pulley: Implement interpreter-to-host calls #9665
Open
Conversation
This file contains 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
alexcrichton
requested review from
abrown and
pchickey
and removed request for
a team
This commit is an initial stab at implementing interpreter-to-host communication in Pulley. The basic problem is that Pulley needs the ability to call back into Wasmtime to implement tasks such as `memory.grow`, imported functions, etc. For native platforms this is a simple `call_indirect` operation in Cranelift but the story for Pulley must be different because it's effectively switching from interpreted code to native code. The initial idea for this in bytecodealliance#9651 is replaced here and looks mostly similar but with a few changes. The overall structure of how this works is: * A new `call_indirect_host` opcode is added to Pulley. * Function signatures that can be called from Pulley bytecode are statically enumerated at build-time. * This enables the implementation of `call_indirect_host` to take an immediate of which signature is being used and cast the function pointer to the right type. * A new pulley-specific relocation is added to Cranelift for this opcode. * `RelocDistance::Far` calls to a name trigger the use of `call_indirect_host`. * The relocation is filled in by Wasmtime after compilation where the signature number is inserted. * A new `NS_*` value for user-function namespaces is reserved in `wasmtime-cranelift` for this new namespace of functions. * Code generation for Pulley in `wasmtime-cranelift` now has Pulley-specific handling of the wasm-to-host transition where all previous `call_indirect` instructions are replaced with a call to a "backend intrinsic" which gets lowered to a `call_indirect_host`. Note that most of this still isn't hooked up everywhere in Wasmtime. That means that the testing here is pretty light at this time. It'll require a fair bit more work to get everything fully integrated from Wasmtime in Pulley. This is expected to be one of the significant remaining chunks of work and should help unblock future testing (or make those diffs smaller ideally).
alexcrichton
force-pushed
the
pulley-host-calls
branch
from
0ea4d86
to
1c9e235
Compare
github-actions
bot
added
cranelift
Subscribe to Label Actioncc @fitzgen
This issue or pull request has been labeled: "cranelift", "cranelift:area:machinst", "pulley", "wasmtime:api"
Thus the following users have been cc'd because of the following labels:
To subscribe or unsubscribe from this label, edit the |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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.
This commit is an initial stab at implementing interpreter-to-host communication in Pulley. The basic problem is that Pulley needs the ability to call back into Wasmtime to implement tasks such as
memory.grow, imported functions, etc. For native platforms this is a simplecall_indirectoperation in Cranelift but the story for Pulley must be different because it's effectively switching from interpreted code to native code.The initial idea for this in #9651 is replaced here and looks mostly similar but with a few changes. The overall structure of how this works is:
call_indirect_hostopcode is added to Pulley.call_indirect_hostto take an immediate of which signature is being used and cast the function pointer to the right type.RelocDistance::Farcalls to a name trigger the use ofcall_indirect_host.NS_*value for user-function namespaces is reserved inwasmtime-craneliftfor this new namespace of functions.wasmtime-craneliftnow has Pulley-specific handling of the wasm-to-host transition where all previouscall_indirectinstructions are replaced with a call to a "backend intrinsic" which gets lowered to acall_indirect_host.Note that most of this still isn't hooked up everywhere in Wasmtime. That means that the testing here is pretty light at this time. It'll require a fair bit more work to get everything fully integrated from Wasmtime in Pulley. This is expected to be one of the significant remaining chunks of work and should help unblock future testing (or make those diffs smaller ideally).