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Teach DAGCombiner how to fold a SIGN_EXTEND_INREG of a BUILD_VECTOR of

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ConstantSDNodes (or UNDEFs) into a simple BUILD_VECTOR.

For example, given the following sequence of dag nodes:

  i32 C = Constant<1>
  v4i32 V = BUILD_VECTOR C, C, C, C
  v4i32 Result = SIGN_EXTEND_INREG V, ValueType:v4i1

The SIGN_EXTEND_INREG node can be folded into a build_vector since
the vector in input is a BUILD_VECTOR of constants.

The optimized sequence is:

  i32 C = Constant<-1>
  v4i32 Result = BUILD_VECTOR C, C, C, C



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198084 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrea Di Biagio
2013-12-27 20:20:28 +00:00
parent bd75475bfc
commit b2f47c6a34
7 changed files with 202 additions and 17 deletions
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4
include/llvm/CodeGen/SelectionDAGNodes.h
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@ -70,6 +70,10 @@ namespace ISD {
/// BUILD_VECTOR where all of the elements are 0 or undef.
bool isBuildVectorAllZeros(const SDNode *N);
/// \brief Return true if the specified node is a BUILD_VECTOR node of
/// all ConstantSDNode or undef.
bool isBuildVectorOfConstantSDNodes(const SDNode *N);
/// isScalarToVector - Return true if the specified node is a
/// ISD::SCALAR_TO_VECTOR node or a BUILD_VECTOR node where only the low
/// element is not an undef.