OpCapability StorageImageRead/WriteWithoutFormat is added to spirv in spirv_1_3 profile when it's not required by the shader

[jjiangweilan]

If I compile the following code with Vulkan 1.1 with profile spirv_1_3. The Vulkan validation layer will throw an error because OpCapability StorageImageReadWithoutFormat and OpCapability StorageImageWriteWithoutFormat are added while it's not necessary

[ VUID-VkShaderModuleCreateInfo-pCode-08740 ] | MessageID = 0x6e224e9 | vkCreateShaderModule():  SPIR-V Capability StorageImageReadWithoutFormat was declared, but one of the following requirements is required (VkPhysicalDeviceFeatures::shaderStorageImageReadWithoutFormat OR VK_VERSION_1_3 OR VK_KHR_format_feature_flags2). The Vulkan spec states: If pCode is a pointer to SPIR-V code, and pCode declares any of the capabilities listed in the SPIR-V Environment appendix, one of the corresponding requirements must be satisfied (https://www.khronos.org/registry/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-VkShaderModuleCreateInfo-pCode-08740)

struct PerMaterial
{
RWTexture2D<float4> outputTex;
}

ParameterBlock<PerMaterial> perMaterial;

[shader("compute")]
[numthreads(8,8,1)]
void FragmentMain(uint3 id : SV_DispatchThreadID)
{
    perMaterial.outputTex[id.xy] = float4(0.5);
}

[csyonghe]

I believe these two capabilities are required because the texture does not specify its storage format. You will need to mark your texture declaration with [format("rgba8")] attribute to remove the requirement.

[fairywreath]

@csyonghe These caps are enabled by this code in slang-emit-spirv.cpp:

// TODO: It may not be necessary to have both of these
// depending on if we read or write
requireSPIRVCapability(SpvCapabilityStorageImageReadWithoutFormat);
requireSPIRVCapability(SpvCapabilityStorageImageWriteWithoutFormat);

when checking texture type, in this case RWTexture2D.

We should be able to do something like moving these from being enabled here to during load/store and subscript set/get calls so we can enable them individually. although this would require some work. In the example above only SpvCapabilityStorageImageWriteWithoutFormat should be enabled.

[jjiangweilan]

I believe these two capabilities are required because the texture does not specify its storage format. You will need to mark your texture declaration with [format("rgba8")] attribute to remove the requirement.

thank you for the reply. It's indeed my lack of understanding.