Re: [PATCH v2 07/19] target/i386: introduce flags writeback mechanism

[Richard Henderson <richard.henderson@linaro.org>]

On 10/19/23 03:46, Paolo Bonzini wrote:
> +    /*
> +     * Write back flags after last memory access.  Some newer ALU instructions, as
> +     * well as SSE instructions, write flags in the gen_* function, but that can
> +     * cause incorrect tracking of CC_OP for instructions that write to both memory
> +     * and flags.
> +     */
> +    if (decode.cc_op != -1) {
> +        if (decode.cc_dst) {
> +            tcg_gen_mov_tl(cpu_cc_dst, decode.cc_dst);
> +        }
> +        if (decode.cc_src) {
> +            tcg_gen_mov_tl(cpu_cc_src, decode.cc_src);
> +        }
> +        if (decode.cc_src2) {
> +            tcg_gen_mov_tl(cpu_cc_src2, decode.cc_src2);
> +        }
> +        if (decode.cc_op == CC_OP_DYNAMIC) {
> +            tcg_gen_mov_i32(cpu_cc_op, decode.cc_op_dynamic);
> +        } else {
> +            assert(!decode.cc_op_dynamic);
> +        }
> +        set_cc_op(s, decode.cc_op);
> +    } else {
> +        assert(!decode.cc_dst);
> +        assert(!decode.cc_src);
> +        assert(!decode.cc_src2);
> +        assert(!decode.cc_op_dynamic);
> +    }

I suggest you use cc_op_live[] to ensure that each output is present if USES_CC_* is set, 
and absent otherwise. Obviously that's not possible for CC_OP_DYNAMIC, but for everything 
else...


r~