[sil] Tighten up SIL verification around when checked_cast_br should/shouldn't have failure arguments.

checked_cast_br in ownership SIL funnels through the original value to the
failure block as a SILArgument for cleanup purposes. In contrast, when SIL is
not in ossa, we do not want the failure bb case to have any arguments since that
is the pattern that SILOptimizer passes expect.

This commit just formalizes these constraints into the SILVerifier to catch
mistakes.

Author: gottesmm

lib/SIL/SILVerifier.cpp

@@ -3381,20 +3381,17 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
                 CBI->getCastType(),
             "success dest block argument of checked_cast_br must match type of "
             "cast");
-    require(F.hasOwnership() || CBI->getFailureBB()->args_empty(),
-            "failure dest of checked_cast_br in unqualified ownership sil must "
-            "take no arguments");
-#if 0
-    require(F.hasUnqualifiedOwnership() ||
-                CBI->getFailureBB()->args_size() == 1,
+    require(!F.hasOwnership() || CBI->getFailureBB()->args_size() == 1,
             "failure dest of checked_cast_br must take one argument in "
             "ownership qualified sil");
-    require(F.hasUnqualifiedOwnership() ||
+    require(!F.hasOwnership() ||
                 CBI->getFailureBB()->args_begin()[0]->getType() ==
                     CBI->getOperand()->getType(),
             "failure dest block argument must match type of original type in "
             "ownership qualified sil");
-#endif
+    require(F.hasOwnership() || CBI->getFailureBB()->args_empty(),
+            "Failure dest of checked_cast_br must not take any argument in "
+            "non-ownership qualified sil");
   }
 
   void checkCheckedCastValueBranchInst(CheckedCastValueBranchInst *CBI) {