[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 0/4] tcg/optimize: fixes and improvements
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] [PATCH 0/4] tcg/optimize: fixes and improvements |
Date: |
Mon, 9 Sep 2013 19:04:31 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Sep 03, 2013 at 09:21:06AM +0200, Paolo Bonzini wrote:
> Il 03/09/2013 08:27, Aurelien Jarno ha scritto:
> > This patchset first fixes known-zero bits optimization so that it is
> > actually used, and does some further optimizations for 32-bit ops and
> > unsigned loads.
> >
> > Aurelien Jarno (4):
> > tcg/optimize: fix know-zero bits optimization
> > tcg/optimize: fix known-zero bits for right shift ops
> > tcg/optimize: improve known-zero bits for 32-bit ops
> > tcg/optimize: add known-zero bits compute for load ops
> >
> > tcg/optimize.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 43 insertions(+), 5 deletions(-)
> >
>
> Commit message 1 is a bit misleading, because the optimization still
> works for quite a few cases involving constant and copy propagation.
> However, I had the same patch in my queue, so I can't deny that there is
> a problem. :)
I have just checked, and it does indeed work for a few cases involving
constants. That said, it doesn't change the resulting TCG code, as these
cases were already handled by some other optimizations.
That let me ask a question, about why the bit propagation has been added
in the middle of other optimizations, and not for example immediately
after swapping commutative ops or just before the constant folding.
> Two questions:
>
> 1) should patch 2 be CCed to qemu-stable?
I considered it was not a problem given I thought the optimization was
basically disabled. I'll fix that in the new version.
> 2) should patches 1 and 2 be inverted to avoid triggering bugs?
Good idea.
Thanks for the review, I'll send an updated version.
--
Aurelien Jarno GPG: 1024D/F1BCDB73
address@hidden http://www.aurel32.net
- [Qemu-devel] [PATCH 0/4] tcg/optimize: fixes and improvements, Aurelien Jarno, 2013/09/03
- [Qemu-devel] [PATCH 2/4] tcg/optimize: fix known-zero bits for right shift ops, Aurelien Jarno, 2013/09/03
- [Qemu-devel] [PATCH 4/4] tcg/optimize: add known-zero bits compute for load ops, Aurelien Jarno, 2013/09/03
- [Qemu-devel] [PATCH 1/4] tcg/optimize: fix know-zero bits optimization, Aurelien Jarno, 2013/09/03
- [Qemu-devel] [PATCH 3/4] tcg/optimize: improve known-zero bits for 32-bit ops, Aurelien Jarno, 2013/09/03
- Re: [Qemu-devel] [PATCH 0/4] tcg/optimize: fixes and improvements, Paolo Bonzini, 2013/09/03
- Re: [Qemu-devel] [PATCH 0/4] tcg/optimize: fixes and improvements,
Aurelien Jarno <=
- Re: [Qemu-devel] [PATCH 0/4] tcg/optimize: fixes and improvements, Richard Henderson, 2013/09/03