Support Half/BFloat16 in hardtanh (#7899)

Partial fix for #7748.

Author: swolchok

kernels/portable/cpu/op_hardtanh.cpp

@@ -46,7 +46,7 @@ Tensor& hardtanh_out(
 
   ET_KERNEL_CHECK(ctx, in_type == out_type, InvalidArgument, out);
 
-  ET_SWITCH_REAL_TYPES(in_type, ctx, "hardtanh.out", CTYPE, [&]() {
+  ET_SWITCH_REALHBF16_TYPES(in_type, ctx, "hardtanh.out", CTYPE, [&]() {
     CTYPE min_casted;
     ET_SWITCH_SCALAR_OBJ_TYPES(min_type, ctx, "hardtanh.out", CTYPE_MIN, [&]() {
       CTYPE_MIN min_val;

kernels/portable/cpu/util/math_util.h

@@ -96,8 +96,10 @@ INT_T max_override(INT_T a, INT_T b) {
 
 template <
     typename T,
-    typename std::enable_if<std::is_same<T, exec_aten::Half>::value, bool>::
-        type = true>
+    typename std::enable_if_t<
+        std::is_same_v<T, exec_aten::Half> ||
+            std::is_same_v<T, exec_aten::BFloat16>,
+        bool> = true>
 T min_override(T a, T b) {
   const auto float_a = static_cast<float>(a);
   if (std::isnan(float_a)) {
@@ -116,8 +118,10 @@ T min_override(T a, T b) {
 
 template <
     typename T,
-    typename std::enable_if<std::is_same<T, exec_aten::Half>::value, bool>::
-        type = true>
+    typename std::enable_if_t<
+        std::is_same_v<T, exec_aten::Half> ||
+            std::is_same_v<T, exec_aten::BFloat16>,
+        bool> = true>
 T max_override(T a, T b) {
   const auto float_a = static_cast<float>(a);
   if (std::isnan(float_a)) {

kernels/test/op_hardtanh_test.cpp

@@ -30,15 +30,31 @@ class OpHardTanhTest : public OperatorTest {
     return torch::executor::aten::hardtanh_outf(
         context_, self, min_val, max_val, out);
   }
-};
 
-TEST_F(OpHardTanhTest, SanityCheck) {
-  TensorFactory<ScalarType::Float> tf;
-  Tensor in = tf.ones({2, 2});
-  Tensor out = tf.zeros({2, 2});
+  template <typename CTYPE, ScalarType DTYPE>
+  void test_dtype() {
+    TensorFactory<DTYPE> tf;
+    CTYPE lowest_test_element;
+    CTYPE lower_bound;
+    if constexpr (std::numeric_limits<CTYPE>::is_signed) {
+      lowest_test_element = -3;
+      lower_bound = -2;
+    } else {
+      lowest_test_element = 0;
+      lower_bound = 0;
+    }
+    Tensor in = tf.make({2, 2}, {lowest_test_element, 0, 1, 100});
+    Tensor out = tf.zeros({2, 2});
+
+    Tensor ret = op_hardtanh_out(in, lower_bound, 2, out);
 
-  Tensor ret = op_hardtanh_out(in, -2, 2, out);
+    EXPECT_TENSOR_EQ(out, ret);
+    EXPECT_TENSOR_EQ(out, tf.make({2, 2}, {lower_bound, 0, 1, 2}));
+  }
+};
 
-  EXPECT_TENSOR_EQ(out, ret);
-  EXPECT_TENSOR_EQ(out, tf.ones({2, 2}));
+TEST_F(OpHardTanhTest, SanityCheck) {
+#define TEST_ENTRY(ctype, dtype) test_dtype<ctype, ScalarType::dtype>();
+  ET_FORALL_REALHBF16_TYPES(TEST_ENTRY);
+#undef TEST_ENTRY
 }