add an optimized form of OPC_EmitMergeInputChains for the 1, 0 and 
1, 1 cases which are by-far the most frequent.  This shrinks the X86
isel table from 77014 -> 74657 bytes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99740 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/DAGISelMatcherEmitter.cpp b/utils/TableGen/DAGISelMatcherEmitter.cpp
index 8855034..25b7a2f 100644
--- a/utils/TableGen/DAGISelMatcherEmitter.cpp
+++ b/utils/TableGen/DAGISelMatcherEmitter.cpp
@@ -449,6 +449,13 @@
   case Matcher::EmitMergeInputChains: {
     const EmitMergeInputChainsMatcher *MN =
       cast<EmitMergeInputChainsMatcher>(N);
+    
+    // Handle the specialized forms OPC_EmitMergeInputChains1_0 and 1_1.
+    if (MN->getNumNodes() == 1 && MN->getNode(0) < 2) {
+      OS << "OPC_EmitMergeInputChains1_" << MN->getNode(0) << ",\n";
+      return 1;
+    }
+    
     OS << "OPC_EmitMergeInputChains, " << MN->getNumNodes() << ", ";
     for (unsigned i = 0, e = MN->getNumNodes(); i != e; ++i)
       OS << MN->getNode(i) << ", ";