[ROCm] Enable wvSplitK skinny GEMM kernel for RDNA4/gfx1x decode (#34709)

Signed-off-by: L.B.R. <lbr@mmonad.com>
Co-authored-by: L.B.R. <lbr@mmonad.com>

vllm/model_executor/layers/utils.py

@@ -122,7 +122,7 @@ def use_aiter_triton_gemm(n, m, k, dtype):
 def rocm_unquantized_gemm_impl(
     x: torch.Tensor, weight: torch.Tensor, bias: torch.Tensor | None = None
 ) -> torch.Tensor:
-    from vllm.platforms.rocm import on_gfx9, on_gfx950
+    from vllm.platforms.rocm import on_gfx1x, on_gfx9, on_gfx950
 
     n = x.numel() // x.size(-1)
     m = weight.shape[0]
@@ -169,12 +169,12 @@ def rocm_unquantized_gemm_impl(
 
     use_skinny = (
         envs.VLLM_ROCM_USE_SKINNY_GEMM
-        and on_gfx9()
+        and (on_gfx9() or on_gfx1x())
         and x.dtype in [torch.float16, torch.bfloat16]
         and k % 8 == 0
     )
 
-    if use_skinny is not True:
+    if not use_skinny:
         return torch.nn.functional.linear(x, weight, bias)
 
     x_view = x.reshape(-1, x.size(-1))