[X86] Add two combine rules to simplify dag nodes introduced during type legalization when promoting nodes with illegal vector type.
This patch teaches the backend how to simplify/canonicalize dag node
sequences normally introduced by the backend when promoting certain dag nodes
with illegal vector type.
This patch adds two new combine rules:
1) fold (shuffle (bitcast (BINOP A, B)), Undef, <Mask>) ->
(shuffle (BINOP (bitcast A), (bitcast B)), Undef, <Mask>)
2) fold (BINOP (shuffle (A, Undef, <Mask>)), (shuffle (B, Undef, <Mask>))) ->
(shuffle (BINOP A, B), Undef, <Mask>).
Both rules are only triggered on the type-legalized DAG.
In particular, rule 1. is a target specific combine rule that attempts
to sink a bitconvert into the operands of a binary operation.
Rule 2. is a target independet rule that attempts to move a shuffle
immediately after a binary operation.
llvm-svn: 209930
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 98ae4db..6a962fd 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10801,6 +10801,27 @@
return DAG.getNode(ISD::BUILD_VECTOR, SDLoc(N), LHS.getValueType(), Ops);
}
+ // Type legalization might introduce new shuffles in the DAG.
+ // Fold (VBinOp (shuffle (A, Undef, Mask)), (shuffle (B, Undef, Mask)))
+ // -> (shuffle (VBinOp (A, B)), Undef, Mask).
+ if (LegalTypes && isa<ShuffleVectorSDNode>(LHS) &&
+ isa<ShuffleVectorSDNode>(RHS) && LHS.hasOneUse() && RHS.hasOneUse() &&
+ LHS.getOperand(1).getOpcode() == ISD::UNDEF &&
+ RHS.getOperand(1).getOpcode() == ISD::UNDEF) {
+ ShuffleVectorSDNode *SVN0 = cast<ShuffleVectorSDNode>(LHS);
+ ShuffleVectorSDNode *SVN1 = cast<ShuffleVectorSDNode>(RHS);
+
+ if (SVN0->getMask().equals(SVN1->getMask())) {
+ EVT VT = N->getValueType(0);
+ SDValue UndefVector = LHS.getOperand(1);
+ SDValue NewBinOp = DAG.getNode(N->getOpcode(), SDLoc(N), VT,
+ LHS.getOperand(0), RHS.getOperand(0));
+ AddUsersToWorkList(N);
+ return DAG.getVectorShuffle(VT, SDLoc(N), NewBinOp, UndefVector,
+ &SVN0->getMask()[0]);
+ }
+ }
+
return SDValue();
}