[llvm-commits] [LLVMdev] [PATCH] BasicBlock Autovectorization Pass

[Hal Finkel]

I know that this is a fairly-large patch (and that everyone has been
busy), but I'm 'pinging' on the review just to make sure that it is not
overlooked. I know that I've sent a large number of revisions, but I
think that the version that I posted on 11/23 should be reviewed.

Thanks again,
Hal

On Wed, 2011-11-23 at 10:52 -0600, Hal Finkel wrote:
> On Mon, 2011-11-21 at 21:22 -0600, Hal Finkel wrote:
> > On Mon, 2011-11-21 at 11:55 -0600, Hal Finkel wrote:
> > > Tobias,
> > > 
> > > I've attached an updated patch. It contains a few bug fixes and many
> > > (refactoring and coding-convention) changes inspired by your comments.
> > > 
> > > I'm currently trying to fix the bug responsible for causing a compile
> > > failure when compiling
> > > test-suite/MultiSource/Applications/obsequi/toggle_move.c; after the
> > > pass begins to fuse instructions in a basic block in this file, the
> > > aliasing analysis starts producing different (more pessimistic) query
> > > answers. I've never before seen it do this, and I'm not sure why it is
> > > happening. Also odd, at the same time, the numeric labels that are
> > > assigned to otherwise unnamed instructions, change. I don't think I've
> > > seen this happen either (they generally seem to stay fixed once
> > > assigned). I don't know if these two things are related, but if anyone
> > > can provide some insight, I'd appreciate it.
> > 
> > I think that I see what is happening in this case (please someone tell
> > me if this does not make sense). In the problematic basic block, there
> > are some loads and stores that are independent. The default aliasing
> > analysis can tell that these loads and stores don't reference the same
> > memory region. Then, some of the inputs to the getelementptr
> > instructions used for these loads and stores are fused by the
> > vectorization. After this happens, the aliasing analysis loses its
> > ability to tell that the loads and stores that make use of those
> > vector-calculated indices are independent.
> 
> The attached patch works around this issue. Please review.
> 
> Thanks again,
> Hal
> 
> > 
> >  -Hal
> > 
> > > 
> > > In any case, this version of the patch should be much more suitable for
> > > your (or anyone else's) further review.
> > > 
> > > Thanks again,
> > > Hal
> > > 
> > > On Thu, 2011-11-17 at 13:57 +0100, Tobias Grosser wrote:
> > > > On 11/17/2011 12:38 AM, Hal Finkel wrote:
> > > > > Tobias, et al.,
> > > > >
> > > > > Attached is the my autovectorization pass.
> > > > 
> > > > Very nice. Will you be at the developer summit? Maybe we could discuss 
> > > > the integration there?
> > > > 
> > > > Here a first review of the source code.
> > > > 
> > 
> > 
> 
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-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory