Re: enabling libgcc for 64-bit divisions, was Re: PROBLEM: XFS on ARM corruption 'Structure needs cl

From: Linus Torvalds
Date: Thu Aug 13 2015 - 14:26:47 EST

On Thu, Aug 13, 2015 at 11:18 AM, George Spelvin <linux@xxxxxxxxxxx> wrote:
> On x86, the case that msword >= divsor causes a divide exception
> (divide ba generalization of divide by zero), so it's tempting
> to do the same sort of "assume no trap and fix up in the handler"
> trick as <asm/uaccess.h>.

That would be horrible. One of the reasonably common cases of do_div()
is for printing out numbers. And they are often in the 4G+ range..

> One function that would cover a significant number of use cases
> (but not all, damn it) would be
> rem = do_mul_div(x, mul,_div)

Yes. That might be worth introducing. Not to replace do_div(), but as
a "32-bit only" interface to a somewhat common situation.

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