Remove unchecked_ownership_conversion from borrow accessor silgen

Author: meg-gupta

lib/SILGen/SILGenApply.cpp

@@ -5479,12 +5479,6 @@ ManagedValue SILGenFunction::applyBorrowMutateAccessor(
   assert(rawResults.size() == 1);
   auto rawResult = rawResults[0];
 
-  if (fn.getFunction()->getConventions().hasGuaranteedResult()) {
-    auto selfArg = args.back().getValue();
-    if (isa<LoadBorrowInst>(selfArg)) {
-      rawResult = emitUncheckedGuaranteedConversion(rawResult);
-    }
-  }
   if (rawResult->getType().isMoveOnly()) {
     if (rawResult->getType().isAddress()) {
       auto result = B.createMarkUnresolvedNonCopyableValueInst(

lib/SILGen/SILGenFunction.h

@@ -2276,8 +2276,6 @@ class LLVM_LIBRARY_VISIBILITY SILGenFunction
   emitBorrowOrMutateAccessorResult(SILLocation loc, Expr *ret,
                                    SmallVectorImpl<SILValue> &directResults);
 
-  SILValue emitUncheckedGuaranteedConversion(SILValue value);
-
   void emitYield(SILLocation loc, MutableArrayRef<ArgumentSource> yieldValues,
                  ArrayRef<AbstractionPattern> origTypes,
                  JumpDest unwindDest);

lib/SILGen/SILGenStmt.cpp

@@ -708,21 +708,6 @@ static Expr *lookThroughProjections(Expr *expr) {
   return lookThroughProjections(lookupExpr->getBase());
 }
 
-SILValue SILGenFunction::emitUncheckedGuaranteedConversion(SILValue value) {
-  assert(value->getType().isObject());
-  assert(F.getConventions().hasGuaranteedResult());
-  auto regularLoc = RegularLocation::getAutoGeneratedLocation();
-  // Introduce a pair of unchecked_ownership_conversion instructions to
-  // avoid ownership errors from returning a load borrowed value.
-  // TODO: Introduce new SIL semantics to allow returning borrowed
-  // values from within a local borrow scope.
-  auto result = B.createUncheckedOwnershipConversion(regularLoc, value,
-                                                     OwnershipKind::Unowned);
-  result = B.createUncheckedOwnershipConversion(regularLoc, result,
-                                                OwnershipKind::Guaranteed);
-  return result;
-}
-
 bool SILGenFunction::emitBorrowOrMutateAccessorResult(
     SILLocation loc, Expr *ret, SmallVectorImpl<SILValue> &directResults) {
   auto *afd = cast<AbstractFunctionDecl>(FunctionDC->getAsDecl());
@@ -734,9 +719,7 @@ bool SILGenFunction::emitBorrowOrMutateAccessorResult(
     assert(guaranteedAddress.getValue()->getType().isAddress());
     assert(F.getConventions().hasGuaranteedResult());
     auto regularLoc = RegularLocation::getAutoGeneratedLocation();
-    auto load =
-        B.createLoadBorrow(regularLoc, guaranteedAddress).getValue();
-    return emitUncheckedGuaranteedConversion(load);
+    return B.createLoadBorrow(regularLoc, guaranteedAddress).getValue();
   };
 
   // If the return expression is a literal, emit as a regular return
@@ -853,7 +836,7 @@ bool SILGenFunction::emitBorrowOrMutateAccessorResult(
     // unnecessary copy_value + mark_unresolved_non_copyable_value
     // instructions.
     if (selfType.isMoveOnly()) {
-    result = lookThroughMoveOnlyCheckerPattern(result);
+      result = lookThroughMoveOnlyCheckerPattern(result);
     }
     // If the SIL convention is @guaranteed and the generated result is an
     // address, emit a load_borrow.