[dart2js] Remove receiver-not-null strengthening
Adding the inference that, after `x.foo()`, `x` cannot be null used to
make sense, but with sound null safety means this is only applicable
when `x` is `dynamic`.
Removing the `knownType` update logic makes it easier to reason about
type propagation. There are very few regressions for removing this now
(huge app had half a dozen minor regressions, several other apps had
none).
If we decide to add something like this in the future, I think it
should be added as part of SsaTypeConversionInserter, and be extended
to add other post-conditions (e.g. the runtime helper `checkString(s)`
ensures `s` is a String).
Change-Id: I27a7fcbc13873867713c439c062ecf9bd71d644d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420504
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Mayank Patke <fishythefish@google.com>
diff --git a/pkg/compiler/lib/src/ssa/nodes.dart b/pkg/compiler/lib/src/ssa/nodes.dart
index 9fd434a..73b287d 100644
--- a/pkg/compiler/lib/src/ssa/nodes.dart
+++ b/pkg/compiler/lib/src/ssa/nodes.dart
@@ -4045,7 +4045,7 @@
/// The [HTypeKnown] instruction marks a value with a refined type.
class HTypeKnown extends HCheck {
- AbstractValue knownType;
+ final AbstractValue knownType;
final bool _isMovable;
HTypeKnown.pinned(this.knownType, HInstruction input)
diff --git a/pkg/compiler/lib/src/ssa/types_propagation.dart b/pkg/compiler/lib/src/ssa/types_propagation.dart
index cae0ea8..09c1f5f 100644
--- a/pkg/compiler/lib/src/ssa/types_propagation.dart
+++ b/pkg/compiler/lib/src/ssa/types_propagation.dart
@@ -441,40 +441,6 @@
AbstractValue receiverType = receiver.instructionType;
node.updateReceiverType(abstractValueDomain, receiverType);
- // Try to refine that the receiver is not null after this call by inserting
- // a refinement node (HTypeKnown).
- var selector = node.selector;
- if (!selector.isMaybeClosureCall && !selector.appliesToNullWithoutThrow()) {
- var next = node.next;
- if (next is HTypeKnown && next.checkedInput == receiver) {
- // On a previous pass or iteration we already refined [receiver] by
- // inserting a [HTypeKnown] instruction. That replaced several dominated
- // uses with the refinement. We update the type of the [HTypeKnown]
- // instruction because it may have been refined with a correct type at
- // the time, but incorrect now.
- AbstractValue newType = abstractValueDomain.excludeNull(receiverType);
- if (next.instructionType != newType) {
- next.knownType = next.instructionType = newType;
- addDependentInstructionsToWorkList(next);
- }
- } else if (abstractValueDomain.isNull(receiverType).isPotentiallyTrue) {
- DominatedUses uses = DominatedUses.of(
- receiver,
- node,
- excludeDominator: true,
- );
- if (uses.isNotEmpty) {
- // Insert a refinement node after the call and update all users
- // dominated by the call to use that node instead of [receiver].
- AbstractValue newType = abstractValueDomain.excludeNull(receiverType);
- HTypeKnown converted = HTypeKnown.witnessed(newType, receiver, node);
- node.block!.addBefore(node.next, converted);
- uses.replaceWith(converted);
- addDependentInstructionsToWorkList(converted);
- }
- }
- }
-
var result = node.specializer.computeTypeFromInputTypes(
node,
results,
