[Impeller] Turns on the Metal validator for impeller_unittests.

testing/run_tests.py

@@ -138,6 +138,16 @@ def is_mac():
   return sys.platform == 'darwin'
 
 
+def is_aarm64():
+  assert is_mac()
+  output = subprocess.check_output(['sysctl', 'machdep.cpu'])
+  text = output.decode('utf-8')
+  aarm64 = text.find('Apple') >= 0
+  if not aarm64:
+    assert text.find('GenuineIntel') >= 0
+  return aarm64
+
+
 def is_linux():
   return sys.platform.startswith('linux')
 
@@ -467,25 +477,30 @@ def make_test(name, flags=None, extra_env=None):
         shuffle_flags,
         coverage=coverage
     )
+    extra_env = {
+        # pylint: disable=line-too-long
+        # See https://developer.apple.com/documentation/metal/diagnosing_metal_programming_issues_early?language=objc
+        'MTL_SHADER_VALIDATION': '1',  # Enables all shader validation tests.
+        'MTL_SHADER_VALIDATION_GLOBAL_MEMORY':
+            '1',  # Validates accesses to device and constant memory.
+        'MTL_SHADER_VALIDATION_THREADGROUP_MEMORY':
+            '1',  # Validates accesses to threadgroup memory.
+        'MTL_SHADER_VALIDATION_TEXTURE_USAGE':
+            '1',  # Validates that texture references are not nil.
+    }
+    if is_aarm64():
+      extra_env.append({
+          'METAL_DEBUG_ERROR_MODE': '0',  # Enables metal validation.
+          'METAL_DEVICE_WRAPPER_TYPE': '1',  # Enables metal validation.
+      })
     # Impeller tests are only supported on macOS for now.
     run_engine_executable(
         build_dir,
         'impeller_unittests',
         executable_filter,
         shuffle_flags,
         coverage=coverage,
-        extra_env={
-            # pylint: disable=line-too-long
-            # See https://developer.apple.com/documentation/metal/diagnosing_metal_programming_issues_early?language=objc
-            'MTL_SHADER_VALIDATION':
-                '1',  # Enables all shader validation tests.
-            'MTL_SHADER_VALIDATION_GLOBAL_MEMORY':
-                '1',  # Validates accesses to device and constant memory.
-            'MTL_SHADER_VALIDATION_THREADGROUP_MEMORY':
-                '1',  # Validates accesses to threadgroup memory.
-            'MTL_SHADER_VALIDATION_TEXTURE_USAGE':
-                '1',  # Validates that texture references are not nil.
-        },
+        extra_env=extra_env,
         # TODO(117122): Remove this allowlist.
         # https://github.com/flutter/flutter/issues/114872
         allowed_failure_output=[