Add memory64 and table64 support to the Canonical ABI by adambratschikaye · Pull Request #624 · WebAssembly/component-model

adambratschikaye · 2026-03-17T14:47:08Z

Parameterize the Canonical ABI to handle 32-bit or 64-bit memory addresses and table indices. This is done by adding two new fields to LiftOptions to indicate if the memory64/table64 feature is being used in a core module.

Parameterize the Canonical ABI to handle 32-bit or 64-bit memory addresses and table indices. This is done by adding two new fields to `LiftOptions` to indicate if the `memory64`/`table64` feature is being used in a core module.

alexcrichton

Thanks so much for helping to pick this up! We chatted a bit on Zulip but for posterity I'll mention here about table-related index types how most of them want to remain 32-bits. I'll take a closer look once that's been passed over here, and in the meantime I skimmed over things and noted a few things here and there. I'm sure though that @lukewagner will have thoughts on this too!

alexcrichton · 2026-03-17T16:06:12Z

design/mvp/Explainer.md

-      (param $originalSize i32)
+(func (param $originalPtr $addr)
+      (param $originalSize $addr)
      (param $alignment i32)


For this I might recommend making alignment have type $addr as well for consistency, and I think that matches the signature in Rust/C/etc as well.

alexcrichton · 2026-03-17T16:07:46Z

design/mvp/Explainer.md

 | -------------------------- | ------------------------ |
 | Approximate WIT signature  | `func<T>(t: T) -> T.rep` |
-| Canonical ABI signature    | `[t:i32] -> [i32]`       |
+| Canonical ABI signature    | `[t:$idx] -> [i32]`      |


This'll be a bit subtle, but this'll actually want to be a mapping of i32 as an argument (I talked with you a bit about this already, but the input here is a host-side index so always 32-bit), but the output here should be something variable. Resource "rep"s are generally pointers in linear memory so 64-bit components are going to want 64-bit storage values. In the component model resources are defined with (rep i32) and validation currently requires that i32 is the only one listed there, but this PR will relax that meaning that the resource type itself stores the lowered type which'll get plumbed here.

Thanks, I've now changed it so that the types which are expected to be pointers to memory are allowed to be either i32 or i64 without forcing them to match the memory type (e.g. the return value here, or in context.{get,set}, or thread.new-indirect). This means we don't need to require the memory canonopt anywhere where it didn't previously exist.

alexcrichton

Looks good to me! I think this'll need minor adjustments over time but overall looks good 👍

alexcrichton · 2026-03-20T06:31:12Z

design/mvp/canonical-abi/definitions.py

+  if opts.memory is None:
+    return 'i32'


Could this have an assert? This in theory shouldn't ever be called dynamically if memory is None

alexcrichton · 2026-03-20T06:34:21Z

design/mvp/CanonicalABI.md

+* `memory` - this is a subtype of `(memory 1)`. In the rest of the explainer,
+  `PTR` will refer to either `i32` or `i64` core Wasm types as determined by the
+  type of this `memory`.


This'll technically want to say it's a subtype of memory 1 or memory i64 1 since those are separate types

alexcrichton · 2026-03-20T06:34:55Z

design/mvp/CanonicalABI.md

  feature (the "stackful" ABI), this restriction is lifted.
-* 🔀 `callback` - the function has type `(func (param i32 i32 i32) (result i32))`
-  and cannot be present without `async` and is only allowed with
+* 🔀 `callback` - the function has type `(func (param i32 i32 PTR) (result i32))`


I think this one may remain a three i32s since they're all async-related codes/events/etc.

lukewagner

This looks great overall; thanks so much for all the work and adding tests too! There's only one relatively minor, but non-nit, suggestion below that I'm happy to discuss and then re-review based on what we decide.

design/mvp/canonical-abi/definitions.py

design/mvp/canonical-abi/run_tests.py

design/mvp/Concurrency.md

design/mvp/CanonicalABI.md

design/mvp/canonical-abi/definitions.py

Co-authored-by: Luke Wagner <mail@lukewagner.name>

design/mvp/Explainer.md

adambratschikaye · 2026-04-07T15:17:11Z

Other than that, this looks great to implement. One question is whether we think we'll get implementation feedback soon enough to want to keep the PR open until so we can simply iterate on it here, or whether we think it'd be more valuable to merge it now, and iterate in separate PRs if/when tweaks are found. Happy to hear what you and @alexcrichton think we should do.

We should start work in the next week on implementation.

lukewagner

Looks good to me, thanks! Now that things are gated, I'll merge once these nits are fixed.

design/mvp/CanonicalABI.md

Co-authored-by: Luke Wagner <mail@lukewagner.name>

adambratschikaye · 2026-04-09T07:06:59Z

Thanks again @lukewagner !

lukewagner · 2026-04-09T16:19:02Z

And thank you again for working on this!

Add memory64 and table64 support to the Canonical ABI

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Parameterize the Canonical ABI to handle 32-bit or 64-bit memory addresses and table indices. This is done by adding two new fields to `LiftOptions` to indicate if the `memory64`/`table64` feature is being used in a core module.

alexcrichton reviewed Mar 17, 2026

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adambratschikaye added 4 commits March 18, 2026 15:14

Correct types that are in host tables.

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Use existing canonical options and static parameters

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typo

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small fixes

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alexcrichton reviewed Mar 20, 2026

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review comments

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lukewagner requested changes Mar 23, 2026

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adambratschikaye and others added 15 commits March 24, 2026 10:47

some test cleanup

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fix spacing

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Co-authored-by: Luke Wagner <mail@lukewagner.name>

fix spacing

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fix spacing

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inline table.addrtype

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inline table.addrtype

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fixup inline table.addrtype

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add MemInst class

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inline memory defaults in tests

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revert max string length to a const

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replace PTR with memory.addrtype

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note on buffer size

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clarify address type

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mixed context types behavior

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fix 32 bit mask

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adambratschikaye force-pushed the abk/memory64 branch from 0b5e62d to 4fd7d8b Compare March 25, 2026 13:27

adambratschikaye added 4 commits March 25, 2026 14:05

transparent indexing on MemInst

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undo old change

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revert some small changes

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check list and string lengths when loading

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adambratschikaye marked this pull request as ready for review March 26, 2026 15:39

adambratschikaye added 5 commits April 7, 2026 06:51

review comments

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Merge remote-tracking branch 'origin/abk/memory64' into abk/memory64

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bound string length by bytes

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elephant emoji gate and i64 resource production

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update resource types with emoji

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adambratschikaye commented Apr 7, 2026

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adambratschikaye requested a review from lukewagner April 7, 2026 15:17

lukewagner approved these changes Apr 8, 2026

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adambratschikaye and others added 18 commits April 9, 2026 08:27

Update design/mvp/CanonicalABI.md

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Co-authored-by: Luke Wagner <mail@lukewagner.name>

Update design/mvp/CanonicalABI.md

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merge load length limits into REALLOC_I32_MAX

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Merge branch 'main' into abk/memory64

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lukewagner merged commit a6dfd37 into WebAssembly:main Apr 9, 2026
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