Xref: news2.mv.net comp.os.msdos.djgpp:2146
From: korpela AT islay DOT ssl DOT berkeley DOT edu (Eric J. Korpela)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Is this ASM ok?
Date: 25 Mar 1996 19:35:33 GMT
Organization: Cal Berkeley-- Space Sciences Lab
Lines: 42
Message-ID: <4j6si5$6ak@agate.berkeley.edu>
References: <3150B8B2 DOT 8B2 AT jeffnet DOT org> <4ishog$obf AT mack DOT rt66 DOT com> <4ius89$76n AT agate DOT berkeley DOT edu> <4j4q67$h4b AT mack DOT rt66 DOT com>
NNTP-Posting-Host: islay.ssl.berkeley.edu
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

In article <4j4q67$h4b AT mack DOT rt66 DOT com>,
Brennan "Mr. Wacko" Underwood <brennan AT mack DOT rt66 DOT com> wrote:
>>>asm(
>>>  "loopf:\n\t"
>>>  "movb %%dh, (%%edi)\n\t"	/* write integer portion of color - U1 */
>>>  "addl %%ebx, %%edx\n\t"       /* Add colstep to col             - V1 */
>>>  "incl %%edi\n\t"		/* increment edi                  - U2 */
>>>  "decl %ecx\n\t"		/* decrement count                - V2 */
>>>  "jnz loopf"     	        /* If ecx not zero goto loop      - U3 */
>>>  : : "D" (tscreen), "d" (tcol1), "b" (tcolstep), "c" (tlength)/*loaded regs*/
>>>  : "%edi", "%ebx", "%ecx", "%edx"); /* clobbered regs */
>
>Oh, I see what you mean about the Info pages. That refers to this register
>loading method: "q" (tscreen) then use %0 for the register name, in case
>GCC was already using eax or whatever you would have picked. Or something
>to that effect. I haven't been able to get that to be useful yet, I just
>specify the registers.
>

That's somewhat confusing.  Are you saying that you could also have
written the above as:

asm(
  "loopf:\n\t"
  "movb %%dh, (%0)\n\t"   /* write integer portion of color - U1 */
  "addl %2, %1\n\t"       /* Add colstep to col             - V1 */
  "incl %0\n\t"           /* increment edi                  - U2 */
  "decl %3\n\t"            /* decrement count                - V2 */
  "jnz loopf"                /* If ecx not zero goto loop      - U3 */
  : : "D" (tscreen), "d" (tcol1), "b" (tcolstep), "c" (tlength)/*loaded regs*/
  );

And that in this case, gcc would know the clobbered registers because you used
the %0..%3 macros instead of the explicit names?  That's weird.  Or am I
misreading what you said?

Eric
-- 
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