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[threads][js-api] Preserve SharedArrayBuffer identity on grow(0) #255

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[threads][js-api] Preserve SharedArrayBuffer identity on grow(0) #255

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18 changes: 15 additions & 3 deletions document/js-api/index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -710,6 +710,9 @@ To create a resizable memory buffer we perform the same steps as above, but also
1. Assert: |map|[|memaddr|] [=map/exists=].
1. Let |memory| be |map|[|memaddr|].
1. Let |buffer| be |memory|.\[[BufferObject]].
1. If [$IsSharedArrayBuffer$](|buffer|) is true,
1. Let |block| be a [=Shared Data Block=] which is [=identified with=] the underlying memory of |memaddr|.
1. If |buffer|.\[[ArrayBufferByteLength]] is equal to the length of |block|, return.
1. If [$IsFixedLengthArrayBuffer$](|buffer|) is true,
1. If [$IsSharedArrayBuffer$](|buffer|) is false,
1. Perform [=!=] [$DetachArrayBuffer$](|buffer|, "WebAssembly.Memory").
Expand All @@ -730,8 +733,11 @@ To create a resizable memory buffer we perform the same steps as above, but also
1. Let |store| be [=mem_grow=](|store|, |memaddr|, |delta|).
1. If |store| is [=error=], throw a {{RangeError}} exception.
1. Set the [=surrounding agent=]'s [=associated store=] to |store|.
1. [=Refresh the memory buffer=] of |memaddr|.
1. Let <var ignore>limits</var> |share| be [=mem_type=](|store|, |memaddr|).
1. If |share| is unshared, [=refresh the Memory buffer=] of |memaddr|.
1. Return |ret|.

Note: For shared memories, the refresh is deferred until the next access to the {{buffer}} property. This is a non-observable performance optimization.
</div>

<div algorithm=dom-Memory-grow>
Expand All @@ -747,7 +753,11 @@ Immediately after a WebAssembly [=memory.grow=] instruction executes, perform th
1. Let |frame| be the [=current frame=].
1. Assert: due to validation, |frame|.[=frame/module=].[=moduleinst/memaddrs=][0] exists.
1. Let |memaddr| be the memory address |frame|.[=frame/module=].[=moduleinst/memaddrs=][0].
1. [=Refresh the memory buffer=] of |memaddr|.
1. Let |store| be the [=surrounding agent=]'s [=associated store=].
1. Let <var ignore>limits</var> |share| be [=mem_type=](|store|, |memaddr|).
1. If |share| is unshared, [=refresh the Memory buffer=] of |memaddr|.

Note: For shared memories, the refresh is deferred until the next access to the {{buffer}} property. This is a non-observable performance optimization.
</div>

<div algorithm=dom-Memory-toFixedLengthBuffer>
Expand All @@ -762,6 +772,7 @@ Immediately after a WebAssembly [=memory.grow=] instruction executes, perform th
1. Set **this**.\[[BufferObject]] to |fixedBuffer|.
1. Return |fixedBuffer|.
1. Otherwise,
1. [=Refresh the Memory buffer=] of |memaddr|.
1. Let |map| be the [=surrounding agent=]'s associated [=Memory object cache=].
1. Assert: |map|[|memaddr|] [=map/exists=].
1. Let |newMemory| be |map|[|memaddr|].
Expand Down Expand Up @@ -827,11 +838,12 @@ Immediately after a WebAssembly [=memory.grow=] instruction executes, perform th
Note: (TODO) Check the error case of memory.grow on the Wasm side.

<div algorithm>
The getter of the <dfn attribute for="Memory">buffer</dfn> attribute of {{Memory}} perfoms the following steps:
The getter of the <dfn attribute for="Memory">buffer</dfn> attribute of {{Memory}} performs the following steps:

1. Let |memaddr| be **this**.\[[Memory]].
1. Let |block| be a [=Data Block=] which is [=identified with=] the underlying memory of |memaddr|.
1. If |block| is a [=Shared Data Block=],
1. [=Refresh the Memory buffer=] of |memaddr|.
1. Let |map| be the [=surrounding agent=]'s associated [=Memory object cache=].
1. Assert: |map|[|memaddr|] [=map/exists=].
1. Let |newMemory| be |map|[|memaddr|].
Expand Down
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