[BE] Cleanup stale comments/copy from gemm (#162001)

malfet · pytorchmergebot · commit b40d9432be44 · 2025-09-03T14:31:09.000Z
Followup after #154012 Since the introduction of `gemm_no_downcast_stub` it's no longer necessary to allocate temporary array and then manually implement the `beta` logic in the codebase Pull Request resolved: #162001 Approved by: https://github.com/drisspg ghstack dependencies: #161999
diff --git a/aten/src/ATen/native/CPUBlas.cpp b/aten/src/ATen/native/CPUBlas.cpp
@@ -457,24 +457,9 @@ void gemm(
     return;
   }
 #endif
-  // for the fallback path, first compute gemm with beta = 0,
-  // and then add c in full precision.
-  int64_t c_size = n * m;
-  std::vector<float> float_c(c_size, 0.f);
   gemm_no_downcast_stub(
       at::kCPU, at::kBFloat16,
-      transa, transb, m, n, k, alpha, a, lda, b, ldb, 0.f, float_c.data(), m);
-  for (const auto j : c10::irange(n)) {
-    for (const auto i : c10::irange(m)) {
-      auto offset = j * ldc + i;
-      // beta == 0 won't propagate NaN from C
-      if (beta == 0.f) {
-        c[offset] = float_c[j * m + i];
-      } else {
-        c[offset] = beta * c[offset] + float_c[j * m + i];
-      }
-    }
-  }
+      transa, transb, m, n, k, alpha, a, lda, b, ldb, beta, c, ldc);
 }
 
 void gemm(
@@ -493,24 +478,9 @@ void gemm(
     return;
   }
 #endif
-  // for the fallback path, first compute gemm with beta = 0,
-  // and then add c in full precision.
-  int64_t c_size = n * m;
-  std::vector<float> float_c(c_size, 0.f);
   gemm_no_downcast_stub(
       at::kCPU, at::kHalf,
-      transa, transb, m, n, k, alpha, a, lda, b, ldb, 0.f, float_c.data(), m);
-  for (const auto j : c10::irange(n)) {
-    for (const auto i : c10::irange(m)) {
-      auto offset = j * ldc + i;
-      // beta == 0 won't propagate NaN from C
-      if (beta == 0.f) {
-        c[offset] = float_c[j * m + i];
-      } else {
-        c[offset] = beta * c[offset] + float_c[j * m + i];
-      }
-    }
-  }
+      transa, transb, m, n, k, alpha, a, lda, b, ldb, beta, c, ldc);
 }
 
 void gemm(
