[DAG] Check in advance if a build_vector has a legal type before attempting to convert it into a shuffle.

Currently, the DAG Combiner only tries to convert type-legal build_vector nodes
into shuffles. This patch simply moves the logic that checks if a
build_vector has a legal value type up before we even start analyzing the
operands. This allows to early exit immediately from method
'visitBUILD_VECTOR' if the node type is known to be illegal.

No functional change intended.

llvm-svn: 218677

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 2b65cce970c..aee6455713a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10423,6 +10423,10 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
   // operations.  If so, and if the EXTRACT_VECTOR_ELT vector inputs come from
   // at most two distinct vectors, turn this into a shuffle node.
 
+  // Only type-legal BUILD_VECTOR nodes are converted to shuffle nodes.
+  if (!isTypeLegal(VT))
+    return SDValue();
+
   // May only combine to shuffle after legalize if shuffle is legal.
   if (LegalOperations && !TLI.isOperationLegal(ISD::VECTOR_SHUFFLE, VT))
     return SDValue();
@@ -10514,10 +10518,6 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
         VecIn1.getValueType() != VT)
           return SDValue();
 
-    // Only type-legal BUILD_VECTOR nodes are converted to shuffle nodes.
-    if (!isTypeLegal(VT))
-      return SDValue();
-
     // Return the new VECTOR_SHUFFLE node.
     SDValue Ops[2];
     Ops[0] = VecIn1;