From e8711389907caf9f21e5150bfa58660be12b395d Mon Sep 17 00:00:00 2001
From: Yulong Wang <7679871+fs-eire@users.noreply.github.com>
Date: Fri, 27 May 2022 16:12:56 -0700
Subject: [PATCH] slice (scalar)

---
 .../lib/onnxjs/backends/webgpu/ops/slice.ts   | 35 ++++++++++++++++---
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/js/web/lib/onnxjs/backends/webgpu/ops/slice.ts b/js/web/lib/onnxjs/backends/webgpu/ops/slice.ts
index fda8659993188..c5642c0921811 100644
--- a/js/web/lib/onnxjs/backends/webgpu/ops/slice.ts
+++ b/js/web/lib/onnxjs/backends/webgpu/ops/slice.ts
@@ -41,6 +41,29 @@ export const parseSliceAttributes: OperatorInitialization<SliceAttributes> = (no
   return createAttributeWithCacheKey({starts, ends, axes});
 };
 
+const offsetToIndices = (offset: string, strides: readonly number[], indicesPrefix: string): string => {
+  const outputLines: string[] = [];
+
+  for (let i = 0; i < strides.length - 1; i++) {
+    outputLines.push(`var ${indicesPrefix}${i}=${offset}/${strides[i]}u;`);
+    outputLines.push(`${offset}%=${strides[i]}u;`);
+  }
+  outputLines.push(`var ${indicesPrefix}${strides.length - 1}=${offset};`);
+
+  return outputLines.join('\n');
+};
+
+const indicesToOffset = (indicesPrefix: string, strides: readonly number[], offset: string): string => {
+  const outputLines: string[] = [];
+
+  for (let i = 0; i < strides.length - 1; i++) {
+    outputLines.push(`${offset}+=${indicesPrefix}${i} * ${strides[i]}u;`);
+  }
+  outputLines.push(`${offset}+=${indicesPrefix}${strides.length - 1};`);
+
+  return outputLines.join('\n');
+};
+
 const createSliceProgramInfo = (input: Tensor, attributes: SliceAttributes, dataType = 'f32'): ProgramInfo => {
   const axes = (attributes.axes.length === 0) ? input.dims.slice(0).map((val, i) => i) : attributes.axes;
   const normalizedAxes = ShapeUtil.normalizeAxes(axes, input.dims.length);
@@ -59,12 +82,11 @@ const createSliceProgramInfo = (input: Tensor, attributes: SliceAttributes, data
 
   const outputShape = input.dims.slice();
 
-  const sliceOps: Array<[number, number]> = [];
+  const sliceOps: string[] = [];
   for (let i = 0; i < normalizedAxes.length; i++) {
     outputShape[normalizedAxes[i]] = ends[i] - starts[i];
     if (starts[i] > 0) {
-      // sliceOps.push(`outputIdx[${normalizedAxes[i]}] += ${starts[i]};`);
-      sliceOps.push([normalizedAxes[i], starts[i]]);
+      sliceOps.push(`idx_${normalizedAxes[i]} += ${starts[i]}u;`);
     }  // else { sliceOps.push(`outputIdx[${normalizedAxes[i]}] += 0;`); }
   }
 
@@ -84,8 +106,11 @@ const createSliceProgramInfo = (input: Tensor, attributes: SliceAttributes, data
     }
 
     var offset = global_id.x;
-    ${sliceOps.map(i => `offset += ${i[1]}u * ${outputStrides[i[0]]}u;`).join('')}
-    output[global_id.x] = input[offset];
+    ${offsetToIndices('offset', outputStrides, 'idx_')}
+    ${sliceOps.join('')}
+    var offsetInput = 0u;
+    ${indicesToOffset('idx_', ShapeUtil.computeStrides(input.dims), 'offsetInput')}
+    output[global_id.x] = input[offsetInput];
   }`;
   return {
     ...sliceProgramMetadata,