[Bugfix][Quantization] Ensure input contiguity in per_token_quant_int8 (#31637)

Signed-off-by: vensen <vensenmu@gmail.com>

vllm/model_executor/layers/quantization/utils/int8_utils.py

@@ -122,15 +122,17 @@ def _per_token_quant_int8(
 
 
 def per_token_quant_int8(x):
+    original_shape = x.shape
+    if x.dim() > 2:
+        x = x.view(-1, original_shape[-1])
     M = x.numel() // x.shape[-1]
     N = x.shape[-1]
-    x_q = torch.empty_like(x, device=x.device, dtype=torch.int8)
-    scales = torch.empty(x.shape[:-1] + (1,), device=x.device, dtype=torch.float32)
+    x_q = torch.empty((M, N), device=x.device, dtype=torch.int8)
+    scales = torch.empty((M, 1), device=x.device, dtype=torch.float32)
     BLOCK = triton.next_power_of_2(N)
     # heuristics for number of warps
     num_warps = min(max(BLOCK // 256, 1), 8)
-
-    assert x.is_contiguous()
+    x = x.contiguous()
     _per_token_quant_int8[(M,)](
         x,
         x_q,
@@ -142,7 +144,8 @@ def per_token_quant_int8(x):
         num_warps=num_warps,
         num_stages=1,
     )
-
+    x_q = x_q.view(*original_shape)
+    scales = scales.view(*original_shape[:-1], 1)
     return x_q, scales