The AST-to-IR conversion stage now handles null-shorting property
accesses (both for reads and writes). This required adding the
following instruction types: `eq`, `block`, and `brIf`.
In order to make `eq` easier to test, support was also added for
AST-to-IR conversion of testing binary expressions using `==`.
The way null shorting is encoded in the IR is by issuing a `block`
instruction when null shorting starts, and an `end` instruction when
it terminates. Anywhere a null check appears within the null shorting
expression, the null check uses a `brIf(0)` instruction to branch to
the `end` in the case a `null` is found. To make it easier to keep
track of when `block` and `end` instructions need to be generated,
`RawIRWriter` keeps track of a count of the current nesting of control
flow contsructs.
In order for the interpreter to find to the appropriate `end`
instruction when a branch is taken, a new scope analyzer is
added. Later CLs will expand on it and use it for static analysis as
well.
Change-Id: I09ca34eaa900d47f7a4014cbc8db2a48a1d69e1e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/336800
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Paul Berry
deebb52c2b