add NULL=1 backend

tinygrad/runtime/ops_null.py

@@ -0,0 +1,17 @@
+from tinygrad.device import Compiled, Compiler, MallocAllocator, Renderer, Allocator
+
+class NullRenderer(Renderer):
+  def render(self, uops:list) -> str: return ""
+
+class NullProgram:
+  def __init__(self, name:str, lib:bytes): pass
+  def __call__(self, *bufs, global_size:tuple[int,int,int]=(1,1,1), local_size:tuple[int,int,int]=(1,1,1), vals:tuple[int, ...]=(), wait=False):
+    pass
+
+class NullAllocator(Allocator):
+  def _alloc(self, size, options): return "null"
+  def _copyin(self, dest, src:memoryview): pass
+  def _copyout(self, dest:memoryview, src): pass
+
+class NullDevice(Compiled):
+  def __init__(self, device:str): super().__init__(device, NullAllocator(), NullRenderer(), Compiler(), NullProgram)