu, o, n.u));
> + } while (!__sync_bool_compare_and_swap_16(pu, o, val.u));
> #else
> qemu_build_not_reached();
> #endif
Should this change be in a different patch? It doesn't
seem related to the meson detection.
Otherwise
Reviewed-by: Peter Maydell <peter.mayd...@linaro.org>
thanks
-- PMM
