Fix SILParsing for forwarding ownership kind

Author: meg-gupta

docs/SIL.rst

@@ -2036,7 +2036,15 @@ and as a result:
 
 * Textual SIL does not represent the ownership of forwarding instructions
   explicitly. Instead, the instruction's ownership is inferred normally from the
-  parsed operand. Since the SILVerifier runs on Textual SIL after parsing, you
+  parsed operand.
+  In some cases the forwarding ownership kind is different from the ownership kind
+  of its operand. In such cases, textual SIL represents the forwarding ownership kind
+  explicity.
+  Eg: ::
+
+    %cast = unchecked_ref_cast %val : $Klass to $Optional<Klass>, forwarding: @unowned
+
+  Since the SILVerifier runs on Textual SIL after parsing, you
   can feel confident that ownership constraints were inferred correctly.
 
 Forwarding has slightly different ownership semantics depending on the value

include/swift/SIL/SILBuilder.h

@@ -1845,10 +1845,20 @@ class SILBuilder {
   createInitExistentialRef(SILLocation Loc, SILType ExistentialType,
                            CanType FormalConcreteType, SILValue Concrete,
                            ArrayRef<ProtocolConformanceRef> Conformances) {
+    return createInitExistentialRef(Loc, ExistentialType, FormalConcreteType,
+                                    Concrete, Conformances,
+                                    Concrete.getOwnershipKind());
+  }
+
+  InitExistentialRefInst *
+  createInitExistentialRef(SILLocation Loc, SILType ExistentialType,
+                           CanType FormalConcreteType, SILValue Concrete,
+                           ArrayRef<ProtocolConformanceRef> Conformances,
+                           ValueOwnershipKind forwardingOwnershipKind) {
     return insert(InitExistentialRefInst::create(
         getSILDebugLocation(Loc), ExistentialType, FormalConcreteType, Concrete,
         Conformances, &getFunction(), C.OpenedArchetypes,
-        Concrete.getOwnershipKind()));
+        forwardingOwnershipKind));
   }
 
   DeinitExistentialAddrInst *createDeinitExistentialAddr(SILLocation Loc,
@@ -2298,6 +2308,14 @@ class SILBuilder {
                           ProfileCounter Target1Count = ProfileCounter(),
                           ProfileCounter Target2Count = ProfileCounter());
 
+  CheckedCastBranchInst *
+  createCheckedCastBranch(SILLocation Loc, bool isExact, SILValue op,
+                          SILType destLoweredTy, CanType destFormalTy,
+                          SILBasicBlock *successBB, SILBasicBlock *failureBB,
+                          ValueOwnershipKind forwardingOwnershipKind,
+                          ProfileCounter Target1Count = ProfileCounter(),
+                          ProfileCounter Target2Count = ProfileCounter());
+
   CheckedCastValueBranchInst *
   createCheckedCastValueBranch(SILLocation Loc,
                                SILValue op, CanType srcFormalTy,

include/swift/SIL/SILCloner.h

@@ -2697,8 +2697,8 @@ SILCloner<ImplClass>::visitCheckedCastBranchInst(CheckedCastBranchInst *Inst) {
                 getOpLocation(Inst->getLoc()), Inst->isExact(),
                 getOpValue(Inst->getOperand()),
                 getOpType(Inst->getTargetLoweredType()),
-                getOpASTType(Inst->getTargetFormalType()),
-                OpSuccBB, OpFailBB, TrueCount, FalseCount));
+                getOpASTType(Inst->getTargetFormalType()), OpSuccBB, OpFailBB,
+                Inst->getForwardingOwnershipKind(), TrueCount, FalseCount));
 }
 
 template <typename ImplClass>

lib/SIL/IR/SILBuilder.cpp

@@ -656,13 +656,23 @@ CheckedCastBranchInst *SILBuilder::createCheckedCastBranch(
     SILType destLoweredTy, CanType destFormalTy,
     SILBasicBlock *successBB, SILBasicBlock *failureBB,
     ProfileCounter target1Count, ProfileCounter target2Count) {
+  return createCheckedCastBranch(Loc, isExact, op, destLoweredTy, destFormalTy,
+                                 successBB, failureBB, op.getOwnershipKind(),
+                                 target1Count, target2Count);
+}
+
+CheckedCastBranchInst *SILBuilder::createCheckedCastBranch(
+    SILLocation Loc, bool isExact, SILValue op, SILType destLoweredTy,
+    CanType destFormalTy, SILBasicBlock *successBB, SILBasicBlock *failureBB,
+    ValueOwnershipKind forwardingOwnershipKind, ProfileCounter target1Count,
+    ProfileCounter target2Count) {
   assert((!hasOwnership() || !failureBB->getNumArguments() ||
           failureBB->getArgument(0)->getType() == op->getType()) &&
          "failureBB's argument doesn't match incoming argument type");
   return insertTerminator(CheckedCastBranchInst::create(
       getSILDebugLocation(Loc), isExact, op, destLoweredTy, destFormalTy,
       successBB, failureBB, getFunction(), C.OpenedArchetypes, target1Count,
-      target2Count, op.getOwnershipKind()));
+      target2Count, forwardingOwnershipKind));
 }
 
 void SILBuilderWithScope::insertAfter(SILInstruction *inst,