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 aurel...@aurel32.net http://www.aurel32.net
