Modify padding strategy: remove weight copy in fc padding (#21650)

test=develop

paddle/fluid/operators/math/fc.cc

@@ -30,8 +30,7 @@ class FCFunctor<platform::CPUDeviceContext, T> {
     auto blas = math::GetBlas<platform::CPUDeviceContext, T>(context);
     framework::Tensor Y1;
     T* Y1_data = nullptr;
-    auto padding = N % 128 == 0 && K % 128 == 0;
-    if (padding) {
+    if (padding_weights) {
       const int NN = N + 4;
       const int KK = K + 4;
       framework::Tensor X1;
@@ -43,25 +42,13 @@ class FCFunctor<platform::CPUDeviceContext, T> {
       for (int i = 0; i < M; i++) {
         memcpy(X1_data + i * KK, X + i * K, K * sizeof(T));
       }
-      framework::Tensor W1;
-      T* W1_data = nullptr;
-      if (!padding_weights) {
-        W1_data = W1.mutable_data<T>({(K + 4) * (N + 4)}, platform::CPUPlace());
-#ifdef PADDLE_WITH_MKLML
-#pragma omp parallel for
-#endif
-        for (int i = 0; i < K; i++) {
-          memcpy(W1_data + i * NN, W + i * N, N * sizeof(T));
-        }
-      }
-      blas.GEMM(false, false, M, N, K, static_cast<T>(1.0), X1_data, KK,
-                (padding_weights ? W : W1_data), NN, static_cast<T>(0.0),
-                Y1_data, NN);
+      blas.GEMM(false, false, M, N, K, static_cast<T>(1.0), X1_data, KK, W, NN,
+                static_cast<T>(0.0), Y1_data, NN);
     } else {
       blas.MatMul(M, N, K, X, W, Y);
     }
     if (B == NULL) {
-      if (padding) {
+      if (padding_weights) {
 #ifdef PADDLE_WITH_MKLML
 #pragma omp parallel for
 #endif
@@ -80,7 +67,7 @@ class FCFunctor<platform::CPUDeviceContext, T> {
               .At(N);
       for (int i = 0; i < M; i++) {
         T* dst = Y + i * N;
-        T* src = (padding) ? Y1_data + i * (N + 4) : dst;
+        T* src = (padding_weights) ? Y1_data + i * (N + 4) : dst;
         compute(B, src, dst, N);
       }
     } else {
@@ -92,7 +79,7 @@ class FCFunctor<platform::CPUDeviceContext, T> {
 #endif
       for (int i = 0; i < M; i++) {
         T* dst = Y + i * N;
-        T* src = (padding) ? Y1_data + i * (N + 4) : dst;
+        T* src = (padding_weights) ? Y1_data + i * (N + 4) : dst;
         compute(B, src, dst, N);
       }
     }