Revert the SelectionDAG optimization that makes

it impossible to create a MERGE_VALUES node with
only one result: sometimes it is useful to be able
to create a node with only one result out of one of
the results of a node with more than one result, for
example because the new node will eventually be used
to replace a one-result node using ReplaceAllUsesWith,
cf X86TargetLowering::ExpandFP_TO_SINT.  On the other
hand, most users of MERGE_VALUES don't need this and
for them the optimization was valuable.  So add a new
utility method getMergeValues for creating MERGE_VALUES
nodes which by default performs the optimization.
Change almost everywhere to use getMergeValues (and
tidy some stuff up at the same time).

llvm-svn: 52893

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 023be5c6954..6456fa30e3f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1983,8 +1983,7 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT VT, SDOperand Operand) {
   unsigned OpOpcode = Operand.Val->getOpcode();
   switch (Opcode) {
   case ISD::TokenFactor:
-  case ISD::MERGE_VALUES:
-    return Operand;         // Factor or merge of one node?  No need.
+    return Operand;         // Factor of one node?  No need.
   case ISD::FP_ROUND: assert(0 && "Invalid method to make FP_ROUND node");
   case ISD::FP_EXTEND:
     assert(VT.isFloatingPoint() &&