[torch.compile] transparent compilation with more logging (#12246)

Signed-off-by: youkaichao <youkaichao@gmail.com>

vllm/compilation/wrapper.py

@@ -9,6 +9,9 @@ import torch
 
 import vllm.envs as envs
 from vllm.config import CompilationLevel, get_current_vllm_config
+from vllm.logger import init_logger
+
+logger = init_logger(__name__)
 
 
 class TorchCompileWrapperWithCustomDispatcher:
@@ -82,6 +85,25 @@ class TorchCompileWrapperWithCustomDispatcher:
             return
 
         self.compiled_codes.append(new_code)
+        local_cache_dir = self.vllm_config.compilation_config.local_cache_dir
+        if isinstance(local_cache_dir, str):
+            decompiled_file = os.path.join(local_cache_dir,
+                                           "transformed_code.py")
+            if not os.path.exists(decompiled_file):
+                try:
+                    # usually the decompilation will succeed for most models,
+                    # as we guarantee a full-graph compilation in Dynamo.
+                    # but there's no 100% guarantee, since decompliation is
+                    # not a reversible process.
+                    import depyf
+                    src = depyf.decompile(new_code)
+                    with open(decompiled_file, "w") as f:
+                        f.write(src)
+
+                    logger.debug("Dynamo transformed code saved to %s",
+                                 decompiled_file)
+                except Exception:
+                    pass
 
         if self.vllm_config.compilation_config.use_cudagraph and \
             "update" in new_code.co_names: