Re: [Flightgear-devel] [patch] Improved forests

[Gene B. <ge...@de...>]

On Thu, 28 Jul 2011, Jari Häkkinen wrote:

>>> Are you sure about that? I just tried it with a little example and at least
>>> gcc compiles both variants to the exact same assembly code. Tried it with and
>>> without -O2.
>>>
>> That would freak me out.  Doesn't "++j" mean "increment j, then test"
>> whereas "j++" means "test j, then increment"?
>
> No, for a for loop
>
> for ( [1]; [2]; [3] )
>
> where [3] is ++j will increment j before use. However, in an
> if-statement the complete statement [3] is evaluated before the test [2]
> is done. If the compiler is smart it will produce the fastest binary
> code regardless ++j or j++. However, if the [3] is more complicated like
> a hypothetical i = ++j + k the compiler will most probably generate
> different binary code (compared to i = ++j + k).

Right, but j++ will increment _after_ it's used, correct?  So how could 
++j vs j++ generate the same assembly code and be correct?

g.

-- 
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.simpits.org/geneb - The Me-109F/X Project
Some people collect things for a hobby.  Geeks collect hobbies.

ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://www.scarletdme.org - Get it _today_!

Political correctness is a doctrine, fostered by a delusional, illogical
minority, and rabidly promoted by an unscrupulous mainstream media, which
holds forth the proposition that it is entirely possible to pick up a turd
by the clean end.