Fix an error caused by glsl mod() function

lib/backends/webgl/ops/im2col-pack.ts

@@ -48,12 +48,11 @@ export class WebGLIm2ColPacked implements WebGLOperator {
 
           if(blockIndex < ${im2colShape[1]} && pos < ${im2colShape[0]}) {
             offsetY = int(blockIndex / (${this.convOutputShape[rank - 1]})) * ${this.strides[0]} - ${this.pads[1]};
-            d0 = offsetY + ${this.dilations[0]} * (int(mod(float(pos), ${kernelSize}.)) / ${wshape[2]} );
+            d0 = offsetY + ${this.dilations[0]} * (imod(pos, ${kernelSize}) / ${wshape[2]});
 
             if(d0 < ${xshape[rowDim]} && d0 >= 0) {
-              offsetX = int(mod(float(blockIndex), ${this.convOutputShape[rank - 1]}.) * ${this.strides[1]}. - ${
-            this.pads[0]}.);
-              d1 = offsetX + ${this.dilations[1]} * (int(mod(mod(float(pos), ${kernelSize}.), ${wshape[2]}.)));
+              offsetX = imod(blockIndex, ${this.convOutputShape[rank - 1]}) * ${this.strides[1]} - ${this.pads[0]};
+              d1 = offsetX + ${this.dilations[1]} * imod(imod(pos, ${kernelSize}), ${wshape[2]});
 
               if(d1 < ${xshape[colDim]} && d1 >= 0) {
 

test/unittests/backends/webgl/test_reshape_packed.ts

@@ -156,5 +156,10 @@ function getTestData(): TestData[] {
       inputShape: [2, 2, 2, 4],
       outputShape: [2, 1, 4, 4],
     },
+    {
+      elementCount: 18432,
+      inputShape: [512, 36, 1, 1],
+      outputShape: [512, 36],
+    },
   ];
 }