Re: [Qemu-devel] [PATCH v2] Use proper term in TCG README

[Peter Maydell]

On 14 March 2013 08:06, 陳韋任 (Wei-Ren Chen) <address@hidden> wrote:
>   In TCG, "target" means the host architecture for which TCG generates
> the code. Using "guest" rather than "target" to make the document more
> consistent.

Thanks. I've tweaked the wording a little in one sentence below;
otherwise it looks good.

> Signed-off-by: Chen Wei-Ren <address@hidden>
> ---
>  tcg/README | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/tcg/README b/tcg/README
> index 934e7af..00d4751 100644
> --- a/tcg/README
> +++ b/tcg/README
> @@ -14,6 +14,9 @@ the emulated architecture. As TCG started as a generic C 
> backend used
>  for cross compiling, it is assumed that the TCG target is different
>  from the host, although it is never the case for QEMU.
>
> +In this document, we uses "guest" to specify what architecture we are

"use".


> +emulating, and "target" means on what machine we are running QEMU.

"emulating; "target" always means the TCG target, the machine on which
we are running QEMU."

> +
>  A TCG "function" corresponds to a QEMU Translated Block (TB).
>
>  A TCG "temporary" is a variable only live in a basic
> @@ -379,7 +382,7 @@ double-word product T0.  The later is returned in two 
> single-word outputs.
>
>  Similar to mulu2, except the two inputs T1 and T2 are signed.
>
> -********* 64-bit target on 32-bit host support
> +********* 64-bit guest on 32-bit host support
>
>  The following opcodes are internal to TCG.  Thus they are to be implemented 
> by
>  32-bit host code generators, but are not to be emitted by guest translators.
> @@ -521,9 +524,9 @@ register.
>    a better generated code, but it reduces the memory usage of TCG and
>    the speed of the translation.
>
> -- Don't hesitate to use helpers for complicated or seldom used target
> +- Don't hesitate to use helpers for complicated or seldom used guest
>    instructions. There is little performance advantage in using TCG to
> -  implement target instructions taking more than about twenty TCG
> +  implement guest instructions taking more than about twenty TCG
>    instructions. Note that this rule of thumb is more applicable to
>    helpers doing complex logic or arithmetic, where the C compiler has
>    scope to do a good job of optimisation; it is less relevant where
> @@ -531,9 +534,9 @@ register.
>    inline TCG may still be faster for longer sequences.
>
>  - The hard limit on the number of TCG instructions you can generate
> -  per target instruction is set by MAX_OP_PER_INSTR in exec-all.h --
> +  per guest instruction is set by MAX_OP_PER_INSTR in exec-all.h --
>    you cannot exceed this without risking a buffer overrun.
>
>  - Use the 'discard' instruction if you know that TCG won't be able to
>    prove that a given global is "dead" at a given program point. The
> -  x86 target uses it to improve the condition codes optimisation.
> +  x86 guest uses it to improve the condition codes optimisation.
> --
> 1.7.12.3

-- PMM