Andrea Di Biagio 3996e5290a [DAG] Further improve the logic in DAGCombiner that folds a pair of shuffles into a single shuffle if the resulting mask is legal. ...

This patch teaches the DAGCombiner how to fold shuffles according to the
following new rules:
  1. shuffle(shuffle(x, y), undef) -> x
  2. shuffle(shuffle(x, y), undef) -> y
  3. shuffle(shuffle(x, y), undef) -> shuffle(x, undef)
  4. shuffle(shuffle(x, y), undef) -> shuffle(y, undef)

The backend avoids to combine shuffles according to rules 3. and 4. if
the resulting shuffle does not have a legal mask. This is to avoid introducing
illegal shuffles that are potentially expanded into a sub-optimal sequence of
target specific dag nodes during vector legalization.

Added test case combine-vec-shuffle-2.ll to verify that we correctly triggers
the new rules when combining shuffles.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212748 91177308-0d34-0410-b5e6-96231b3b80d8

2014-07-10 18:04:55 +00:00

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CMakeLists.txt

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DAGCombiner.cpp

[DAG] Further improve the logic in DAGCombiner that folds a pair of shuffles into a single shuffle if the resulting mask is legal.

2014-07-10 18:04:55 +00:00

FastISel.cpp

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FunctionLoweringInfo.cpp

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InstrEmitter.cpp

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InstrEmitter.h

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LegalizeDAG.cpp

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LegalizeFloatTypes.cpp

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LegalizeIntegerTypes.cpp

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LegalizeTypes.cpp

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LegalizeTypes.h

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LegalizeTypesGeneric.cpp

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LegalizeVectorOps.cpp

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LegalizeVectorTypes.cpp

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LLVMBuild.txt

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Makefile

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ResourcePriorityQueue.cpp

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ScheduleDAGFast.cpp

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ScheduleDAGRRList.cpp

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ScheduleDAGSDNodes.cpp

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ScheduleDAGSDNodes.h

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ScheduleDAGVLIW.cpp

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SDNodeDbgValue.h

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SelectionDAG.cpp

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SelectionDAGBuilder.cpp

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SelectionDAGBuilder.h

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SelectionDAGDumper.cpp

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SelectionDAGISel.cpp

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SelectionDAGPrinter.cpp

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TargetLowering.cpp

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TargetSelectionDAGInfo.cpp

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