[PATCH] [x86] Teach the X86 backend to DAG-combine SSE2 shuffles that are trivially redundant.

[Filipe Cabecinhas]

LGTM after the other patch, as well.
I just have a small comment on naming, but that basically relates to the whole file, unfortunately.

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Comment at: lib/Target/X86/X86ISelLowering.cpp:18826
@@ +18825,3 @@
+/// \brief Try to combine x86 target specific shuffles.
+static SDValue PerformTargetShuffleCombine(SDValue N, SelectionDAG &DAG,
+                                           TargetLowering::DAGCombinerInfo &DCI,
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Since we're already on the X86 backend, could we start calling these functions PerformX86ShuffleCombine? It's not like they're generic for more targets.

I know “Target” is what's being used everywhere else, but I'd prefer more specific naming.

http://reviews.llvm.org/D4240