auto detect, test and run with clang++ for SourceBuilder

python/taichi/lang/__init__.py

@@ -25,7 +25,7 @@
 from taichi.lang.type_factory_impl import type_factory
 from taichi.lang.util import (has_pytorch, is_taichi_class, python_scope,
                               taichi_scope, to_numpy_type, to_pytorch_type,
-                              to_taichi_type)
+                              to_taichi_type, has_clangpp)
 from taichi.misc.util import deprecated
 from taichi.snode.fields_builder import FieldsBuilder
 

python/taichi/lang/source_builder.py

@@ -5,6 +5,7 @@
 
 from taichi.lang.exception import TaichiSyntaxError
 from taichi.lang.ops import asm, bitcode_func_call, external_func_call
+from taichi.lang.util import get_clangpp
 
 
 class SourceBuilder():
@@ -16,7 +17,7 @@ def __init__(self, source, mode='bc'):
             self.compiled_file = os.path.join(self.td, 'source.bc')
             with open(self.source_file, 'w') as f:
                 f.write(source)
-            os.system('clang++-11 -flto -c ' + self.source_file + ' -o ' +
+            os.system(get_clangpp() + ' -flto -c ' + self.source_file + ' -o ' +
                       self.compiled_file)
             self.bc = self.compiled_file
         elif self.mode == 'so':

python/taichi/lang/util.py

@@ -28,6 +28,18 @@ def has_pytorch():
     return _has_pytorch
 
 
+from distutils.spawn import find_executable
+_clangpp_candidates = ['clang++-8', 'clang++-10', 'clang++-11', 'clang++-12', 'clang++']
+_clangpp_presence = None
+for c in _clangpp_candidates:
+    if find_executable(c) is not None:
+        _clangpp_presence = find_executable(c)
+def has_clangpp():
+    return _clangpp_presence is not None
+def get_clangpp():
+    return _clangpp_presence
+
+
 def is_taichi_class(rhs):
     taichi_class = False
     try:

tests/python/test_external_func.py

@@ -40,6 +40,7 @@ def func_so() -> ti.i32:
     assert func_so() == 11**8
 
 
+@pytest.mark.skipif(not ti.has_clangpp(), reason='Clang not installed.')
 @ti.test(arch=[ti.cpu, ti.cuda])
 def test_source_builder_bc():
     source_bc = '''