From: Dmitry Bely <dbely@mail.ru>
To: caml-list@inria.fr
Subject: Re: [Caml-list] Timing Ocaml
Date: Mon, 10 Jun 2002 16:02:12 +0400 [thread overview]
Message-ID: <sn3v735n.fsf@mail.ru> (raw)
In-Reply-To: <4.3.2.7.2.20020609232056.029ec260@mail.d6.com> (Chris Hecker's message of "Sun, 09 Jun 2002 23:24:29 -0700")
Chris Hecker <checker@d6.com> writes:
>>* The GNU C compiler gcc is recommended, as the bytecode
>> interpreter takes advantage of gcc-specific features to enhance
>> performance.
>>What is the nature of these optimizations?
>
> GCC lets you take the address of a label. You can see in
> byterun/interp.c that it uses a jump table instead of a switch when
> you're using GCC.
>
> At least, that's what it looks like.
I would rather say that gcc allows to force register allocation for some
specific variable, while MSVC always ignore "register" specifier.
#if defined(__GNUC__) && !defined(DEBUG)
[...]
#ifdef __i386__
#define PC_REG asm("%esi")
#define SP_REG asm("%edi")
#define ACCU_REG
#endif
[...]
#endif
/* The interpreter itself */
value interprete(code_t prog, asize_t prog_size)
{
#ifdef PC_REG
register code_t pc PC_REG;
register value * sp SP_REG;
register value accu ACCU_REG;
#else
register code_t pc;
register value * sp;
register value accu;
#endif
In the same time MSVC has very good optimizer and it is very strange, that
two explicit register variables lead to 30% performance gain...
Hope to hear from you soon,
Dmitry
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next prev parent reply other threads:[~2002-06-10 12:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-10 5:35 Blair Zajac
2002-06-10 6:24 ` Chris Hecker
2002-06-10 12:02 ` Dmitry Bely [this message]
2002-06-10 12:50 ` Remi VANICAT
2002-06-10 14:19 ` Lionel Fourquaux
2002-06-10 15:01 ` Xavier Leroy
2002-06-10 16:29 ` Dmitry Bely
2002-06-10 16:49 ` Lionel Fourquaux
2002-06-11 8:28 ` Dmitry Bely
2002-06-11 9:08 ` Xavier Leroy
2002-06-11 12:52 ` Mattias Waldau
2002-06-10 18:19 ` Blair Zajac
2002-06-11 9:23 ` Florian Hars
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