[torch.compile][Fusion] Fix attention fusion pass removing kv_udpate op. (#33945)

Signed-off-by: charlifu <charlifu@amd.com>

tests/compile/passes/test_fusion_attn.py

@@ -267,7 +267,7 @@ elif current_platform.is_rocm():
     PATTERN_TEST_MODELS_FP8 = [
         ("amd/Llama-3.1-8B-Instruct-FP8-KV", TestAttentionFp8StaticQuantPatternModel)
     ]
-    BACKENDS = [
+    BACKENDS_FP8 = [
         AttentionBackendEnum.ROCM_AITER_UNIFIED_ATTN,
         AttentionBackendEnum.ROCM_ATTN,
         AttentionBackendEnum.TRITON_ATTN,
@@ -474,6 +474,17 @@ def test_attention_quant_pattern(
     assert attn_nodes_pre[0].kwargs.get("output_block_scale") is None, (
         "Attention should not have output_block_scale before fusion"
     )
+
+    kv_cache_dummy_dep_pre_is_none = (
+        attn_nodes_pre[0].kwargs.get("kv_cache_dummy_dep") is None
+    )
+    kv_cache_dummy_dep_post_is_none = (
+        attn_nodes_post[0].kwargs.get("kv_cache_dummy_dep") is None
+    )
+    assert not (kv_cache_dummy_dep_pre_is_none ^ kv_cache_dummy_dep_post_is_none), (
+        "The kv_cache_dummy_dep should be consistent before and after fusion"
+    )
+
     if quant_key.dtype == FP8_DTYPE:
         assert attn_nodes_post[0].kwargs.get("output_block_scale") is None, (
             "Attention should not have output_block_scale after FP8 fusion"

vllm/compilation/passes/fusion/attn_quant_fusion.py

@@ -142,6 +142,7 @@ class AttentionFp8StaticQuantPattern(AttentionQuantPattern):
             v: torch.Tensor,
             output_attn: torch.Tensor,
             scale: torch.Tensor,
+            kv_cache_dummy_dep: torch.Tensor,
         ) -> torch.Tensor:
             at1 = auto_functionalized(
                 ATTN_OP,
@@ -152,6 +153,7 @@ class AttentionFp8StaticQuantPattern(AttentionQuantPattern):
                 layer_name=self.layer_name,
                 output_scale=None,
                 output_block_scale=None,
+                kv_cache_dummy_dep=kv_cache_dummy_dep,
             )
             attn_out_view = RESHAPE_OP(
                 at1[1], [q.shape[0], self.num_heads * self.head_size]
@@ -165,6 +167,7 @@ class AttentionFp8StaticQuantPattern(AttentionQuantPattern):
             v: torch.Tensor,
             output_attn: torch.Tensor,
             scale: torch.Tensor,
+            kv_cache_dummy_dep: torch.Tensor,
         ) -> torch.Tensor:
             # attn output in quant_dtype
             output_attn = torch.ops.aten.full.default(
@@ -182,6 +185,7 @@ class AttentionFp8StaticQuantPattern(AttentionQuantPattern):
                 layer_name=self.layer_name,
                 output_scale=scale,
                 output_block_scale=None,
+                kv_cache_dummy_dep=kv_cache_dummy_dep,
             )
             return RESHAPE_OP(at1[1], [-1, self.num_heads * self.head_size])
 
@@ -191,6 +195,7 @@ class AttentionFp8StaticQuantPattern(AttentionQuantPattern):
             self.empty(5, self.num_heads, self.head_size),  # v
             self.empty(5, self.num_heads, self.head_size),  # attn_output
             empty_fp32(1, 1),  # scale
+            self.empty(0),  # kv_cache_dummy_dep
         ]
 
         pm.register_replacement(
@@ -228,6 +233,7 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
             output_quant: torch.Tensor,
             output_scale: torch.Tensor,
             input_scale: torch.Tensor,
+            kv_cache_dummy_dep: torch.Tensor,
         ) -> tuple[torch.Tensor, torch.Tensor]:
             at1 = auto_functionalized(
                 ATTN_OP,
@@ -238,6 +244,7 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
                 layer_name=self.layer_name,
                 output_scale=None,
                 output_block_scale=None,
+                kv_cache_dummy_dep=kv_cache_dummy_dep,
             )
             attn_out_view = RESHAPE_OP(
                 at1[1], [q.shape[0], self.num_heads * self.head_size]
@@ -261,6 +268,7 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
             output_quant: torch.Tensor,
             output_scale: torch.Tensor,
             input_scale: torch.Tensor,
+            kv_cache_dummy_dep: torch.Tensor,
         ) -> tuple[torch.Tensor, torch.Tensor]:
             # attention output in quant_dtype
             output_attn = torch.ops.aten.full.default(
@@ -280,6 +288,7 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
                 layer_name=self.layer_name,
                 output_scale=input_scale,
                 output_block_scale=output_scale_view,
+                kv_cache_dummy_dep=kv_cache_dummy_dep,
             )
             output = RESHAPE_OP(at2[1], [-1, self.num_heads * self.head_size // 2])
             return output, at2[2]
@@ -294,6 +303,7 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
                 128, round_up(self.num_heads * self.head_size // 16, 4)
             ),  # output_scale
             empty_fp32(1, 1),  # input_scale
+            self.empty(0),  # kv_cache_dummy_dep
         ]
 
         pm.register_replacement(