[llvm] r218677 - [DAG] Check in advance if a build_vector has a legal type before attempting to convert it into a shuffle.

[Andrea Di Biagio]

Author: adibiagio
Date: Tue Sep 30 10:30:22 2014
New Revision: 218677

URL: http://llvm.org/viewvc/llvm-project?rev=218677&view=rev
Log:
[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.


Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=218677&r1=218676&r2=218677&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Sep 30 10:30:22 2014
@@ -10423,6 +10423,10 @@ SDValue DAGCombiner::visitBUILD_VECTOR(S
   // 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(S
         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;