Fix torch.compile issue for LLM.int8() with threshold=0 (#1581)

Author: matthewdouglas

bitsandbytes/autograd/_functions.py

@@ -84,6 +84,13 @@ def get_inverse_transform_indices(
     return permuted_tile_indices
 
 
+# torch.compiler.is_compiling() is available only in torch >= 2.3
+if hasattr(torch.compiler, "is_compiling"):
+    _is_compiling = torch.compiler.is_compiling
+else:
+    _is_compiling = torch._dynamo.is_compiling
+
+
 @deprecated(
     "This function is deprecated and will be removed in a future release.",
     category=FutureWarning,
@@ -174,7 +181,7 @@ def forward(
         input_shape = A.shape
 
         # Cast A to fp16
-        if A.dtype != torch.float16:
+        if A.dtype != torch.float16 and not _is_compiling():
             warnings.warn(f"MatMul8bitLt: inputs will be cast from {A.dtype} to float16 during quantization")
 
         if len(A.shape) == 3: