Add a DAGCombine for subvector extracts to remove useless chains of
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
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c47dd09..1b73b07 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -216,6 +216,7 @@
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 @@
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 @@
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();