More if-constexpr (#4054)

Summary:
Pull Request resolved: #4054

X-link: facebookresearch/FBGEMM#1139

- Update more locations to if-constexpr to accomodate D73473546

Reviewed By: spcyppt

Differential Revision: D73873544

fbshipit-source-id: 8fbdb7f63cc66c75b775ae33b4ec69f88ca6ad2c

Author: q10

fbgemm_gpu/codegen/training/backward/embedding_backward_split_indice_weights_template.cu

@@ -122,7 +122,7 @@ __global__ __launch_bounds__(kForwardMaxThreads) void
     const auto D_end = D_offsets[t + 1];
     const auto D = D_end - D_start;
     auto D_emb = D;
-    if (std::is_same<emb_t, uint8_t>::value) {
+    if constexpr (std::is_same_v<emb_t, uint8_t>) {
       D_emb += kINT8QparamsBytes;
     }
     const auto indices_start = offsets[b_t];

fbgemm_gpu/codegen/training/forward/embedding_forward_split_kernel_nobag_small_template.cu

@@ -124,7 +124,7 @@ batch_index_select_dim0_codegen_forward_small_kernel(
     {%- endif %}
 
     int32_t D_emb = D;
-    if (std::is_same<emb_t, uint8_t>::value) {
+    if constexpr (std::is_same_v<emb_t, uint8_t>) {
         D_emb += kINT8QparamsBytes;
     }
 

fbgemm_gpu/codegen/training/forward/embedding_forward_split_kernel_template.cu

@@ -730,7 +730,7 @@ batch_index_select_dim0_codegen_forward_kernel(
     // D is computed in the bag case or provided as function arg in the nobag case
     // (nobag only supports the case where the embedding dimensions are the same for all tables)
     int32_t D_emb = D;
-    if (std::is_same<emb_t, uint8_t>::value) {
+    if constexpr (std::is_same_v<emb_t, uint8_t>) {
         D_emb += kINT8QparamsBytes;
     }
 

fbgemm_gpu/src/split_embeddings_cache/lxu_cache.cu

@@ -66,7 +66,7 @@ __global__ __launch_bounds__(kMaxThreads) void lxu_cache_flush_kernel(
             threadIdx.x);
 
     float2 qparams;
-    if (std::is_same<emb_t, uint8_t>::value) {
+    if constexpr (std::is_same_v<emb_t, uint8_t>) {
       qparams =
           thrust_find_qparams<cache_t>(&lxu_cache_weights[b][0], D_current);
       if (threadIdx.x == 0) {