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Date: Sun, 18 Sep 2011 07:49:15 +0200
From: Stefan Weil <weil@mail.berlios.de>
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Subject: Re: [Qemu-devel] [PATCH 5/8] tcg: Add interpreter for bytecode
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To: Andi Kleen <andi@firstfloor.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>

Am 18.09.2011 06:03, schrieb Andi Kleen:
> Stefan Weil <weil@mail.berlios.de> writes:
>> +
>> + switch (opc) {
>> + case INDEX_op_end:
>> + case INDEX_op_nop:
>> + break;
>
> You could probably get some more speed out of this by using a threaded
> interpreter with gcc's computed goto extension. That's typically
> significantly faster than a plain switch in a loop.
>
> static void *ops[] = {
> &&op1,
> &&op2,
> ...
> };
>
> #define NEXT() goto *ops[*tb_ptr++];
>
> op1:
> ...
> NEXT();
>
> -Andi

Is there really any difference in the generated code?
gcc already uses a jump table internally to handle the
switch cases.

- Stefan