[compiler] Effects for Return/MaybeThrow terminals #33429
Closed
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
[ghstack-poisoned]
This was referenced Jun 3, 2025
github-actions
bot
added
the
React Core Team
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
This was referenced Jun 6, 2025
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
```js
const x = [];
try {
throwInput(x);
} catch (x_alias) {
mutate(x_alias); // mutates x!
}
```
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions! `c = a.b` can throw, for example, but only with an error generated by the runtime, not with a user value.
Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.
[ghstack-poisoned]
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Stack from ghstack (oldest at bottom):
Adds explicit freeze effects for Return terminals and, more importantly, adds effects for MaybeThrow terminals. MaybeThrow is super interesting. The idea of the terminal is to represent that control-flow can break from nearly any instruction to the error handler (catch). InferMutableRanges has a pass that explicitly handles the corresponding data flow, saying that for any instruction in a block ending in MaybeThrow, to alias the instruction's lvalue to the catch handler. This is to handle cases like this:
One realization is that this logic was overly pessimistic: most instruction types cannot actually throw their lvalue. In fact, the only things that can throw their lvalue are call expressions!
c = a.bcan throw, for example, but only with an error generated by the runtime, not with a user value.Doing this allows us to encode the data flow once and then not have to handle wiring up this data again later.