[llvm] r258296 - [SelectionDAG] Fold more offsets into GlobalAddresses

[Tobias Grosser via llvm-commits]

Great. All is green again. 

On Thu, Jan 21, 2016, at 12:22 AM, Dan Gohman via llvm-commits wrote:
> Hi Tobias,
> 
> Thanks for the report! I've now submitted r258366 with a fix.
> 
> Dan
> 
> On Wed, Jan 20, 2016 at 12:13 PM, Tobias Grosser <tobias at grosser.es>
> wrote:
> 
> > On 01/20/2016 08:03 AM, Dan Gohman via llvm-commits wrote:
> >
> >> Author: djg
> >> Date: Wed Jan 20 01:03:08 2016
> >> New Revision: 258296
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=258296&view=rev
> >> Log:
> >> [SelectionDAG] Fold more offsets into GlobalAddresses
> >>
> >> SelectionDAG previously missed opportunities to fold constants into
> >> GlobalAddresses in several areas. For example, given `(add (add GA, c1),
> >> y)`, it
> >> would often reassociate to `(add (add GA, y), c1)`, missing the
> >> opportunity to
> >> create `(add GA+c, y)`. This isn't often visible on targets such as X86
> >> which
> >> effectively reassociate adds in their complex address-mode folding logic,
> >> however it is currently visible on WebAssembly since it currently has very
> >> simple address mode folding code that doesn't reassociate anything.
> >>
> >> This patch fixes this by making SelectionDAG fold offsets into
> >> GlobalAddresses
> >> at the same times that it folds constants together, so that it doesn't
> >> miss any
> >> opportunities to perform such folding.
> >>
> >
> > Hi Dan,
> >
> > I see a miscompile in LNT after this patch:
> >
> > http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3/builds/7631
> >
> > The previous build passes and the other commits seem to be in components
> > that are unlikely to even be used.
> >
> > Best,
> > Tobias
> >
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