ptx: add set.p instruction and related changes to predicate execution

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127577 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PTX/PTXAsmPrinter.cpp b/lib/Target/PTX/PTXAsmPrinter.cpp
index 8b5ed45..087d4f9 100644
--- a/lib/Target/PTX/PTXAsmPrinter.cpp
+++ b/lib/Target/PTX/PTXAsmPrinter.cpp
@@ -410,7 +410,7 @@
 
   DEBUG(dbgs() << "predicate: (" << reg << ", " << predOp << ")\n");
 
-  if (reg && predOp != PTX::PRED_IGNORE) {
+  if (reg != PTX::NoRegister) {
     O << '@';
     if (predOp == PTX::PRED_NEGATE)
       O << '!';