[Fix] Add torch compile for torch.clamp back (sgl-project#4936)

Author: Fridge003

python/sglang/srt/model_executor/forward_batch_info.py

@@ -39,6 +39,7 @@
 import triton.language as tl
 
 from sglang.srt.layers.rotary_embedding import MRotaryEmbedding
+from sglang.srt.utils import get_compiler_backend
 
 if TYPE_CHECKING:
     from sglang.srt.layers.attention.base_attn_backend import AttentionBackend
@@ -299,7 +300,7 @@ def init_new(
         # Init position information
         if ret.forward_mode.is_decode():
             if ret.positions is None:
-                ret.positions = torch.clamp((batch.seq_lens - 1), min=0).to(torch.int64)
+                ret.positions = clamp_position(batch.seq_lens)
         else:
             ret.extend_seq_lens = torch.tensor(
                 batch.extend_seq_lens, dtype=torch.int32
@@ -519,3 +520,8 @@ def compute_position_torch(
     extend_start_loc = torch.zeros_like(extend_seq_lens)
     extend_start_loc[1:] = torch.cumsum(extend_seq_lens[:-1], dim=0)
     return positions.to(torch.int64), extend_start_loc
+
+
+@torch.compile(dynamic=True, backend=get_compiler_backend())
+def clamp_position(seq_lens):
+    return torch.clamp((seq_lens - 1), min=0).to(torch.int64)