[Hardware][Apple] Native support for macOS Apple Silicon (#11696)

Signed-off-by: Wallas Santos <wallashss@ibm.com>
Co-authored-by: Michael Goin <michael@neuralmagic.com>

vllm/config.py

@@ -4,6 +4,7 @@ import enum
 import hashlib
 import json
 import os
+import sys
 import warnings
 from contextlib import contextmanager
 from dataclasses import dataclass, field, replace
@@ -2259,6 +2260,17 @@ def _get_and_verify_dtype(
                     "supported for POWERPC.")
                 torch_dtype = torch.bfloat16
 
+            # TODO: change this condition to check if the platform support bf16
+            # instead of checking the OS. For instance M2 shall supports bf16
+            # already. But we need to modify `cpu_extension.cmake` to activate
+            # the feature in the build.
+            if (current_platform.is_cpu() and sys.platform.startswith("darwin")
+                    and current_platform.get_cpu_architecture()
+                    == CpuArchEnum.ARM and config_dtype == torch.bfloat16):
+                logger.info("For macOS with Apple Silicon, currently bfloat16 "
+                            "is not supported. Setting dtype to float16.")
+                torch_dtype = torch.float16
+
             if current_platform.is_hpu() and config_dtype == torch.float16:
                 logger.info(
                     "For HPU, we cast models to bfloat16 instead of"