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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 11 Jan 2016 22:29:42 +0000
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Subject: Re: [Qemu-devel] [RFC 0/2] tcg-icount: Add and use
 tcg_set_insn_param to update tcg insn params
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To: =?UTF-8?Q?Llu=C3=ADs_Vilanova?= <vilanova@ac.upc.edu>
Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, QEMU Developers <qemu-devel@nongnu.org>, Richard Henderson <rth@twiddle.net>

On 11 January 2016 at 20:16, Llu=C3=ADs Vilanova <vilanova@ac.upc.edu> wrot=
e:
> Great! I implemented a similar thing long time ago. In my case the machin=
ery is
> completely hidden under the concept of "value promises" in TCG (i.e., the=
 user
> does not need to know about TCG internals like tcg_op_buf_count):
>
>    // create promise
>    TCGv_promise_i32 imm_p;
>    TCGv_i32 imm =3D tcg_const_promise_i32(&imm_p); // akin to tcg_const_i=
32()
>    ...
>    // operate with promised immediate 'imm'
>    ...
>    // resolve promised value
>    tcg_set_promise_i32(imm_p, resolved_value);

I think this is definitely a nicer API if we're going to
have more than a very few uses -- gen_icount kind of gets
away with looking under the hood of the tcg data structures
because it's a sort of internal thing itself, but wider
use would definitely benefit from a more formal API.

thanks
-- PMM