tblgen: Mechanically move dynamic_cast<> to dyn_cast<>.

Some of these dyn_cast<>'s would be better phrased as isa<> or cast<>.
That will happen in a future patch.

There are also two dyn_cast_or_null<>'s slipped in instead of
dyn_cast<>'s, since they were causing crashes with just dyn_cast<>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165646 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/InstrInfoEmitter.cpp b/utils/TableGen/InstrInfoEmitter.cpp
index 79602da..34e363d 100644
--- a/utils/TableGen/InstrInfoEmitter.cpp
+++ b/utils/TableGen/InstrInfoEmitter.cpp
@@ -89,7 +89,7 @@
       for (unsigned j = 0, e = Inst.Operands[i].MINumOperands; j != e; ++j) {
         OperandList.push_back(Inst.Operands[i]);
 
-        Record *OpR = dynamic_cast<DefInit*>(MIOI->getArg(j))->getDef();
+        Record *OpR = dyn_cast<DefInit>(MIOI->getArg(j))->getDef();
         OperandList.back().Rec = OpR;
       }
     }
@@ -345,7 +345,7 @@
   if (!TSF) throw "no TSFlags?";
   uint64_t Value = 0;
   for (unsigned i = 0, e = TSF->getNumBits(); i != e; ++i) {
-    if (BitInit *Bit = dynamic_cast<BitInit*>(TSF->getBit(i)))
+    if (BitInit *Bit = dyn_cast<BitInit>(TSF->getBit(i)))
       Value |= uint64_t(Bit->getValue()) << i;
     else
       throw "Invalid TSFlags bit in " + Inst.TheDef->getName();