Revert "For Apple silicon, add separation between architecture and Metal API selection" (#101)

This seems to not work with some Mac versions, reverting for now.

Reverts #96

Author: Ahajha

mojo/extensions.bzl

@@ -201,16 +201,8 @@ _gpu_toolchains_tag = tag_class(
                 "mi325": "amdgpu:gfx942",
                 "mi355": "amdgpu:gfx950",
                 "rtx5090": "nvidia:120a",
-                "metal1": "metal:1",
-                "metal2": "metal:2",
-                "metal3": "metal:3",
-                "metal4": "metal:4",
-                "metal5": "metal:5",
-                "metal1_metal4": "metal:1-metal4",
-                "metal2_metal4": "metal:2-metal4",
-                "metal3_metal4": "metal:3-metal4",
-                "metal4_metal4": "metal:4-metal4",
-                "metal5_metal4": "metal:5-metal4",
+                "metal3": "metal:30",
+                "metal4": "metal:40",
             },
             doc = "The GPUs supported by this toolchain, mapping to Mojo's target accelerators.",
         ),
@@ -235,11 +227,8 @@ _gpu_toolchains_tag = tag_class(
                 "MI355": "mi355",
                 "Navi": "radeon",
                 "AMD Radeon Graphics": "radeon",
-                "Apple M1": "metal1",
-                "Apple M2": "metal2",
-                "Apple M3": "metal3",
-                "Apple M4": "metal4",
-                "Apple M5": "metal5",
+                "Metal 3": "metal3",
+                "Metal 4": "metal4",
             },
             doc = "The output from nvidia-smi or rocm-smi to the corresponding GPU name in SUPPORTED_GPUS.",
         ),

mojo/mojo_host_platform.bzl

@@ -87,13 +87,6 @@ def _get_amd_constraints_with_rocm_smi(rctx, rocm_smi, gpu_mapping):
 
     return constraints
 
-def _toolchain_supports_metal4(rctx):
-    result = rctx.execute(["/usr/bin/xcrun", "--sdk", "macosx", "--show-sdk-version"])
-    _log_result(rctx, "/usr/bin/xcrun --sdk macosx --show-sdk-version", result)
-    if result.return_code != 0:
-        return False
-    return int(result.stdout.strip().split(".")[0]) >= 26
-
 def _get_apple_constraint(rctx, gpu_mapping):
     result = rctx.execute(["/usr/bin/sw_vers", "--productVersion"])
     _log_result(rctx, "/usr/sbin/sw_vers --productVersion", result)
@@ -109,29 +102,21 @@ def _get_apple_constraint(rctx, gpu_mapping):
 
     _log_result(rctx, "/usr/sbin/system_profiler SPDisplaysDataType", result)
 
-    chipset_model = None
-    metal_support = None
+    metal_version = None
     for line in result.stdout.splitlines():
-        if "Chipset Model:" in line:
-            chipset_model = line
-        elif "Metal Support:" in line:
-            metal_support = line
+        if "Metal Support:" in line:
+            metal_version = line
+            break
 
-    if not chipset_model:  # macOS VMs may not have GPUs attached
+    if not metal_version:  # macOS VMs may not have GPUs attached
         return None
 
-    metal4 = (
-        metal_support and "Metal 4" in metal_support and
-        _toolchain_supports_metal4(rctx)
-    )
-
     for gpu_name, constraint in gpu_mapping.items():
-        if gpu_name in chipset_model:
-            if not constraint:
+        if gpu_name in metal_version:
+            if constraint:
+                return "@mojo_gpu_toolchains//:{}_gpu".format(constraint)
+            else:
                 return None
-            if metal4:
-                constraint += "_metal4"
-            return "@mojo_gpu_toolchains//:{}_gpu".format(constraint)
 
     _fail(rctx, "Unrecognized system_profiler output, please add it to your gpu_mapping in the MODULE.bazel file: {}".format(result.stdout))
     return None