Extends VK_QCOM_image_processing with four additional block matching SPIR-V instructions: windowed SAD and SSD (OpImageBlockMatchWindowSADQCOM/OpImageBlockMatchWindowSSDQCOM) that search across a 2D window of block match positions and return the minimum or maximum error metric along with its location, and gather SAD and SSD (OpImageBlockMatchGatherSADQCOM/OpImageBlockMatchGatherSSDQCOM) that compute error metrics at four adjacent horizontal texel offsets simultaneously and return all four results in a single vec4.

The task list for the VK_QCOM_image_processing2 release is:

• Vulkan Specification: https://docs.vulkan.org/refpages/latest/refpages/source/VK_QCOM_image_processing2.html
• SPIRV specification: https://github.khronos.org/SPIRV-Registry/extensions/QCOM/SPV_QCOM_image_processing2.html
• SPIRV Headers: SPV_QCOM_image_processing2 SPIRV-Headers#419
• SPIRV tools released: Add the extension check that SPV_QCOM_image_processing and SPV_QCOM_image_processing2 requires SPV 1.4 or later. SPIRV-Tools#6268
• GLSL extension: https://github.com/KhronosGroup/GLSL/blob/main/extensions/qcom/GLSL_QCOM_image_processing2.txt
• Glslang implementation: A couple of fixes to the GL_QCOM_image_processing2 support glslang#3578
• Validation layer:

As each component is made public, the task will be checked off. When all tasks have been completed this issue will be closed and the extension will be fully released.