[OpaqueValues] Keypath setters observe triviality.

When constructing r-values during keypath setter emission, consider
whether the argument's type is trivial and construct the relevant
r-value based on that.  This worked before without opaque values because
the value is always an address.

Author: nate-chandler

lib/SILGen/SILGenExpr.cpp

@@ -3261,9 +3261,11 @@ static SILFunction *getOrCreateKeyPathSetter(SILGenModule &SGM,
   auto subscriptIndices =
     loadIndexValuesForKeyPathComponent(subSGF, loc, property,
                                        indexes, indexPtrArg);
-  
-  auto valueOrig = ManagedValue::forBorrowedRValue(valueArg)
-      .copy(subSGF, loc);
+
+  auto valueOrig = valueArgTy.isTrivial(subSGF.F)
+                       ? ManagedValue::forTrivialRValue(valueArg)
+                       : ManagedValue::forBorrowedRValue(valueArg);
+  valueOrig = valueOrig.copy(subSGF, loc);
   auto valueSubst = subSGF.emitOrigToSubstValue(loc, valueOrig,
                                                 AbstractionPattern::getOpaque(),
                                                 propertyType);

test/SILGen/opaque_values_silgen.swift

@@ -662,3 +662,19 @@ public func backDeployingReturningGeneric<T>(_ t: T) throws -> T { t }
 func set<Container, Field>(into container: inout Container, at keyPath: WritableKeyPath<Container, Field>, _ value: Field) {
   container[keyPath: keyPath] = value
 }
+
+// CHECK-LABEL: sil {{.*}}[ossa] @$s20opaque_values_silgen16FormClassKeyPathyyF1QL_C1qSivpADTk : {{.*}} {
+// CHECK:       bb0([[VALUE:%[^,]+]] :
+// CHECK-SAME:      [[CONTAINER:%[^,]+]] :
+// CHECK:         [[CONTAINER_COPY:%[^,]+]] = copy_value [[CONTAINER]]
+// CHECK:         [[SETTER:%[^,]+]] = class_method [[CONTAINER_COPY]]
+// CHECK:         [[REGISTER_4:%[^,]+]] = apply [[SETTER]]([[VALUE]], [[CONTAINER_COPY]])
+// CHECK:         destroy_value [[CONTAINER_COPY]]
+// CHECK-LABEL: } // end sil function '$s20opaque_values_silgen16FormClassKeyPathyyF1QL_C1qSivpADTk'
+@_silgen_name("FormClassKeyPath")
+func FormClassKeyPath() {
+  class Q {
+    var q: Int = 0
+  }
+  _ = \Q.q
+}