sil: load [copy] affects reference counting

Based on what I see from OwnershipModelEliminator,
`%x = load [copy] %y` can turn into a plain load
followed by a retain of the loaded value.

See `NonTrivialLoadableTypeLowering::emitLoad`

Author: kavon

docs/SIL/Instructions.md

@@ -832,16 +832,16 @@ load-ownership-kind ::= 'take'
 ```
 
 Loads the value at address `%0` from memory. `T` must be a loadable
-type. This does not affect the reference count, if any, of the loaded
+type. An unqualified load does not affect the reference count, if any, of the loaded
 value; the value must be retained explicitly if necessary. It is
 undefined behavior to load from uninitialized memory or to load from an
 address that points to deallocated storage.
 
 In OSSA the ownership kind specifies how to handle ownership:
 -  **trivial**: the loaded value is trivial and no further action must be taken
                 than to load the raw bits of the value
--  **copy**: the loaded value is copied and the original value stays in the
-             memory location.
+-  **copy**: the loaded value is copied (e.g., retained) and the original value
+                stays in the memory location.
 -  **take**: the value is _moved_ from the memory location without copying.
              After the `load`, the memory location remains uninitialized.
 

lib/SIL/Utils/InstructionUtils.cpp

@@ -552,7 +552,6 @@ RuntimeEffect swift::getRuntimeEffect(SILInstruction *inst, SILType &impactType)
   case SILInstructionKind::CopyableToMoveOnlyWrapperValueInst:
   case SILInstructionKind::MoveOnlyWrapperToCopyableValueInst:
   case SILInstructionKind::UncheckedOwnershipConversionInst:
-  case SILInstructionKind::LoadInst:
   case SILInstructionKind::LoadBorrowInst:
   case SILInstructionKind::BeginBorrowInst:
   case SILInstructionKind::BorrowedFromInst:
@@ -626,6 +625,14 @@ RuntimeEffect swift::getRuntimeEffect(SILInstruction *inst, SILType &impactType)
   case SILInstructionKind::TypeValueInst:
   case SILInstructionKind::IgnoredUseInst:
     return RuntimeEffect::NoEffect;
+
+  case SILInstructionKind::LoadInst: {
+    if (cast<LoadInst>(inst)->getOwnershipQualifier() == LoadOwnershipQualifier::Copy) {
+      return ifNonTrivial(inst->getOperand(0)->getType(),
+                          RuntimeEffect::RefCounting);
+    }
+    return RuntimeEffect::NoEffect;
+  }
 
   case SILInstructionKind::OpenExistentialMetatypeInst:
   case SILInstructionKind::OpenExistentialBoxInst: