On 07-Jan-02 Stephen Montgomery-Smith wrote: > John Baldwin wrote: >> >> > You know, I have no idea. It is someone elses code. These are the >> > instructions. Can anyone tell me? >> > >> > "movl 32(%0),%1\n" >> > "adcl %1,32(%0)\n" >> > >> > Also, from this discussion, what I have decided to do is provide it as >> > an option for the user to add by editing the Makefile - not to do it >> > automatically. >> >> These instructions are 386 instructions. What we need to see are the >> contraints (the stuff after the actual instructions with colons in them) to >> see >> if it is somehow using Pentium Pro+ specific registers. And actually, just >> for >> the record, a PPro is a 686. :) >> > > OK, this is it in context: > > register Word32 *_x = x; > register int _a = 0; > > asm("xorl %1,%1\n" /* clear C */ > "movl 124(%0),%1\n" > "adcl %1,124(%0)\n" > : : "r" (_x), "r" (_a) > );
Looks like rather silly code to double the value at x + 124. I say silly casue it clears carry and then does a addcl. However, since CF is zero, this is the same as doing an addl. Since it is just doubling the value, a shl would make more sense (and only be 1 instruction.) -- John Baldwin <[EMAIL PROTECTED]> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message