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Banner advertising on our site currently available from just $5! # DJGPP asm Old topic! Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic. 6 replies to this topic ### #1bosjoh Members - Reputation: 122 Like Likes Like Posted 16 December 1999 - 06:39 PM Anyone knows how to program this: void buf_to_screen(){ asm{ mov edi, screen mov esi, buffer mov ecx, 76800 rep movsd }; }; In DJGPP? Sponsor: ### #2Aeetes Members - Reputation: 122 Like Likes Like Posted 16 December 1999 - 04:17 AM I'm not 100% positive (I stopped using DJGPP about a year ago), but I believe it would look like this: (DJGPP uses AT&T syntax) code: void buf_to_screen() { asm("movl$0x12C00 %ecx\n\t"        "cld\n\t"        "rep\n\t"        "movsd"        :        : "S" (buffer), "D" (screen)        : "%ecx", "%esi", "%edi"    );}

The stuff at the end on the ":" lines are where you declare your output registers, registers loaded, and your clobber list, in that order.

As I said before, I haven't programmed in DJGPP in a while (or recently done much inline asm for that matter ) so this might not be totally correct, but I hope it helps.

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Where's my Golden Fleece?

[This message has been edited by Aeetes (edited December 16, 1999).]

### #3mhkrause  Members   -  Reputation: 122

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Posted 16 December 1999 - 07:24 AM

I haven't done anything with DJGPP in about two years, but the above looks correct, except that "movsd" should be "movsl"

There's a great tutorial on DJGPP ASM, I think written by "Brennan something." Should be able to find a link to it off of DJ Delorie's site.

### #4bosjoh  Members   -  Reputation: 122

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Posted 16 December 1999 - 08:07 AM

Thanks!
I figured out some of the asm (i knew %eax etc. and movl src, dest).
I was having most of the problems with the things you should put behind the semicolons.

### #5bosjoh  Members   -  Reputation: 122

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Posted 16 December 1999 - 09:14 AM

hmm...
it doesn't work.
Output:
Error: invalid 'asm' statement
Error: Fixed or forbidden register 4 (si) was spilled for class SIREG

If I remove the last (semicolon) line I get one error.

Error: operand number missing after %-letter

Any solutions?

### #6Aeetes  Members   -  Reputation: 122

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Posted 16 December 1999 - 10:38 AM

After seeing the error output you got I think I see what is wrong from that listing I posted.

• On the third ":" line for the clobbered list... I think that the error about si being "spilled" is caused because %esi (and additionally %edi) shouldn't be on the clobbered list, only %ecx was clobbered by the code given. This is because GCC knows about the registers being loaded into, so you don't have to tell it that they are clobbered.

• The first set of error messages were caused by this I think. I also forgot that since we are modifying some memory, we need to add "memory" to the clobbered list.

• The error message you got on the second pass was caused by the leaving out of an extra % when prefixing the register ecx. In extended inline assembly (what it is called when using the ":" lines), registers have to be prefixed by two %'s, e.g. "%%ecx". A single % is used before a number to identify an input (applies when using general "g" and "r" instead of specific "D" and "S" in our case in declaring inputs). DJGPP needs the two %'s to distinguish between the two uses.

Therefore I believe the code should actually look like this:
code:
void buffer_to_screen() {    asm("movl $0x12C00 %%ecx\n\t" "cld\n\t" "reg\n\t" "movsl" : : "S" (buffer), "D" (screen) : "$ecx", "memory"    );}

Here are a couple pages that you could check out for more detailed information:

Hope this gets you running...

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Where's my Golden Fleece?

[This message has been edited by Aeetes (edited December 16, 1999).]

### #7bosjoh  Members   -  Reputation: 122

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Posted 16 December 1999 - 06:39 PM

Thanx again.

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