diff options
Diffstat (limited to 'src/passes/OptimizeInstructions.cpp')
| -rw-r--r-- | src/passes/OptimizeInstructions.cpp | 42 |
1 files changed, 21 insertions, 21 deletions
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp index 097e0299a..e61373711 100644 --- a/src/passes/OptimizeInstructions.cpp +++ b/src/passes/OptimizeInstructions.cpp @@ -1872,28 +1872,28 @@ struct OptimizeInstructions auto intendedType = curr->type.getHeapType(); - // If the value is a null, it will just flow through, and we do not need - // the cast. However, if that would change the type, then things are less - // simple: if the original type was non-nullable, replacing it with a null - // would change the type, which can happen in e.g. - // (ref.cast (ref.as_non_null (.. (ref.null) + // If the value is a null, then we know a nullable cast will succeed and a + // non-nullable cast will fail. Either way, we do not need the cast. + // However, we have to avoid changing the type when replacing a cast with + // its potentially more refined child, e.g. + // (ref.cast null (ref.as_non_null (.. (ref.null))) if (fallthrough->is<RefNull>()) { - // Replace the expression with drops of the inputs, and a null. Note - // that we provide a null of the previous type, so that we do not alter - // the type received by our parent. - Expression* rep = builder.makeSequence(builder.makeDrop(curr->ref), - builder.makeRefNull(intendedType)); - if (curr->ref->type.isNonNullable()) { - // Avoid a type change by forcing to be non-nullable. In practice, - // this would have trapped before we get here, so this is just for - // validation. - rep = builder.makeRefAs(RefAsNonNull, rep); - } - replaceCurrent(rep); - return; - // TODO: The optimal ordering of this and the other ref.as_non_null - // stuff later down in this functions is unclear and may be worth - // looking into. + if (curr->type.isNullable()) { + // Replace the expression to drop the input and directly produce the + // null. + replaceCurrent(builder.makeSequence(builder.makeDrop(curr->ref), + builder.makeRefNull(intendedType))); + return; + // TODO: The optimal ordering of this and the other ref.as_non_null + // stuff later down in this functions is unclear and may be worth + // looking into. + } else { + // The cast will trap on the null, so replace it with an unreachable + // wrapped in a block of the original type. + replaceCurrent(builder.makeSequence( + builder.makeDrop(curr->ref), builder.makeUnreachable(), curr->type)); + return; + } } // For the cast to be able to succeed, the value being cast must be a |