refactor: move model-specific operators and fusions into backend extensions (#2253)

cmake/cutlass.cmake

@@ -0,0 +1,20 @@
+set(sd_cutlass_default "${PROJECT_SOURCE_DIR}/thirdparty/cutlass")
+if(NOT DEFINED SD_CUDA_CUTLASS_PATH AND DEFINED GGML_CUDA_CUTLASS_PATH)
+    get_filename_component(sd_old_cutlass_default "${SD_GGML_SOURCE_DIR}/src/ggml-cuda/vendors/cutlass" ABSOLUTE)
+    if(NOT GGML_CUDA_CUTLASS_PATH STREQUAL sd_old_cutlass_default)
+        set(sd_cutlass_default "${GGML_CUDA_CUTLASS_PATH}")
+    endif()
+    message(STATUS "Migrating GGML_CUDA_CUTLASS_PATH to SD_CUDA_CUTLASS_PATH")
+endif()
+set(SD_CUDA_CUTLASS_PATH "${sd_cutlass_default}" CACHE PATH "sd: CUTLASS source directory for INT8 GEMM and CuTe attention, empty to disable")
+unset(GGML_CUDA_CUTLASS_PATH CACHE)
+if(SD_CUDA_CUTLASS_PATH)
+    if(NOT EXISTS "${SD_CUDA_CUTLASS_PATH}/include/cutlass/gemm/kernel/default_gemm_universal_with_visitor.h" OR
+       NOT EXISTS "${SD_CUDA_CUTLASS_PATH}/include/cute/tensor.hpp")
+        message(FATAL_ERROR
+            "CUTLASS headers not found at ${SD_CUDA_CUTLASS_PATH}. "
+            "Run git submodule update --init --recursive from the sd.cpp repository root, "
+            "set SD_CUDA_CUTLASS_PATH to a CUTLASS source tree (tested with 3.9.2), "
+            "or set SD_CUDA_CUTLASS_PATH to an empty string to disable CUTLASS.")
+    endif()
+endif()