simplify parsing the gemm operator

src/onnx/onnx.cpp

@@ -481,22 +481,20 @@ struct onnx_parser
         auto l2 = (transb) ? prog.add_instruction(op::transpose{perm}, args[1]) : args[1];
         if(args.size() == 3)
         {
-            if(beta != 0.f)
+            if(beta != 0.f && args[2]->get_shape().elements() > 0)
             {
-                auto l3 = prog.add_instruction(op::dot{alpha}, l1, l2);
-                auto l4 = args[2];
-                if(l4->get_shape().scalar()) // ignore args[2] (no C value added to alpha*A*B)
-                    return l3;
-                if(beta != 1.f)
+                auto out_lens = l1->get_shape().lens();
+                out_lens.back() = l2->get_shape().lens().back();
+                auto l3 = args[2];
+                if (!std::equal(out_lens.begin(), out_lens.end(), args[2]->get_shape().lens().begin()))
                 {
-                    auto beta_val = prog.add_literal(beta);
-                    auto l5 = prog.add_instruction(op::scalar{args[2]->get_shape()}, beta_val);
-                    l4      = prog.add_instruction(op::mul{}, args[2], l5);
+                    l3 = prog.add_instruction(op::multibroadcast{out_lens}, args[2]);
                 }
-                return add_broadcastable_binary_op(l3, l4, op::add{});
+
+                return prog.add_instruction(op::dot{alpha, beta}, l1, l2, l3);
             }
         }
-        return prog.add_instruction(op::dot{alpha, beta}, l1, l2);
+        return prog.add_instruction(op::dot{alpha}, l1, l2);
     }
 
     instruction_ref

test/onnx/onnx_test.cpp

@@ -580,14 +580,8 @@ TEST_CASE(gemm_ex)
     auto l2     = p.add_parameter("3", migraphx::shape{migraphx::shape::float_type, {1, 1, 6, 7}});
     auto t0     = p.add_instruction(migraphx::op::transpose{{0, 1, 3, 2}}, l0);
     auto alpha  = 0.5f;
-    auto res_ab = p.add_instruction(migraphx::op::dot{alpha}, t0, l1);
-
-    auto beta       = 0.8f;
-    auto l_beta     = p.add_literal(beta);
-    auto brcst_beta = p.add_instruction(migraphx::op::scalar{l2->get_shape()}, l_beta);
-    auto res_c      = p.add_instruction(migraphx::op::mul{}, l2, brcst_beta);
-    p.add_instruction(migraphx::op::add{}, res_ab, res_c);
-
+    auto beta   = 0.8f;
+    p.add_instruction(migraphx::op::dot{alpha, beta}, t0, l1, l2);
     auto prog = migraphx::parse_onnx("gemm_test_ex.onnx");
 
     EXPECT(p == prog);