Messages in this thread | | | Date | Tue, 13 Jul 1999 15:32:57 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: 64 bit arithmetic in the kernel |
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On Tue, 13 Jul 1999, Jamie Lokier wrote:
> Michael Richardson wrote: > > Is there any easy way to get things like the stuff that it > > is in libgcc1.a into the Linux kernel? I have need for 64/32 integer divide > > (gcc calls __udivdi3). > > This is with 2.2.10, on a Lintel box, and I'm using a module. > > Richard Johnson wrote: > > Use inline asm. In Intel, you put the high long-word into edx, the low > > long-word into eax, and "div" either by an immediate or something in, say > > the ecx register. The result is a long-word in eax, with the remainder > > in edx. > > > > This results in an unsigned integer divide, which is what the __udivxxx > > means. > > Actually __udivdi3 is a 64/64 -> 64 divide, while the "div" instruction > is 64/32 -> 32. Apples and pears. > > -- Jamie >
It depends upon your C runtime library. Version 2.8.1 substitutes the 64/64 version.
This is from libgcc2.c, line 709.
#ifdef L_udivdi3 UDItype __udivmoddi4 (); UDItype __udivdi3 (UDItype n, UDItype d) { return __udivmoddi4 (n, d, (UDItype *) 0); }
We are both correct.
Cheers, Dick Johnson FILE SYSTEM MODIFIED Penguin : Linux version 2.2.6 on an i686 machine (400.59 BogoMips). Warning : It's hard to remain at the trailing edge of technology.
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