[webgpu] Use numbers directly instead of const variables in shader'…

…s global scope

FIXES BUG: tensorflow#6746
Deno uses Naga for wgsl compilation, but Naga currently uses let for global constants(will be fixed in gfx-rs/naga#1829).
This PR helps WebGPU to run pose-detection models on Deno by removing global constants in shaders.

Address comments

tfjs-backend-webgpu/src/argminmax_webgpu.ts

@@ -67,6 +67,7 @@ export class ArgMinMaxProgram implements WebGPUProgram {
   }
 
   getUserCode(): string {
+    const workgroupSizeX = this.workgroupSize[0];
     const getInputShapeLastDim = () => {
       if (this.inputShape.length === 1) {
         return 'uniforms.xShape';
@@ -91,8 +92,8 @@ export class ArgMinMaxProgram implements WebGPUProgram {
 
     if (this.type === 'shared') {
       const sharedMemorySnippet = `
-      var<workgroup> xBestIndices : array<i32, ${this.workgroupSize[0]}>;
-      var<workgroup> xBestValues : array<f32, ${this.workgroupSize[0]}>;
+      var<workgroup> xBestIndices : array<i32, ${workgroupSizeX}>;
+      var<workgroup> xBestValues : array<f32, ${workgroupSizeX}>;
     `;
       const userCode = `
       fn DIV_CEIL(a : u32, b : u32) -> u32 {
@@ -102,14 +103,14 @@ export class ArgMinMaxProgram implements WebGPUProgram {
       ${sharedMemorySnippet}
 
       ${main('index')} {
-        let outputIndex = index / i32(workgroupSizeX);
+        let outputIndex = index / ${workgroupSizeX};
         let reduceLength = ${getInputShapeLastDim()};
 
         var bestIndex = i32(localId.x);
         var bestValue = uniforms.infinityValue;
         let outputCoords = getCoordsFromIndex(outputIndex);
         for (var k = i32(localId.x); k < reduceLength && outputIndex < uniforms.size;
-            k = k + i32(workgroupSizeX)) {
+            k = k + ${workgroupSizeX}) {
           let candidate = getX(${splitOutputCoords()} k);
           if (!isnan(candidate) && candidate ${this.op} bestValue) {
             bestValue = candidate;
@@ -120,7 +121,7 @@ export class ArgMinMaxProgram implements WebGPUProgram {
         xBestIndices[localId.x] = bestIndex;
         workgroupBarrier();
 
-        var reduceSize = min(u32(reduceLength), workgroupSizeX);
+        var reduceSize = min(u32(reduceLength), ${workgroupSizeX}u);
         for (var currentSize = reduceSize / 2u; reduceSize > 1u;
             currentSize = reduceSize / 2u) {
           let interval = DIV_CEIL(reduceSize, 2u);

tfjs-backend-webgpu/src/depthwise_conv2d_vec4_webgpu.ts

@@ -69,6 +69,8 @@ export class DepthwiseConv2DVec4Program implements WebGPUProgram {
   getUserCode(): string {
     const xNumber = (this.workPerThread - 1) * this.convInfo.strideWidth +
         this.convInfo.filterWidth;
+    const strideHeight = this.convInfo.strideHeight;
+    const strideWidth = this.convInfo.strideWidth;
 
     const userCode = `
       ${activationFnSnippet(this.activation, this.hasPreluActivation, true, 4)}
@@ -80,14 +82,12 @@ export class DepthwiseConv2DVec4Program implements WebGPUProgram {
         return value;
       }
 
-      const strideHeight = ${this.convInfo.strideHeight};
-      const strideWidth = ${this.convInfo.strideWidth};
       ${main()} {
         let batch = i32(globalId.z) / uniforms.outShape[1];
         let r = i32(globalId.z) % uniforms.outShape[1];
         let c = i32(globalId.y) * ${this.workPerThread};
         let d1 = i32(globalId.x) * 4;
-        let xRCCorner = vec2<i32>(r, c) * vec2<i32>(strideHeight, strideWidth) - uniforms.pad;
+        let xRCCorner = vec2<i32>(r, c) * vec2<i32>(${strideHeight}, ${strideWidth}) - uniforms.pad;
 
         let xRCorner = xRCCorner.x;
         let xCCorner = xRCCorner.y;
@@ -107,7 +107,7 @@ export class DepthwiseConv2DVec4Program implements WebGPUProgram {
             for (var wC = 0; wC < ${this.convInfo.filterWidth}; wC = wC + 1) {
               let wValue = getW(wR, wC, d1, 0);
               for (var i = 0; i < ${this.workPerThread}; i++) {
-                dotProd[i] = fma(xVals[i * strideWidth + wC], wValue, dotProd[i]);
+                dotProd[i] = fma(xVals[i * ${strideWidth} + wC], wValue, dotProd[i]);
               }
             }
           }