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Document coroutines codegen: suspend markers: JS & Native

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Ilmir Usmanov
2020-08-14 01:04:36 +02:00
committed by Ilmir Usmanov
parent f7cf5f435f
commit 307e01e6b6
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compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/coroutines-codegen.md
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@@ -274,4 +274,15 @@ to `kotlin.jvm.internal.InlineMarker.mark`'s call cannot be changed.
The codegen generates the markers by calling `addSuspendMarker`. After generating `MethodNode` of the function, it passes the node to The codegen generates the markers by calling `addSuspendMarker`. After generating `MethodNode` of the function, it passes the node to
`CoroutineTransformerMethodVisitor`. `CoroutineTransformerMethodVisitor` collects the suspension `CoroutineTransformerMethodVisitor`. `CoroutineTransformerMethodVisitor` collects the suspension
points by checking these markers, and then it generates the state-machine. points by checking these markers, and then it generates the state-machine.
FIXME: I should rename `CoroutineTransformerMethodVisitor` to `StateMachineBuilder` already. FIXME: I should rename `CoroutineTransformerMethodVisitor` to `StateMachineBuilder` already.
#### JS & Native: Suspend Markers
The difference between JVM_IR and JS_IR/Native in regards to coroutine codegen non-JVM back-ends do not generate suspending markers in the
resulting code. They still collect suspension points, however.
That is because they assume the closed-world model; in other words, they do not generate libraries in their target languages, which could
contain suspending inline functions. Thus, the back-ends run the inliner before all lowerings, and they generate state machine during a
suspend lowering, whereas JVM_IR still relies on the old back-end's `CoroutineTransfromerMethodVisitor` to do this since we cannot just
generate state machine during a lowering, there are suspend inline functions in libraries bytecode, because of the open-world model.
Well, we can, if the function does not inline other functions. Nevertheless, there is much work to do in the new back-end, and generating a
state-machine during the lowering is a part of it.