determine fht_avx.c/fht_neon.c based on CMake target processor (#8346)

Might fix #6691.

Author: swolchok

build/cmake_deps.toml

@@ -386,10 +386,7 @@ buck_targets = [
   "//extension/llm/custom_ops:custom_ops",
 ]
 filters = [
-  # Second clause is to pick up fht_neon.c/fht_avx.c from FFHT. TODO:
-  # remove filters and patch extract_sources.py's Buck query to fetch
-  # srcs; presumably filters is here to remove .h files.
-  "(.cpp$)|(fht.*\\.c$)",
+  ".cpp$",
 ]
 excludes = [
   "^codegen",

extension/llm/custom_ops/CMakeLists.txt

@@ -45,6 +45,22 @@ list(APPEND custom_ops_libs cpuinfo)
 list(APPEND custom_ops_libs cpublas)
 list(APPEND custom_ops_libs eigen_blas)
 
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64|arm64|armv7)$")
+  list(APPEND _custom_ops__srcs
+       "extension/llm/custom_ops/spinquant/third-party/FFHT/fht_neon.c"
+  )
+elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
+  list(APPEND _custom_ops__srcs
+       "extension/llm/custom_ops/spinquant/third-party/FFHT/fht_avx.c"
+  )
+else()
+  message(
+    FATAL_ERROR
+      "Unsupported CMAKE_SYSTEM_PROCESSOR ${CMAKE_SYSTEM_PROCESSOR}. (If \
+32-bit x86, try using fht_avx.c and send a PR if it works!)"
+  )
+endif()
+
 list(TRANSFORM _custom_ops__srcs PREPEND "${EXECUTORCH_ROOT}/")
 
 if(NOT EXECUTORCH_BUILD_XNNPACK)