HInstanceEnvironment returns the type of an instance, which gives access to all
type variables of the supertypes. HInstanceEnvironment is currently lowered to a
call to 'instanceType', but we expect to lower to a field access in
most cases, or a constant type which can be folded into subsequent operations.
The type_builder builds a type environment for each type expression. The
environment is build from the instance type scope and the function type scopes.
GVN optimizations already introduce more sharing, but it might be advantageous to
pre-compute the environment and sink the operations instead.
Later we will pass multiple type arguments as tuples which will reduce the number
of operations, especially in factory constructors.
There are some tweaks removing types in rti.dart to avoid re-entrant code.
Change-Id: I004adf7a8a464e575b32d59476c888db46542fde
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/107460
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Mayank Patke <fishythefish@google.com>
Stephen Adams
f5892dafe6