x64: brgemm bwd_w convolution: update scratchpad data preparing

src/cpu/x64/jit_brgemm_conv_bwd_w.cpp

@@ -1375,15 +1375,26 @@ void brgemm_convolution_bwd_weights_t::prepare_scratchpad_data(
     const auto &jcp = pd()->jcp_;
 
     auto tr_src = scratchpad.template get<src_data_t>(key_conv_tr_src);
-    // Zero out guard elements that cross a buffer boundary to prevent a
-    // race condition due to buffer overflows from memory optimization where
-    // buffers sharing padding
-    // TODO: optimize it
-    for (size_t isb = 1; isb <= jcp.tr_src_buf_count; ++isb) {
-        src_data_t *ts
-                = &tr_src[isb * jcp.tr_src_buf_size * jcp.nb_ic_blocking];
-        for (int i = 0; i < jcp.tr_src_num_guard_elems; ++i)
-            ts[i] = 0;
+    const auto tr_src_full_size = jcp.tr_src_buf_size * jcp.nb_ic_blocking;
+    if (jcp.oh_block < jcp.oh || jcp.id > 1) {
+        // if (oh_block < oh) or (id > 1) then we zero all buffer because last
+        // elements position may vary depending on position of od_s, oh_block,
+        // padding and kh
+        parallel_nd(jcp.tr_src_buf_count, [&](size_t isb) {
+            src_data_t *ts = &tr_src[isb * tr_src_full_size];
+            std::memset(ts, 0, jcp.src_dsz * tr_src_full_size);
+        });
+        // Zero out last guard elements
+        src_data_t *ts = &tr_src[jcp.tr_src_buf_count * tr_src_full_size];
+        std::memset(ts, 0, jcp.src_dsz * jcp.tr_src_num_guard_elems);
+    } else {
+        // Zero out guard elements that cross a buffer boundary to prevent a
+        // race condition due to buffer overflows from memory optimization where
+        // buffers sharing padding
+        parallel_nd(jcp.tr_src_buf_count, [&](size_t isb) {
+            src_data_t *ts = &tr_src[(isb + 1) * tr_src_full_size];
+            std::memset(ts, 0, jcp.src_dsz * jcp.tr_src_num_guard_elems);
+        });
     }
 
     if (jcp.global_transpose && jcp.nthr_oc_b > 1) {