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References: <20170621024831.26019-1-rth@twiddle.net>
	<20170621024831.26019-8-rth@twiddle.net>
From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
In-reply-to: <20170621024831.26019-8-rth@twiddle.net>
Date: Tue, 27 Jun 2017 09:47:22 +0100
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Subject: Re: [Qemu-devel] [PATCH 07/16] tcg: Return NULL temp for
 TCG_CALL_DUMMY_ARG
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To: Richard Henderson <rth@twiddle.net>
Cc: qemu-devel@nongnu.org, aurelien@aurel32.net


Richard Henderson <rth@twiddle.net> writes:

> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/tcg.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tcg/tcg.h b/tcg/tcg.h
> index 3b35344..6c357e7 100644
> --- a/tcg/tcg.h
> +++ b/tcg/tcg.h
> @@ -730,7 +730,7 @@ extern bool parallel_cpus;
>
>  static inline TCGTemp *arg_temp(TCGArg a)
>  {
> -    return &tcg_ctx.temps[a];
> +    return a == TCG_CALL_DUMMY_ARG ? NULL : &tcg_ctx.temps[a];
>  }

It doesn't look like a lot of calls to arg_temp are able to deal with a
NULL return and may well immediately deref the value. Are we sure the
cases the TCG_CALL_DUMMY arg is involved are narrowly defined?

>
>  static inline void tcg_set_insn_param(int op_idx, int arg, TCGArg v)


--
Alex Bennée