[AArch64] Add command-line option predres

Prediction control instructions are only
mandatory from v8.5a onwards but is optional
from Armv8.0-A. This patch adds a command
line option to enable it by it's own.

Differential Revision: https://reviews.llvm.org/D56007

llvm-svn: 350385
diff --git a/llvm/unittests/Support/TargetParserTest.cpp b/llvm/unittests/Support/TargetParserTest.cpp
index 3676dee..28e995e 100644
--- a/llvm/unittests/Support/TargetParserTest.cpp
+++ b/llvm/unittests/Support/TargetParserTest.cpp
@@ -990,7 +990,9 @@
                               {"rng", "norng", "+rand", "-rand"},
                               {"memtag", "nomemtag", "+mte", "-mte"},
                               {"ssbs", "nossbs", "+ssbs", "-ssbs"},
-                              {"sb", "nosb", "+sb", "-sb"}};
+                              {"sb", "nosb", "+sb", "-sb"},
+                              {"predres", "nopredres", "+predres", "-predres"}
+};
 
   for (unsigned i = 0; i < array_lengthof(ArchExt); i++) {
     EXPECT_EQ(StringRef(ArchExt[i][2]),