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

[Hal Finkel]

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.
> > > 
> 
> 

-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory
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