Restored comment lost in merge.

Improved mip count function to avoid need for some platform specific code.

ScriptableRenderPipeline/Core/CoreRP/ShaderLibrary/Common.hlsl

 // The reason is that for compute shader we need to guarantee that the layout of CBs is consistent across kernels. Something that we can't control with the global namespace (uniforms get optimized out if not used, modifying the global CBuffer layout per kernel)
 
 // Structure definition that are share between C# and hlsl.
-// These structures need to be align on float4 to respect various packing rules from shader language.
-// This mean that these structure need to be padded.
+// These structures need to be align on float4 to respect various packing rules from shader language. This mean that these structure need to be padded.
+// Rules: When doing an array for constant buffer variables, we always use float4 to avoid any packing issue, particularly between compute shader and pixel shaders
+// i.e don't use SetGlobalFloatArray or SetComputeFloatParams
+// The array can be alias in hlsl. Exemple:
+// uniform float4 packedArray[3];
+// static float unpackedArray[12] = (float[12])packedArray;
 
 // The function of the shader library are stateless, no uniform decalare in it.
 // Any function that require an explicit precision, use float or half qualifier, when the function can support both, it use real (see below)
 
 uint GetMipCount(Texture2D tex)
 {
-#if defined(SHADER_API_D3D11) || defined(SHADER_API_D3D12) || defined(SHADER_API_D3D11_9X) || defined(SHADER_API_XBOXONE) || defined(SHADER_API_PSSL)
+#if defined(SHADER_API_D3D11) || defined(SHADER_API_D3D12) || defined(SHADER_API_D3D11_9X) || defined(SHADER_API_XBOXONE) || defined(SHADER_API_PSSL)
+    #define MIP_COUNT_SUPPORTED 1
+#endif
+#if (defined(SHADER_API_OPENGL) || defined(SHADER_API_VULKAN)) && !defined(SHADER_STAGE_COMPUTE)
+    // OpenGL only supports textureSize for width, height, depth
+    // textureQueryLevels (GL_ARB_texture_query_levels) needs OpenGL 4.3 or above and doesn't compile in compute shaders
+    // tex.GetDimensions converted to textureQueryLevels
+    #define MIP_COUNT_SUPPORTED 1
+#endif
+    // Metal doesn't support high enough OpenGL version
+
+#if defined(MIP_COUNT_SUPPORTED)
-#elif defined(SHADER_API_OPENGL) || defined(SHADER_API_VULKAN)
-    // OpenGL only supports textureSize for width, height, depth
-    // textureQueryLevels (GL_ARB_texture_query_levels) needs OpenGL 4.3 or above and doesn't compile in compute shaders
-    #if SHADER_STAGE_COMPUTE
-    return 0;
-    #else
-    return textureQueryLevels(tex);
-    #endif
 #else
     return 0;
 #endif