misc: Fix persistent kernel compilation

include/flashinfer/attention/persistent.cuh

@@ -138,6 +138,37 @@ __device__ __forceinline__ void write_o_(float (*o_frag)[KTraits::NUM_MMA_D_VO][
   }
 }
 
+template <typename KTraits>
+__device__ __forceinline__ void normalize_d(float (*o_frag)[KTraits::NUM_MMA_D_VO][8],
+                                            typename KTraits::DTypeQKAccum (*m)[2], float (*d)[2]) {
+  using AttentionVariant = typename KTraits::AttentionVariant;
+  if constexpr (AttentionVariant::use_softmax) {
+    float d_rcp[KTraits::NUM_MMA_Q][2];
+    // compute reciprocal of d
+#pragma unroll
+    for (uint32_t mma_q = 0; mma_q < KTraits::NUM_MMA_Q; ++mma_q) {
+#pragma unroll
+      for (uint32_t j = 0; j < 2; ++j) {
+        d_rcp[mma_q][j] = (m[mma_q][j] != typename KTraits::DTypeQKAccum(-math::inf))
+                              ? math::ptx_rcp(d[mma_q][j])
+                              : 0.f;
+      }
+    }
+
+#pragma unroll
+    for (uint32_t mma_q = 0; mma_q < KTraits::NUM_MMA_Q; ++mma_q) {
+#pragma unroll
+      for (uint32_t mma_d = 0; mma_d < KTraits::NUM_MMA_D_VO; ++mma_d) {
+#pragma unroll
+        for (uint32_t reg_id = 0; reg_id < 8; ++reg_id) {
+          o_frag[mma_q][mma_d][reg_id] =
+              o_frag[mma_q][mma_d][reg_id] * d_rcp[mma_q][(reg_id >> 1) & 1];
+        }
+      }
+    }
+  }
+}
+
 template <typename KTraits_, typename Params_>
 struct BlockBatchPagedAttentionPersistent {
   using KTraits = KTraits_;