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Add a DAGCombine for subvector extracts to remove useless chains of

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subvector inserts and extracts. Initial patch by Rackover, Zvi with
some tweak done by me.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140204 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bruno Cardoso Lopes
2011-09-20 23:19:33 +00:00
parent f4b841d4e2
commit e97190fdf8
2 changed files with 51 additions and 0 deletions
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32
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@@ -216,6 +216,7 @@ namespace {
SDValue visitEXTRACT_VECTOR_ELT(SDNode *N);
SDValue visitBUILD_VECTOR(SDNode *N);
SDValue visitCONCAT_VECTORS(SDNode *N);
SDValue visitEXTRACT_SUBVECTOR(SDNode *N);
SDValue visitVECTOR_SHUFFLE(SDNode *N);
SDValue visitMEMBARRIER(SDNode *N);
@@ -1105,6 +1106,7 @@ SDValue DAGCombiner::visit(SDNode *N) {
case ISD::EXTRACT_VECTOR_ELT: return visitEXTRACT_VECTOR_ELT(N);
case ISD::BUILD_VECTOR: return visitBUILD_VECTOR(N);
case ISD::CONCAT_VECTORS: return visitCONCAT_VECTORS(N);
case ISD::EXTRACT_SUBVECTOR: return visitEXTRACT_SUBVECTOR(N);
case ISD::VECTOR_SHUFFLE: return visitVECTOR_SHUFFLE(N);
case ISD::MEMBARRIER: return visitMEMBARRIER(N);
}
@@ -7031,6 +7033,36 @@ SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
return SDValue();
}
SDValue DAGCombiner::visitEXTRACT_SUBVECTOR(SDNode* N) {
EVT NVT = N->getValueType(0);
SDValue V = N->getOperand(0);
if (V->getOpcode() == ISD::INSERT_SUBVECTOR) {
// Handle only simple case where vector being inserted and vector
// being extracted are of same type, and are half size of larger vectors.
EVT BigVT = V->getOperand(0).getValueType();
EVT SmallVT = V->getOperand(1).getValueType();
if (NVT != SmallVT || NVT.getSizeInBits()*2 != BigVT.getSizeInBits())
return SDValue();
// Combine:
// (extract_subvec (insert_subvec V1, V2, InsIdx), ExtIdx)
// Into:
// indicies are equal => V1
// otherwise => (extract_subvec V1, ExtIdx)
//
SDValue InsIdx = N->getOperand(1);
SDValue ExtIdx = V->getOperand(2);
if (InsIdx == ExtIdx)
return V->getOperand(1);
return DAG.getNode(ISD::EXTRACT_SUBVECTOR, N->getDebugLoc(), NVT,
V->getOperand(0), N->getOperand(1));
}
return SDValue();
}
SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
EVT VT = N->getValueType(0);
unsigned NumElts = VT.getVectorNumElements();