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Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end()
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end() |
Date: |
Sun, 16 Oct 2011 22:40:11 +1100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sun, Oct 16, 2011 at 11:56:03AM +0200, Avi Kivity wrote:
> On 10/12/2011 04:37 AM, David Gibson wrote:
[snip]
> > static AddrRange addrrange_intersection(AddrRange r1, AddrRange r2)
> > {
> > - int64_t start = MAX(r1.start, r2.start);
> > - /* off-by-one arithmetic to prevent overflow */
> > - int64_t end = MIN(addrrange_end(r1) - 1, addrrange_end(r2) - 1);
> > - return addrrange_make(start, end - start + 1);
> > + if (r1.start <= r2.start) {
> > + return addrrange_make(r2.start,
> > + MIN(r2.size, r1.size - (r2.start -
> > r1.start)));
> > + } else {
> > + return addrrange_make(r1.start,
> > + MIN(r1.size, r2.size - (r1.start -
> > r2.start)));
> > + }
> > }
> >
>
> This is pretty ugly.
A little, but it's correct...
> > struct CoalescedMemoryRange {
> > @@ -201,7 +202,8 @@ static void flatview_destroy(FlatView *view)
> >
> > static bool can_merge(FlatRange *r1, FlatRange *r2)
> > {
> > - return addrrange_end(r1->addr) == r2->addr.start
> > + assert (r1->addr.start < r2->addr.start);
>
> So is this, to a lesser extent.
Well, the assert is optional; I basically just put that in to document
the assumptions going into this function.
> Let me see if I can work up a synthetic int128 type.
So.. you think replacing every single basic arithmetic operations with
calls to implement the synthetic type, _and_ imposing the resulting
overhead is _less_ ugly than some slightly fiddly re-ordering of
operations? Seriously?
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
- [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), David Gibson, 2011/10/11
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), Avi Kivity, 2011/10/16
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(),
David Gibson <=
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), Avi Kivity, 2011/10/16
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), David Gibson, 2011/10/17
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), Avi Kivity, 2011/10/17
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), David Gibson, 2011/10/17
- Re: [Qemu-devel] [PATCH] Memory API bugfix - abolish addrrrange_end(), Avi Kivity, 2011/10/18