From 08da177c355dcde40dbe6c0a21b26956fcbca32c Mon Sep 17 00:00:00 2001 From: Stepan Dyatkovskiy Date: Mon, 20 Aug 2012 07:57:06 +0000 Subject: Fixed DAGCombiner bug (found and localized by James Malloy): The DAGCombiner tries to optimise a BUILD_VECTOR by checking if it consists purely of get_vector_elts from one or two source vectors. If so, it either makes a concat_vectors node or a shufflevector node. However, it doesn't check the element type width of the underlying vector, so if you have this sequence: Node0: v4i16 = ... Node1: i32 = extract_vector_elt Node0 Node2: i32 = extract_vector_elt Node0 Node3: v16i8 = BUILD_VECTOR Node1, Node2, ... It will attempt to: Node0: v4i16 = ... NewNode1: v16i8 = concat_vectors Node0, ... Where this is actually invalid because the element width is completely different. This causes an assertion failure on DAG legalization stage. Fix: If output item type of BUILD_VECTOR differs from input item type. Make concat_vectors based on input element type and then bitcast it to the output vector type. So the case described above will transformed to: Node0: v4i16 = ... NewNode1: v8i16 = concat_vectors Node0, ... NewNode2: v16i8 = bitcast NewNode1 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162195 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'lib') diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 4e29879..1c485a0 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -7876,9 +7876,29 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) { if (VecIn1.getValueType().getSizeInBits()*2 != VT.getSizeInBits()) return SDValue(); - // Widen the input vector by adding undef values. - VecIn1 = DAG.getNode(ISD::CONCAT_VECTORS, N->getDebugLoc(), VT, - VecIn1, DAG.getUNDEF(VecIn1.getValueType())); + // If the element type of the input vector is not the same as + // the output element type, make concat_vectors based on input element + // type and then bitcast it to the output vector type. + // + // In another words avoid nodes like this: + // v16i8 = concat_vectors v4i16 v4i16 + // Replace it with this one: + // v8i16 = concat_vectors v4i16 v4i16 + // v16i8 = bitcast NODE0 + EVT ItemType = VecIn1.getValueType().getVectorElementType(); + if (ItemType != VT.getVectorElementType()) { + EVT ConcatVT = EVT::getVectorVT(*DAG.getContext(), + ItemType, + VecIn1.getValueType().getVectorNumElements()*2); + // Widen the input vector by adding undef values. + VecIn1 = DAG.getNode(ISD::CONCAT_VECTORS, dl, ConcatVT, + VecIn1, DAG.getUNDEF(VecIn1.getValueType())); + VecIn1 = DAG.getNode(ISD::BITCAST, dl, VT, VecIn1); + } else + // Widen the input vector by adding undef values. + VecIn1 = DAG.getNode(ISD::CONCAT_VECTORS, dl, VT, + VecIn1, DAG.getUNDEF(VecIn1.getValueType())); + } // If VecIn2 is unused then change it to undef. -- cgit v1.1