Teach the DAGCombiner how to fold concat_vector nodes when the input is two
BUILD_VECTOR nodes, e.g.:
(concat_vectors (BUILD_VECTOR a1, a2, a3, a4), (BUILD_VECTOR b1, b2, b3, b4))
->
(BUILD_VECTOR a1, a2, a3, a4, b1, b2, b3, b4)
This fixes an issue with AVX, where a sequence was not recognized as a 256-bit
vbroadcast due to the concat_vectors.
llvm-svn: 201158
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 9b84e4d..de8fbc9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10136,6 +10136,26 @@
}
}
+ // fold (concat_vectors (BUILD_VECTOR A, B, ...), (BUILD_VECTOR C, D, ...))
+ // -> (BUILD_VECTOR A, B, ..., C, D, ...)
+ if (N->getNumOperands() == 2 &&
+ N->getOperand(0).getOpcode() == ISD::BUILD_VECTOR &&
+ N->getOperand(1).getOpcode() == ISD::BUILD_VECTOR) {
+ EVT VT = N->getValueType(0);
+ SDValue N0 = N->getOperand(0);
+ SDValue N1 = N->getOperand(1);
+ SmallVector<SDValue, 8> Opnds;
+ unsigned BuildVecNumElts = N0.getNumOperands();
+
+ for (unsigned i = 0; i != BuildVecNumElts; ++i)
+ Opnds.push_back(N0.getOperand(i));
+ for (unsigned i = 0; i != BuildVecNumElts; ++i)
+ Opnds.push_back(N1.getOperand(i));
+
+ return DAG.getNode(ISD::BUILD_VECTOR, SDLoc(N), VT, &Opnds[0],
+ Opnds.size());
+ }
+
// Type legalization of vectors and DAG canonicalization of SHUFFLE_VECTOR
// nodes often generate nop CONCAT_VECTOR nodes.
// Scan the CONCAT_VECTOR operands and look for a CONCAT operations that