Add autoconfig of GCC/Clang arch flags; DMOJ#303

Author: Xyene

.arm.test.py

@@ -12,10 +12,8 @@
 
 
 def main():
-    judgeenv.env['runtime'] = {
-        'clang_target_arch': None,  # Clang can't autodetect march=native
-    }
-    judgeenv.env['extra_fs'] = {};
+    judgeenv.env['runtime'] = {}
+    judgeenv.env['extra_fs'] = {}
 
     logging.basicConfig(level=logging.INFO)
 

dmoj/executors/gcc_executor.py

@@ -100,6 +100,26 @@ def get_march_flag(cls):
     def get_version_flags(cls, command):
         return ['-dumpversion']
 
+    @classmethod
+    def autoconfig_run_test(cls, result):
+        # Some versions of GCC/Clang (like those in Raspbian or ARM64 Debian)
+        # can't autodetect the CPU, in which case our unconditional passing of
+        # -march=native breaks. Here we try to see if -march=native works, and
+        # if not fall back to a generic (slow) build.
+        for target in ['native', None]:
+            result[cls.arch] = target
+            executor = type('Executor', (cls,), {'runtime_dict': result})
+            executor.__module__ = cls.__module__
+            errors = []
+            success = executor.run_self_test(output=False, error_callback=errors.append)
+            if success:
+                message = 'Using %s (%s target)' % (result[cls.command], target or 'generic')
+                # Don't pollute the YAML in the default case
+                if target == 'native':
+                    del result[cls.arch]
+                return result, success, message, None
+        return result, success, 'Failed self-test', '\n'.join(errors)
+
     @classmethod
     def autoconfig(cls):
         return super(GCCExecutor, cls).autoconfig()