Emit unenforced access markers in SILGen for accesses to local temporaries.

These accesses can't be recognized as obviously local temporaries in the
verification pass, so the only way to exhaustively verify exclusivity is by
added unenforced markers.

SILGen currently only emits unenforced markers under -verify-exlcusivity. Once
opaque values is the only supported SILGen mode, then we should turn the markers
on by default (SILGen should not have different modes of operation).

lib/SILGen/SILGenPattern.cpp

@@ -14,6 +14,7 @@
 #include "Cleanup.h"
 #include "ExitableFullExpr.h"
 #include "Initialization.h"
+#include "LValue.h"
 #include "RValue.h"
 #include "SILGen.h"
 #include "Scope.h"
@@ -2156,9 +2157,13 @@ void PatternMatchEmission::emitEnumElementDispatch(
         SILValue boxedValue = SGF.B.createProjectBox(loc, origCMV.getValue(), 0);
         eltTL = &SGF.getTypeLowering(boxedValue->getType());
         if (eltTL->isLoadable()) {
+          UnenforcedAccess access;
+          SILValue accessAddress =
+            access.beginAccess(SGF, loc, boxedValue, SILAccessKind::Read);
           ManagedValue newLoadedBoxValue = SGF.B.createLoadBorrow(
-              loc, ManagedValue::forUnmanaged(boxedValue));
+            loc, ManagedValue::forUnmanaged(accessAddress));
           boxedValue = newLoadedBoxValue.getUnmanagedValue();
+          access.endAccess(SGF);
         }
 
         // The boxed value may be shared, so we always have to copy it.