Implement ConstReference optimization
#109
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added 5 commits
March 22, 2016 15:05
A const reference cannot change, so we do not need to emit an updating
opcode for them.
For example:
```has
{{#if true}}...{{/if}}
```
In this case, the conditional is a literal, so it is impossible for the
the {{#if}} to flip from default to inverse on the update pass, hence
there is no need to emit an `Assert` for the conditional value.
While this in itself is pretty rare, it is quite common for this to
happen indirectly. For example:
```hbs
{{!-- link-to component layout --}}
<a href="{{@url}}" title={{@title}}>{{@text}}</a>
```
```hbs
{{!-- link-to usage --}}
{{link-to url="http://static.string" title="does not change" text="also does not change"}}
```
In this case, there is no need to emit updating opcodes for the
attributes and content curlies.
This optimization also composes nicely, allowing things like `EmberID`
or `hasBlock` to return const references and take advantage of the same
optimization to drop unnecessary update work.
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A const reference cannot change, so we do not need to emit an updating opcode for them.
For example:
In this case, the conditional is a literal, so it is impossible for the the {{#if}} to flip from default to inverse on the update pass, hence there is no need to emit an
Assertfor the conditional value.While this in itself is pretty rare, it is quite common for this to happen indirectly. For example:
In this case, there is no need to emit updating opcodes for the attributes and content curlies.
This optimization also composes nicely, allowing things like
EmberIDorhasBlockto return const references and drop the unnecessary work.This is also quite noticeable because we don't currently distinguish between "component element" (whose attributes can be "clobbered" by the invocation) and a regular element, so all the "static" attributes still go through the merging policy object. (See 07069c6) With this optimization, we at least do not pay an extra cost for those static attributes on update. (We should come back to optimize non-component elements more.)
Another example: