From eef5f3e3430af641557567d16e3aa624497f059f Mon Sep 17 00:00:00 2001
From: Neo Zhang <zhang.jianyu@outlook.com>
Date: Fri, 7 Aug 2026 13:17:56 +0800
Subject: [PATCH] sycl : fix error Error OP FLASH_ATTN_EXT on arc770 (#26441)

---
 ggml/src/ggml-sycl/fattn-vec.hpp | 34 +++++++++++++++++---------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/ggml/src/ggml-sycl/fattn-vec.hpp b/ggml/src/ggml-sycl/fattn-vec.hpp
index 04baac4414..53ad0eaee4 100644
--- a/ggml/src/ggml-sycl/fattn-vec.hpp
+++ b/ggml/src/ggml-sycl/fattn-vec.hpp
@@ -73,6 +73,7 @@ static void flash_attn_ext_vec(const char* __restrict__ Q,
                         const int32_t nb31,
                         const int32_t nb32,
                         const int64_t nb33) {
+
 #ifdef SYCL_FLASH_ATTN
     // Skip unused kernel variants for faster compilation:
 
@@ -469,7 +470,6 @@ static void flash_attn_ext_vec(const char* __restrict__ Q,
         }
     }
 
-
     item_ct1.barrier(sycl::access::fence_space::local_space);
 
 #pragma unroll
@@ -591,22 +591,24 @@ void ggml_sycl_flash_attn_ext_vec_case_impl(ggml_backend_sycl_context & ctx, ggm
 
     const auto arch = ggml_sycl_info().devices[ctx.device].hw_info.arch;
     const int nthreads = ggml_sycl_fattn_vec_get_nthreads_device(arch);
-    // 256 threads would overflow the 64 KB work-group local memory at D == 512, so keep 128 there.
-    if (D <= 256 && nthreads == 256) {
-        constexpr int nthreads_hw = 256;
-        constexpr int nwarps = nthreads_hw / warp_size;
-        launch_fattn<D, cols_per_block, 1,
-                     flash_attn_ext_vec<D, cols_per_block, type_K, type_V,
-                                        use_logit_softcap, warp_size, nthreads_hw>, warp_size>(
-            ctx, dst, nwarps, nbytes_shared, D, need_f16_K, need_f16_V, false);
-    } else {
-        constexpr int nthreads_hw = 128;
-        constexpr int nwarps = nthreads_hw / warp_size;
-        launch_fattn<D, cols_per_block, 1,
-                     flash_attn_ext_vec<D, cols_per_block, type_K, type_V,
-                                        use_logit_softcap, warp_size, nthreads_hw>, warp_size>(
-            ctx, dst, nwarps, nbytes_shared, D, need_f16_K, need_f16_V, false);
+    if constexpr (D <= 256) {
+        if (nthreads == 256) {
+            constexpr int nthreads_hw = 256;
+            constexpr int nwarps = nthreads_hw / warp_size;
+            launch_fattn<D, cols_per_block, 1,
+                         flash_attn_ext_vec<D, cols_per_block, type_K, type_V,
+                                            use_logit_softcap, warp_size, nthreads_hw>, warp_size>(
+                ctx, dst, nwarps, nbytes_shared, D, need_f16_K, need_f16_V, false);
+            return;
+        }
     }
+
+    constexpr int nthreads_hw = 128;
+    constexpr int nwarps = nthreads_hw / warp_size;
+    launch_fattn<D, cols_per_block, 1,
+                 flash_attn_ext_vec<D, cols_per_block, type_K, type_V,
+                                    use_logit_softcap, warp_size, nthreads_hw>, warp_size>(
+        ctx, dst, nwarps, nbytes_shared, D, need_f16_K, need_f16_V, false);
 }
 
 template <int D, int type_K, int type_V>