Teach the DAG combiner to fold a splat of a splat. Radar 8597790.
Also do some minor refactoring to reduce indentation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117558 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 35e1f27..d09ae2d 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6346,9 +6346,10 @@
// FIXME: implement canonicalizations from DAG.getVectorShuffle()
- // If it is a splat, check if the argument vector is a build_vector with
- // all scalar elements the same.
- if (cast<ShuffleVectorSDNode>(N)->isSplat()) {
+ // If it is a splat, check if the argument vector is another splat or a
+ // build_vector with all scalar elements the same.
+ ShuffleVectorSDNode *SVN = cast<ShuffleVectorSDNode>(N);
+ if (SVN->isSplat() && SVN->getSplatIndex() < (int)NumElts) {
SDNode *V = N0.getNode();
// If this is a bit convert that changes the element type of the vector but
@@ -6361,31 +6362,34 @@
V = ConvInput.getNode();
}
+ // Fold a splat of a splat.
+ ShuffleVectorSDNode *SVV = dyn_cast<ShuffleVectorSDNode>(V);
+ if (SVV && SVV->isSplat())
+ return N0;
+
if (V->getOpcode() == ISD::BUILD_VECTOR) {
- unsigned NumElems = V->getNumOperands();
- unsigned BaseIdx = cast<ShuffleVectorSDNode>(N)->getSplatIndex();
- if (NumElems > BaseIdx) {
- SDValue Base;
- bool AllSame = true;
- for (unsigned i = 0; i != NumElems; ++i) {
- if (V->getOperand(i).getOpcode() != ISD::UNDEF) {
- Base = V->getOperand(i);
- break;
- }
+ assert(V->getNumOperands() == NumElts &&
+ "BUILD_VECTOR has wrong number of operands");
+ SDValue Base;
+ bool AllSame = true;
+ for (unsigned i = 0; i != NumElts; ++i) {
+ if (V->getOperand(i).getOpcode() != ISD::UNDEF) {
+ Base = V->getOperand(i);
+ break;
}
- // Splat of <u, u, u, u>, return <u, u, u, u>
- if (!Base.getNode())
- return N0;
- for (unsigned i = 0; i != NumElems; ++i) {
- if (V->getOperand(i) != Base) {
- AllSame = false;
- break;
- }
- }
- // Splat of <x, x, x, x>, return <x, x, x, x>
- if (AllSame)
- return N0;
}
+ // Splat of <u, u, u, u>, return <u, u, u, u>
+ if (!Base.getNode())
+ return N0;
+ for (unsigned i = 0; i != NumElts; ++i) {
+ if (V->getOperand(i) != Base) {
+ AllSame = false;
+ break;
+ }
+ }
+ // Splat of <x, x, x, x>, return <x, x, x, x>
+ if (AllSame)
+ return N0;
}
}
return SDValue();