[torch.compile] Disable recursive pre_grad_passes (#34092)

Signed-off-by: Richard Zou <zou3519@gmail.com>

vllm/envs.py

@@ -132,6 +132,7 @@ if TYPE_CHECKING:
     VLLM_DP_RANK_LOCAL: int = -1
     VLLM_DP_SIZE: int = 1
     VLLM_USE_STANDALONE_COMPILE: bool = True
+    VLLM_ENABLE_PREGRAD_PASSES: bool = False
     VLLM_DP_MASTER_IP: str = ""
     VLLM_DP_MASTER_PORT: int = 0
     VLLM_MOE_DP_CHUNK_SIZE: int = 256
@@ -568,6 +569,15 @@ environment_variables: dict[str, Callable[[], Any]] = {
         "VLLM_USE_STANDALONE_COMPILE", "1"
     )
     == "1",
+    # Inductor's pre-grad passes don't do anything for vLLM.
+    # The pre-grad passes get run even on cache-hit and negatively impact
+    # vllm cold compile times by O(1s)
+    # Can remove this after the following issue gets fixed
+    # https://github.com/pytorch/pytorch/issues/174502
+    "VLLM_ENABLE_PREGRAD_PASSES": lambda: os.environ.get(
+        "VLLM_ENABLE_PREGRAD_PASSES", "0"
+    )
+    == "1",
     # Debug pattern matching inside custom passes.
     # Should be set to the fx.Node name (e.g. 'getitem_34' or 'scaled_mm_3').
     "VLLM_PATTERN_MATCH_DEBUG": lambda: os.environ.get(