Re: [Qemu-devel] [RFC 20/38] tcg/i386: implement fences

[Paolo Bonzini]

On 23/08/2015 17:23, Emilio G. Cota wrote:
> +    case INDEX_op_fence_load:
> +        tcg_out_fence(s, 0xe8);
> +        break;
> +    case INDEX_op_fence_full:
> +        tcg_out_fence(s, 0xf0);
> +        break;
> +    case INDEX_op_fence_store:
> +        tcg_out_fence(s, 0xf8);
> +        break;
> +

lfence and sfence are not needed in generated code; all loads are
acquires and all stores are release on x86.

Also, on targets that do not have MFENCE you want to generate something
like "lock addl $0, (%esp)".

Paolo