Fix a tblgen problem handling variable_ops in tblgen instruction

definitions. This adds a new construct, "discard", for indicating
that a named node in the input matching pattern is to be discarded,
instead of corresponding to a node in the output pattern. This
allows tblgen to know where the arguments for the varaible_ops are
supposed to begin.

This fixes "rdar://5791600", whatever that is ;-).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51699 91177308-0d34-0410-b5e6-96231b3b80d8

utils/TableGen/CodeGenInstruction.cpp

@@ -163,7 +163,8 @@ CodeGenInstruction::CodeGenInstruction(Record *R, const std::string &AsmStr)
       isVariadic = true;
       continue;
     } else if (!Rec->isSubClassOf("RegisterClass") && 
-               Rec->getName() != "ptr_rc" && Rec->getName() != "unknown")
+               Rec->getName() != "ptr_rc" && Rec->getName() != "unknown" &&
+               Rec->getName() != "discard")
       throw "Unknown operand class '" + Rec->getName() +
             "' in instruction '" + R->getName() + "' instruction!";