Bugfix for memset

Author: reeselevine

ggml/src/ggml-webgpu/wgsl-shaders/memset.wgsl

@@ -19,20 +19,20 @@ fn main(@builtin(global_invocation_id) gid: vec3<u32>) {
     let start = params.offset;
     let end = params.offset + params.size;
 
-    for (var j: u32 = 0u; j < bytes_per_thread; j = j + 1u) {
+    for (var j: u32 = 0u; j < bytes_per_thread; j += 4) {
         let byte_index = start + i + j;
-        if (byte_index + 4u <= end) {
-            output_buffer[(byte_index >> 2u)] = params.value;
+        if (byte_index + 4 <= end) {
+            output_buffer[byte_index >> 2] = params.value;
         } else {
             // Handle tail (unaligned)
-            for (var k: u32 = 0u; k < 4u; k = k + 1u) {
+            for (var k: u32 = 0; k < 4; k++) {
                 let idx = byte_index + k;
                 if (idx < end) {
-                    let word_idx = idx >> 2u;
-                    let byte_offset = (idx & 3u) * 8u;
-                    let mask = ~(0xffu << byte_offset);
+                    let word_idx = idx >> 2;
+                    let bit_offset = (idx & 3) * 8u;
+                    let mask = ~(0xffu << bit_offset);
                     let existing = output_buffer[word_idx];
-                    output_buffer[word_idx] = (existing & mask) | ((params.value & 0xffu) << byte_offset);
+                    output_buffer[word_idx] = (existing & mask) | (((params.value >> bit_offset) & 0xff) << bit_offset);
                 }
             }
         }