[cpu] Dispatch un-quantized linear to oneDNN/ACL by default for AArch64 (#27183)

Signed-off-by: Fadi Arafeh <fadi.arafeh@arm.com>
Co-authored-by: Michael Yang <Michael.Yang@arm.com>

cmake/cpu_extension.cmake

@@ -188,16 +188,47 @@ else()
     message(FATAL_ERROR "vLLM CPU backend requires AVX512, AVX2, Power9+ ISA, S390X ISA, ARMv8 or RISC-V support.")
 endif()
 
-#
-# Build oneDNN for W8A8 GEMM kernels (only for x86-AVX512 /ARM platforms)
-# Flag to enable ACL kernels for AARCH64 platforms
-if (VLLM_BUILD_ACL STREQUAL "ON")
-    set(USE_ACL ON)
-else()
-    set(USE_ACL OFF)
-endif()
 
+# Build oneDNN for GEMM kernels (only for x86-AVX512 /ARM platforms)
 if ((AVX512_FOUND AND NOT AVX512_DISABLED) OR (ASIMD_FOUND AND NOT APPLE_SILICON_FOUND) OR POWER9_FOUND OR POWER10_FOUND OR POWER11_FOUND)
+    # Fetch and build Arm Compute Library (ACL) as oneDNN's backend for AArch64
+    # TODO [fadara01]: remove this once ACL can be fetched and built automatically as a dependency of oneDNN
+    if(ASIMD_FOUND)
+        if(DEFINED ENV{ACL_ROOT_DIR} AND IS_DIRECTORY "$ENV{ACL_ROOT_DIR}")
+            message(STATUS "Using ACL from specified source directory: $ENV{ACL_ROOT_DIR}")
+        else()
+            message(STATUS "Downloading Arm Compute Library (ACL) from GitHub")
+            FetchContent_Populate(arm_compute
+                SUBBUILD_DIR "${FETCHCONTENT_BASE_DIR}/arm_compute-subbuild"
+                SOURCE_DIR   "${FETCHCONTENT_BASE_DIR}/arm_compute-src"
+                GIT_REPOSITORY https://github.com/ARM-software/ComputeLibrary.git
+                GIT_TAG        v52.2.0
+                GIT_SHALLOW    TRUE
+                GIT_PROGRESS   TRUE
+            )
+            set(ENV{ACL_ROOT_DIR} "${arm_compute_SOURCE_DIR}")
+        endif()
+
+        # Build ACL with scons
+        include(ProcessorCount)
+        ProcessorCount(_NPROC)
+        execute_process(
+            COMMAND scons -j${_NPROC}
+                    Werror=0 debug=0 neon=1 examples=0 embed_kernels=0 os=linux
+                    arch=armv8.2-a build=native benchmark_examples=0 fixed_format_kernels=1
+                    multi_isa=1 openmp=1 cppthreads=0
+            WORKING_DIRECTORY "$ENV{ACL_ROOT_DIR}"
+            RESULT_VARIABLE _acl_rc
+        )
+        if(NOT _acl_rc EQUAL 0)
+            message(FATAL_ERROR "ACL SCons build failed (exit ${_acl_rc}).")
+        endif()
+
+        set(ONEDNN_AARCH64_USE_ACL "ON")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,-rpath,$ENV{ACL_ROOT_DIR}/build/")
+        add_compile_definitions(VLLM_USE_ACL)
+    endif()
+
     set(FETCHCONTENT_SOURCE_DIR_ONEDNN "$ENV{FETCHCONTENT_SOURCE_DIR_ONEDNN}" CACHE PATH "Path to a local oneDNN source directory.")
 
     if(FETCHCONTENT_SOURCE_DIR_ONEDNN)
@@ -217,16 +248,6 @@ if ((AVX512_FOUND AND NOT AVX512_DISABLED) OR (ASIMD_FOUND AND NOT APPLE_SILICON
         )
     endif()
 
-    if(USE_ACL)
-        find_library(ARM_COMPUTE_LIBRARY NAMES arm_compute PATHS $ENV{ACL_ROOT_DIR}/build/)
-        if(NOT ARM_COMPUTE_LIBRARY)
-            message(FATAL_ERROR "Could not find ARM Compute Library: please set ACL_ROOT_DIR")
-        endif()
-        set(ONEDNN_AARCH64_USE_ACL "ON")
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,-rpath,$ENV{ACL_ROOT_DIR}/build/")
-        add_compile_definitions(VLLM_USE_ACL)
-    endif()
-
     set(ONEDNN_LIBRARY_TYPE "STATIC")
     set(ONEDNN_BUILD_DOC "OFF")
     set(ONEDNN_BUILD_EXAMPLES "OFF")

requirements/cpu-build.txt

@@ -6,6 +6,7 @@ setuptools-scm>=8
 --extra-index-url https://download.pytorch.org/whl/cpu
 torch==2.8.0+cpu; platform_machine == "x86_64"
 torch==2.8.0; platform_machine == "ppc64le" or platform_machine == "aarch64" or platform_system == "Darwin"
+scons; platform_machine == "aarch64"    # needed to build Arm Compute Library (ACL)
 wheel
 jinja2>=3.1.6
 regex

vllm/model_executor/layers/utils.py

@@ -8,7 +8,7 @@ import torch
 
 from vllm import _custom_ops as ops
 from vllm import envs
-from vllm.platforms import CpuArchEnum, current_platform
+from vllm.platforms import current_platform
 from vllm.utils.torch_utils import direct_register_custom_op
 
 
@@ -178,10 +178,7 @@ def dispatch_cpu_unquantized_gemm(
         )
         if remove_weight:
             layer.weight = torch.nn.Parameter(torch.empty(0), requires_grad=False)
-    elif ops._supports_onednn and (
-        current_platform.get_cpu_architecture() == CpuArchEnum.X86
-        or ops.is_onednn_acl_supported()
-    ):
+    elif ops._supports_onednn:
         origin_weight = layer.weight
         if remove_weight:
             layer.weight = torch.nn.Parameter(torch.empty(0), requires_grad=False)