Re: i386 inline-asm string functions - some questions

Denis Zaitsev <[email protected]> writes:

> On Mon, Dec 29, 2003 at 12:31:52AM -0500, Daniel Jacobowitz wrote:
>> Funny, I conducted this experiment last week and found quite the
>> opposite.  Compiling the demangler and a smallish yacc parser
>> with -D__NO_STRING_INLINES cost about 20% in runtime.
>
> -D__NO_STRING_INLINES just puts the inlining off.  But nobody here
> tells about the inline/noinline comparing.  Of course, inlining is
> better at speed.  The comparison is doing between some versions of the
> inlining.

No.  There is no "of course" here.  If your inlined functions blow out
the instruction cache, it may wind up being a net lose.  Same if the
out-of-line memcpy takes several more instructions to set up but makes
damn sure to do aligned memory accesses (full-bus-width loads,
nontemporal store, prefetches, etc etc etc), whereas the inline one
doesn't.

zw