 Gcc -o4 Flag, Is it different than -O3 |
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 Mar 27 2007, 10:04 AM
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#1
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 Group: Members Posts: 902 Joined: 22-May 04 Member No.: 3,385  |
I'm playing around with optimizing compiled packages to run fine on Ångström, but the question isn't really Ångström-specific.
I've seen on Meanie's blog on building Firefox natively that he used the -O4 option in CFLAGS. I've looked but not found anything substantive on this flag. One Finnish page on the web states that if -On has n higher than 3, then the flag is automatically interpreted as -O3. Is this so? Or is there a difference between these? |
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Mar 27 2007, 01:18 PM
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#2
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 Group: Admin Posts: 3,277 Joined: 29-July 04 From: Cambridge, England Member No.: 4,149 |
that's using the Spinal Tap version of the compiler - everyone else's goes up to O3, but the 'tap' version goes up to O4.
 --- I wonder whether anyone will understand this joke? |
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Mar 27 2007, 03:16 PM
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#3
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 Group: Members Posts: 2,821 Joined: 13-September 04 From: Wasilla Ak. Member No.: 4,572 |
QUOTE(speculatrix @ Mar 27 2007, 09:18 PM) that's using the Spinal Tap version of the compiler - everyone else's goes up to O3, but the 'tap' version goes up to O4. --- I wonder whether anyone will understand this joke?  11 |
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Mar 27 2007, 11:42 PM
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#4
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 Group: Members Posts: 2,808 Joined: 21-March 05 From: Sydney, Australia Member No.: 6,686 |
QUOTE(adf @ Mar 28 2007, 09:16 AM) QUOTE(speculatrix @ Mar 27 2007, 09:18 PM) that's using the Spinal Tap version of the compiler - everyone else's goes up to O3, but the 'tap' version goes up to O4. --- I wonder whether anyone will understand this joke? 11 oh man, these geek jokes are way over my head. can someone explain it so some dummy like me can understand it? |
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Mar 28 2007, 02:17 AM
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#5
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Group: Admin Posts: 3,277 Joined: 29-July 04 From: Cambridge, England Member No.: 4,149 |
If you haven't seen the film "Spinal Tap", the joke won't make any sense.
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Mar 28 2007, 04:58 AM
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#6
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Group: Members Posts: 902 Joined: 22-May 04 Member No.: 3,385 |
QUOTE(speculatrix @ Mar 28 2007, 11:17 AM) If you haven't seen the film "Spinal Tap", the joke won't make any sense. Didn't get the joke either...How about the original issue though, is there really an -O4 flag that furthers optimization, or is it just the same as -O3? |
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Mar 28 2007, 05:00 AM
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#7
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 Group: Members Posts: 1,014 Joined: 4-January 05 From: Enschede, The Netherlands Member No.: 6,107 |
QUOTE(ShiroiKuma @ Mar 28 2007, 12:58 PM) QUOTE(speculatrix @ Mar 28 2007, 11:17 AM) If you haven't seen the film "Spinal Tap", the joke won't make any sense. Didn't get the joke either...How about the original issue though, is there really an -O4 flag that furthers optimization, or is it just the same as -O3? Just keep in mind that you're reading from *slow* media into a tiny amount of RAM, so 'optimized' binaries will execute slower in the end. I heard the people at nokia use -Os for certain applications because execution time is IO-limited. |
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Mar 31 2007, 11:04 PM
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#8
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 Group: Members Posts: 2,003 Joined: 16-April 04 From: the Netherlands && /dev/null Member No.: 2,882 |
Well then, i have another curiosity question: how would a Firefox build with -O2 optimization (which seems to be very common for compiling Z apps) compared with the one with -O4?
When do we use which level of optimization? And how do we know? :? |
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Apr 1 2007, 12:11 AM
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#9
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 Group: Members Posts: 1,565 Joined: 7-April 05 From: Sydney, Australia Member No.: 6,806 |
just stick with -O2, -O3 or higer dont always produce faster binaries and somtimes will not compile (as i have found out)
if you really need spped -O640K should be good enough for anyone |
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Apr 1 2007, 09:44 AM
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#10
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Group: Members Posts: 902 Joined: 22-May 04 Member No.: 3,385 |
QUOTE(Da_Blitz @ Apr 1 2007, 09:11 AM) if you really need spped -O640K should be good enough for anyone What does this one do? And how does it compare in terms of speed, subjectively what you feel when using the compiled app, with -O2 or -O3 ? |
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Apr 1 2007, 10:14 AM
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#11
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Group: Members Posts: 2,821 Joined: 13-September 04 From: Wasilla Ak. Member No.: 4,572 |
QUOTE(ShiroiKuma @ Apr 1 2007, 05:44 PM) QUOTE(Da_Blitz @ Apr 1 2007, 09:11 AM) if you really need spped -O640K should be good enough for anyone What does this one do? And how does it compare in terms of speed, subjectively what you feel when using the compiled app, with -O2 or -O3 ? Wasn't that MS humor? |
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