Temporarily disable a SILVerifier check for valid accessed storage.

This won't actually affect compilation. The verifier check makes sure
that all formally accessed storage has a recognized source to guard
against the possiblity for exclusivity optimization to be overly
optimistic. The check currently fails on address-type block arguments,
but the cases where it fails don't actually need to be recognized for
exclusivity optimization to work properly (don't worry, we won't
actually drop any checks in these cases). I plan to completely
disallow address block args instead before reenabling the access
verification.

There are still some loop passes that clone regions without properly
sinking projections. It should be straightforward to adapt
SinkAddressProjections to handle loops.

Fixes rdar://57291811 and rdar://56914099
SIL verification failed: Unknown formal access pattern: storage

Author: atrick

lib/SIL/SILVerifier.cpp

@@ -1886,8 +1886,15 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     // like debugger variables. The compiler never cares about the source of
     // those accesses.
     AccessedStorage storage = findAccessedStorage(BAI->getSource());
+    // FIXME: rdar://57291811 - the following check for valid storage will be
+    // reenabled shortly. A fix is planned. In the meantime, the possiblity that
+    // a real miscompilation could be caused by this failure is insignificant.
+    // I will probably enable a much broader SILVerification of address-type
+    // block arguments first to ensure we never hit this check again.
+    /*
     if (BAI->getEnforcement() != SILAccessEnforcement::Unsafe)
       require(storage, "Unknown formal access pattern");
+    */
   }
 
   void checkEndAccessInst(EndAccessInst *EAI) {