[wasm] fix #5021: wechat webassembly support

[deepkolos]

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test demo in repo tfjs-wxmp-wasm-test

related issue: #5021

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[deepkolos]

@googlebot I signed it!

[pyu10055]

Thank you for the contribution, a couple of comments.

Reviewable status: 0 of 1 approvals obtained (waiting on @deepkolos)

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tfjs-backend-wasm/scripts/patch-wechat-webassembly.js, line 16 at r1 (raw file):

        file.endsWith('tfjs-backend-wasm-threaded-simd.js')
      ) {
        code = code.replace(`require("worker_threads")`, 'null')

we prefer to have ';' at the end of the statement.

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tfjs-backend-wasm/scripts/patch-wechat-webassembly.js, line 22 at r1 (raw file):

      // it is not a nice way, but WebAssembly.validate not working and SIMD is not support in WXWebAssembly
      if (file.endsWith('backend_wasm.ts')) {
        code = code.replace(`env().getAsync('WASM_HAS_SIMD_SUPPORT')`, 'false')

this can be done in the wechat plugin, where we can do tf.env().set('WASM_HAS_SIMD_SUPPORT', false), similar with WASM_HAS_MULTITHREAD_SUPPORT

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tfjs-backend-wasm/scripts/patch-wechat-webassembly.js, line 25 at r1 (raw file):

        code = code.replace(`env().getAsync('WASM_HAS_MULTITHREAD_SUPPORT')`, 'false')
        code = code.replace(
          `function createInstantiateWasmFunc(path) {`,

This is bit of hacky to relies on treeshaking to remove the rest of the method, can you use regex to match the whole method?

[deepkolos]

@pyu10055 a better way to replace createInstantiateWasmFunc

[deepkolos]

and test case updated

tf.env().set('WASM_HAS_SIMD_SUPPORT', false);
tf.env().set('WASM_HAS_MULTITHREAD_SUPPORT', false);

https://github.com/deepkolos/tfjs-wxmp-wasm-test/blob/ebe95a1a036c1a29ab8a7a980d5f2d2099a1ea99/pages/index/index.js#L15

[pyu10055]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @deepkolos)

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tfjs-backend-wasm/scripts/patch-wechat-webassembly.js, line 35 at r2 (raw file):

Previously, deepkolos (DeepKolos) wrote…

and test case updated

tf.env().set('WASM_HAS_SIMD_SUPPORT', false);
tf.env().set('WASM_HAS_MULTITHREAD_SUPPORT', false);

https://github.com/deepkolos/tfjs-wxmp-wasm-test/blob/ebe95a1a036c1a29ab8a7a980d5f2d2099a1ea99/pages/index/index.js#L15

This is very nice, thanks you!

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tfjs-backend-wasm/src/backend_wasm.ts, line 213 at r3 (raw file):

function createInstantiateWasmFunc(path: string) {
  // this will be replace by rollup plugin patchWechatWebAssembly in minprogram's output

is this comment still needed, or should it be updated to reflect your new solution?