Typed continuations: cont.new instructions#6308
Conversation
tlively
left a comment
tlively
left a comment
There was a problem hiding this comment.
Looks great! Just a few small comments.
src/ir/cost.h
Outdated
|
|
||
| CostType visitContNew(ContNew* curr) { | ||
| // Some arbitrary "high" value, reflecting that this may allocate a stack | ||
| return 10 + visit(curr->func); |
There was a problem hiding this comment.
Would you expect that this would be cheaper than resume, which we model with a base cost of 12?
There was a problem hiding this comment.
Ha, good point! If the stack allocation does happen at cont.new, this should indeed be more expensive than resume. But I could also imagine an implementation strategy where the allocation happens lazily when resume-ing a new continuation for the first time.
In general, I have little confidence in the numbers here. For now, I've increased the base cost for cont.new to 14, which is still very arbitrary, but at least greater than the value for resume. Should I add a TODO that we should probably revisit these values at some point? (e.g., once we have more experience from implementing the extension)
There was a problem hiding this comment.
Ehh, probably no need for a TODO. All of the numbers in this file are similarly suspect.
src/wasm/wasm-ir-builder.cpp
Outdated
| Result<> IRBuilder::visitContNew(ContNew* curr) { | ||
| auto func = pop(); | ||
| CHECK_ERR(func); | ||
| curr->func = *func; | ||
|
|
||
| return Ok{}; | ||
| } |
There was a problem hiding this comment.
The default visitExpression implementation will already do exactly this, so I don't think we need to implement visitConstNew here at all. If what we popped depended on the contType at all, that would be different.
Co-authored-by: Thomas Lively <tlively123@gmail.com>
This PR is part of a series that adds basic support for the [typed continuations/wasmfx proposal](https://github.com/wasmfx/specfx). This particular PR adds support for the `cont.new` instruction for creating continuations, documented [here(https://github.com/wasmfx/specfx/blob/main/proposals/continuations/Overview.md#instructions). In short, these instructions are of the form `(cont.new $ct)` where `$ct` must be a continuation type. The instruction takes a single (nullable) function reference as its argument, which means that the folded representation of the instruction is of the form `(cont.new $ct (foo ...))`. Support for the instruction is implemented in both the old and the new wat parser. Note that this PR does not implement validation of the new instruction.
This PR is part of a series that adds basic support for the [typed continuations/wasmfx proposal](https://github.com/wasmfx/specfx). This particular PR adds support for the `cont.new` instruction for creating continuations, documented [here(https://github.com/wasmfx/specfx/blob/main/proposals/continuations/Overview.md#instructions). In short, these instructions are of the form `(cont.new $ct)` where `$ct` must be a continuation type. The instruction takes a single (nullable) function reference as its argument, which means that the folded representation of the instruction is of the form `(cont.new $ct (foo ...))`. Support for the instruction is implemented in both the old and the new wat parser. Note that this PR does not implement validation of the new instruction.
2 participants
This PR is part of a series that adds basic support for the typed continuations/wasmfx proposal.
This particular PR adds support for the
cont.newinstruction for creating continuations, documented here.In short, these instructions are of the form
(cont.new $ct)where$ctmust be a continuation type. The instruction takes a single (nullable) function reference as its argument, which means that the folded representation of the instruction is of the form(cont.new $ct (foo ...)).Support for the instruction is implemented in both the old and the new wat parser.
Note that this PR does not implement validation of the new instruction.