Infer dtype in wasm fill (#7953)

Co-authored-by: Ping Yu <[email protected]>

Author: sklum

tfjs-backend-wasm/src/kernels/Fill.ts

@@ -15,13 +15,17 @@
  * =============================================================================
  */
 
-import {KernelConfig, KernelFunc} from '@tensorflow/tfjs-core';
+import {KernelConfig, KernelFunc, util} from '@tensorflow/tfjs-core';
 import {Fill, FillAttrs} from '@tensorflow/tfjs-core';
 
 import {BackendWasm} from '../backend_wasm';
 
 export function fill(args: {attrs: FillAttrs, backend: BackendWasm}) {
-  const {attrs: {shape, value, dtype}, backend} = args;
+  const {attrs: {shape, value}, backend} = args;
+  let {attrs: {dtype}} = args;
+
+  dtype = dtype || util.inferDtype(value);
+
   const out = backend.makeOutput(shape, dtype);
   const outVals = backend.typedArrayFromHeap(out);
   outVals.fill(value as number);