Avoid undefined symbol error when building AdIndexer LTO (#19009)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19009

Move the definition of `MulFunctor<>::Backward()` into a header file.

Reviewed By: BIT-silence

Differential Revision: D14823230

fbshipit-source-id: 1efaec01863fcc02dcbe7e788d376e72f8564501

2 files changed, 81 insertions, 81 deletions

diff --git a/caffe2/operators/elementwise_mul_gradient_op.cc b/caffe2/operators/elementwise_mul_gradient_op.cc
index cbc73660d6..5065504349 100644
--- a/caffe2/operators/elementwise_mul_gradient_op.cc
+++ b/caffe2/operators/elementwise_mul_gradient_op.cc
@@ -7,87 +7,6 @@
 
 namespace caffe2 {
 
-namespace {
-
-template <typename TGrad, typename TIn>
-void ComputeMulGradient(
-    const int ndim,
-    const int* A_dims,
-    const int* B_dims,
-    const int* C_dims,
-    const TGrad* dC,
-    const TIn* A,
-    const TIn* B,
-    TGrad* dA,
-    TGrad* dB,
-    CPUContext* context) {
-  const int A_size =
-      std::accumulate(A_dims, A_dims + ndim, 1, std::multiplies<int>());
-  const int B_size =
-      std::accumulate(B_dims, B_dims + ndim, 1, std::multiplies<int>());
-  const int C_size =
-      std::accumulate(C_dims, C_dims + ndim, 1, std::multiplies<int>());
-  math::Set<TGrad, CPUContext>(A_size, TGrad(0), dA, context);
-  math::Set<TGrad, CPUContext>(B_size, TGrad(0), dB, context);
-  std::vector<int> index(ndim, 0);
-  for (int C_index = 0; C_index < C_size; ++C_index) {
-    const int A_index =
-        math::utils::GetIndexFromDims(ndim, A_dims, index.data());
-    const int B_index =
-        math::utils::GetIndexFromDims(ndim, B_dims, index.data());
-    dA[A_index] += dC[C_index] * B[B_index];
-    dB[B_index] += dC[C_index] * A[A_index];
-    math::utils::IncreaseIndexInDims(ndim, C_dims, index.data());
-  }
-}
-
-} // namespace
-
-template <>
-template <typename TGrad, typename TIn, typename TOut>
-bool MulFunctor<CPUContext>::Backward(
-    const std::vector<int>& A_dims,
-    const std::vector<int>& B_dims,
-    const TGrad* dC,
-    const TIn* A,
-    const TIn* B,
-    const TOut* /* C */,
-    TGrad* dA,
-    TGrad* dB,
-    CPUContext* context) const {
-  if (A_dims == B_dims) {
-    const int size = std::accumulate(
-        A_dims.cbegin(), A_dims.cend(), 1, std::multiplies<int>());
-    math::Mul(size, dC, B, dA, context);
-    math::Mul(size, dC, A, dB, context);
-    return true;
-  }
-  const int ndim = std::max(A_dims.size(), B_dims.size());
-  std::vector<int> A_broadcast_dims(ndim);
-  std::vector<int> B_broadcast_dims(ndim);
-  std::vector<int> C_broadcast_dims(ndim);
-  math::utils::ComputeBroadcastBinaryOpDims(
-      A_dims.size(),
-      A_dims.data(),
-      B_dims.size(),
-      B_dims.data(),
-      A_broadcast_dims.data(),
-      B_broadcast_dims.data(),
-      C_broadcast_dims.data());
-  ComputeMulGradient<TGrad, TIn>(
-      ndim,
-      A_broadcast_dims.data(),
-      B_broadcast_dims.data(),
-      C_broadcast_dims.data(),
-      dC,
-      A,
-      B,
-      dA,
-      dB,
-      context);
-  return true;
-}
-
 REGISTER_CPU_OPERATOR(
     MulGradient,
     BinaryElementwiseGradientOp<
diff --git a/caffe2/operators/elementwise_mul_op.h b/caffe2/operators/elementwise_mul_op.h
index f1c42edc48..6b31fe3684 100644
--- a/caffe2/operators/elementwise_mul_op.h
+++ b/caffe2/operators/elementwise_mul_op.h
@@ -8,6 +8,42 @@
 
 namespace caffe2 {
 
+namespace {
+
+template <typename TGrad, typename TIn>
+void ComputeMulGradient(
+    const int ndim,
+    const int* A_dims,
+    const int* B_dims,
+    const int* C_dims,
+    const TGrad* dC,
+    const TIn* A,
+    const TIn* B,
+    TGrad* dA,
+    TGrad* dB,
+    CPUContext* context) {
+  const int A_size =
+      std::accumulate(A_dims, A_dims + ndim, 1, std::multiplies<int>());
+  const int B_size =
+      std::accumulate(B_dims, B_dims + ndim, 1, std::multiplies<int>());
+  const int C_size =
+      std::accumulate(C_dims, C_dims + ndim, 1, std::multiplies<int>());
+  math::Set<TGrad, CPUContext>(A_size, TGrad(0), dA, context);
+  math::Set<TGrad, CPUContext>(B_size, TGrad(0), dB, context);
+  std::vector<int> index(ndim, 0);
+  for (int C_index = 0; C_index < C_size; ++C_index) {
+    const int A_index =
+        math::utils::GetIndexFromDims(ndim, A_dims, index.data());
+    const int B_index =
+        math::utils::GetIndexFromDims(ndim, B_dims, index.data());
+    dA[A_index] += dC[C_index] * B[B_index];
+    dB[B_index] += dC[C_index] * A[A_index];
+    math::utils::IncreaseIndexInDims(ndim, C_dims, index.data());
+  }
+}
+
+} // namespace
+
 template <class Context>
 struct MulFunctor {
   template <typename TIn, typename TOut>
@@ -43,6 +79,51 @@ struct MulFunctor {
       Context* context) const;
 };
 
+template <>
+template <typename TGrad, typename TIn, typename TOut>
+bool MulFunctor<CPUContext>::Backward(
+    const std::vector<int>& A_dims,
+    const std::vector<int>& B_dims,
+    const TGrad* dC,
+    const TIn* A,
+    const TIn* B,
+    const TOut* /* C */,
+    TGrad* dA,
+    TGrad* dB,
+    CPUContext* context) const {
+  if (A_dims == B_dims) {
+    const int size = std::accumulate(
+        A_dims.cbegin(), A_dims.cend(), 1, std::multiplies<int>());
+    math::Mul(size, dC, B, dA, context);
+    math::Mul(size, dC, A, dB, context);
+    return true;
+  }
+  const int ndim = std::max(A_dims.size(), B_dims.size());
+  std::vector<int> A_broadcast_dims(ndim);
+  std::vector<int> B_broadcast_dims(ndim);
+  std::vector<int> C_broadcast_dims(ndim);
+  math::utils::ComputeBroadcastBinaryOpDims(
+      A_dims.size(),
+      A_dims.data(),
+      B_dims.size(),
+      B_dims.data(),
+      A_broadcast_dims.data(),
+      B_broadcast_dims.data(),
+      C_broadcast_dims.data());
+  ComputeMulGradient<TGrad, TIn>(
+      ndim,
+      A_broadcast_dims.data(),
+      B_broadcast_dims.data(),
+      C_broadcast_dims.data(),
+      dC,
+      A,
+      B,
+      dA,
+      dB,
+      context);
+  return true;
+}
+
 } // namespace caffe2
 
 #endif // CAFFE2_OPERATORS_ELEMENTWISE_MUL_OP_H_