WGPU: Add new test and explanation for disabled test (#5731)

* Add buffer swizzle store test using structured buffers

This helps to address #5612

* WGPU: Add explanation for tests/bugs/buffer-swizzle-store.slang

This closes #5612.

* Manual formatting fix

* format code

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

Author: aleino-nv

tests/bugs/buffer-swizzle-store.slang

@@ -1,7 +1,7 @@
 //TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
 //TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
 //TEST(compute):COMPARE_COMPUTE:-slang -shaderobj -mtl -output-using-type
-// Slang-RHI/WGPU: Invalid bind group layout entry used #5612
+// Not supported in WGSL: read-write storage texture with "rg16f" format
 //DISABLE_TEST(compute):COMPARE_COMPUTE_EX:-wgpu
 
 //TEST_INPUT: RWTexture2D(format=R16G16_FLOAT, size=4, content = one, mipMaps = 1):name g_test

tests/compute/structured-buffer-swizzle-store.slang

@@ -0,0 +1,27 @@
+//TEST(compute):COMPARE_COMPUTE: -shaderobj
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4),name=buf
+RWStructuredBuffer<float4> buf;
+
+//TEST_INPUT:ubuffer(data=[0], stride=4):out,name outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    float sum = 0.0f;
+    
+    buf[0].wxyz = float4(1.0, 0.0, 0.0, 0.0);
+    sum += buf[0].w;
+    
+    buf[0].xwyz = float4(0.0, 1.0, 0.0, 0.0);
+    sum += buf[0].w;
+
+    buf[0].xywz = float4(0.0, 0.0, 1.0, 0.0);
+    sum += buf[0].w;
+
+    buf[0].xyzw = float4(0.0, 0.0, 0.0, 1.0);
+    sum += buf[0].w;
+
+    outputBuffer[0] = int(sum);
+}

tests/compute/structured-buffer-swizzle-store.slang.expected.txt

@@ -0,0 +1 @@
+4