[perf] wasm is not using resizable array buffer

[loynoir]

Describe the Bug

[perf] wasm is not using resizable array buffer.

Steps to Reproduce

use wasm_bindgen::prelude::wasm_bindgen;

#[wasm_bindgen]
pub fn hello() -> Vec<u8> {
    vec![0u8; 42]
}

Import generated wasm module and inspect wasm memory.

Find wasm is not using resizable array buffer.

> mod.__wasm.memory.buffer.resizable
false
> mod.__wasm.memory.buffer.byteLength 
1114112
> void (ab0 = mod.__wasm.memory.buffer)
undefined

Call small allocation related fn first time.

ArrayBuffer is NOT same object.

> void mod.hello()
undefined
> mod.__wasm.memory.buffer.byteLength 
1179648
> void (ab1 = mod.__wasm.memory.buffer)
undefined
> ab1 === ab0
false

Call small allocation related fn second time.

ArrayBuffer is same object.

> void mod.hello()
undefined
> mod.__wasm.memory.buffer.byteLength 
1179648
> void (ab2 = mod.__wasm.memory.buffer)
undefined
> ab2 === ab1
true

> 1179648 - 1114112
65536

Expected Behavior

When actual allocation, wasm memory buffer is same ArrayBuffer .

Actual Behavior

When actual allocation, wasm memory buffer is NOT same ArrayBuffer .

Not sure it is done by COPY or not.

Additional Context

Not sure ab0 is COPY to ab1 or not.

Should have benchmark comparing with using resizable array buffer as wasm memory buffer.