Date: Thu, 28 Jan 1999 17:22:01 -0800 (PST) From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: dillon@apollo.backplane.com (Matthew Dillon) Cc: peter.jeremy@auss2.alcatel.com.au, current@FreeBSD.ORG Subject: Re: indent(1) and style(9) (was: btokup() macro in sys/malloc.h) Message-ID: <199901290122.RAA27878@troutmask.apl.washington.edu> In-Reply-To: <199901290033.QAA12211@apollo.backplane.com> from Matthew Dillon at "Jan 28, 1999 4:33:12 pm"
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Matthew Dillon wrote:
> :Luigi Rizzo <luigi@labinfo.iet.unipi.it>
> :>not speaking about vinum, but to me, the indentation of 8 char and
> :...
> :
> :According to most of the coding standards I've read, readability
> :(and hence maintainability) come before efficiency. That said, I
> :agree that efficiency _is_ an issue within the kernel's critical
> :paths (the TCP/IP code being one).
> :
> :Judicious use of inline functions (and macros) should help move
> :code to the left - and may even make it more understandable.
> :
> :Peter
>
> More then judicious use -- inlines are an incredible advantage. Most
> people don't realize that GCC will optimize constant arguments through
> an inline call. Try this:
>
> static __inline
Matt,
int
fubar(int c)
{
if (c & 1)
++c;
if (c & 2)
++c;
return(c);
}
void
fubar2(void)
{
volatile int x;
x = fubar(0);
x = fubar(1);
x = fubar(2);
x = fubar(3);
}
% cc -S -O3 x.c
% cat x.s
fubar2:
pushl %ebp
movl %esp,%ebp
subl $4,%esp
xorl %eax,%eax <----- fubar (0)
movl %eax,-4(%ebp)
movl $3,-4(%ebp) <----- fubar (1)
movl $3,-4(%ebp) <----- fubar (2)
movl $4,-4(%ebp) <----- fubar (3)
leave
ret
--
Steve
finger kargl@troutmask.apl.washington.edu
http://troutmask.apl.washington.edu/~clesceri/kargl.html
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