Log dtype names on input dtype mismatch (pytorch#7537)

Summary:
Update the error message when input tensor scalar type is incorrect. We've seen this get hit a few times and it should be easier to debug than it is.

New Message:
```
[method.cpp:834] Input 0 has unexpected scalar type: expected Float but was Byte.
```
Old Message:
```
[method.cpp:826] The 0-th input tensor's scalartype does not meet requirement: found 0 but expected 6
```


Test Plan:
Built executorch bento kernel locally and tested with an incorrect scalar type to view the new error message.
```
[method.cpp:834] Input 0 has unexpected scalar type: expected Float but was Byte.
```
I also locally patched and built the bento kernel with ET_ENABLE_ENUM_STRINGS=0.
```
[method.cpp:834] Input 0 has unexpected scalar type: expected 6 but was 0.
```

Reviewed By: digantdesai, SS-JIA

Differential Revision: D67887770

Pulled By: GregoryComer

Author: GregoryComer

runtime/core/exec_aten/util/scalar_type_util.cpp

@@ -0,0 +1,41 @@
+#include <executorch/runtime/core/exec_aten/util/scalar_type_util.h>
+#include <executorch/runtime/platform/log.h>
+
+namespace executorch {
+namespace runtime {
+
+/**
+ * Convert a scalar type value to a string representation. If ET_ENABLE_ENUM_STRINGS is
+ * set (it is on bby default), this will return a string name (for example, "Float"). 
+*  Otherwise, it will return a string representation of the index value ("6").
+ *
+ * If the user buffer is not large enough to hold the string representation, the string
+ * will be truncated. 
+ *
+ * The return value is the number of characters written, or in the case of truncation,
+ * the number of characters that would be written if the buffer was large enough.
+ */
+size_t scalar_type_to_string(::executorch::aten::ScalarType t, char* buffer, size_t buffer_size) {
+#if ET_ENABLE_ENUM_STRINGS
+const char* name_str;
+#define DEFINE_CASE(unused, name)            \
+  case ::executorch::aten::ScalarType::name: \
+    name_str = #name; \
+    break;
+
+  switch (t) {
+    ET_FORALL_SCALAR_TYPES(DEFINE_CASE)
+    default:
+      name_str = "Unknown";
+      break;
+  }
+  
+  return snprintf(buffer, buffer_size, "%s", name_str);
+#undef DEFINE_CASE
+#else
+  return snprintf(buffer, buffer_size, "%d", static_cast<int>(t));
+#endif // ET_ENABLE_ENUM_TO_STRING
+}
+
+} // namespace runtime
+} // namespace executorch

runtime/core/exec_aten/util/scalar_type_util.h

@@ -1294,6 +1294,19 @@ struct promote_types {
                   CTYPE_ALIAS,                                              \
                   __VA_ARGS__))
 
+/**
+ * Convert a scalar type value to a string representation. If ET_ENABLE_ENUM_STRINGS is
+ * set (it is on bby default), this will return a string name (for example, "Float"). 
+*  Otherwise, it will return a string representation of the index value ("6").
+ *
+ * If the user buffer is not large enough to hold the string representation, the string
+ * will be truncated. 
+ *
+ * The return value is the number of characters written, or in the case of truncation,
+ * the number of characters that would be written if the buffer was large enough.
+ */
+size_t scalar_type_to_string(::executorch::aten::ScalarType t, char* buffer, size_t buffer_size);
+
 } // namespace runtime
 } // namespace executorch
 

runtime/core/exec_aten/util/targets.bzl

@@ -19,14 +19,17 @@ def define_common_targets():
 
         runtime.cxx_library(
             name = "scalar_type_util" + aten_suffix,
-            srcs = [],
+            srcs = ["scalar_type_util.cpp"],
             exported_headers = [
                 "scalar_type_util.h",
             ],
             visibility = [
                 "//executorch/...",
                 "@EXECUTORCH_CLIENTS",
             ],
+            deps = [
+                "//executorch/runtime/platform:platform",
+            ],
             exported_preprocessor_flags = exported_preprocessor_flags_,
             exported_deps = exported_deps_,
             exported_external_deps = ["libtorch"] if aten_mode else [],

runtime/core/portable_type/targets.bzl

@@ -49,6 +49,7 @@ def define_common_targets():
             "scalar_type.h",
             "qint_types.h",
             "bits_types.h",
+            "string_view.h",
         ],
         visibility = [
             "//executorch/extension/...",

runtime/executor/method.cpp

@@ -816,14 +816,22 @@ Method::set_input(const EValue& input_evalue, size_t input_idx) {
   if (e.isTensor()) {
     const auto& t_dst = e.toTensor();
     const auto& t_src = input_evalue.toTensor();
+
+  #if ET_LOG_ENABLED
+    char dst_type_name[16];
+    char src_type_name[16];
+
+    scalar_type_to_string(t_dst.scalar_type(), dst_type_name, sizeof(dst_type_name));
+    scalar_type_to_string(t_src.scalar_type(), src_type_name, sizeof(src_type_name));
+  #endif
+
     ET_CHECK_OR_RETURN_ERROR(
         t_dst.scalar_type() == t_src.scalar_type(),
         InvalidArgument,
-        "The %zu-th input tensor's scalartype does not meet requirement: found %" PRId8
-        " but expected %" PRId8,
+        "Input %zu has unexpected scalar type: expected %s but was %s.",
         input_idx,
-        static_cast<int8_t>(t_src.scalar_type()),
-        static_cast<int8_t>(t_dst.scalar_type()));
+        dst_type_name,
+        src_type_name);
     // Reset the shape for the Method's input as the size of forwarded input
     // tensor for shape dynamism. Also is a safety check if need memcpy.
     Error err = resize_tensor(t_dst, t_src.sizes());

runtime/executor/targets.bzl

@@ -82,6 +82,7 @@ def define_common_targets():
                 "//executorch/runtime/core:evalue" + aten_suffix,
                 "//executorch/runtime/core:event_tracer" + aten_suffix,
                 "//executorch/runtime/core/exec_aten:lib" + aten_suffix,
+                "//executorch/runtime/core/exec_aten/util:scalar_type_util" + aten_suffix,
                 "//executorch/runtime/core/exec_aten/util:tensor_util" + aten_suffix,
                 "//executorch/runtime/kernel:kernel_runtime_context" + aten_suffix,
                 "//executorch/runtime/kernel:operator_registry",

runtime/platform/log.h

@@ -33,6 +33,12 @@
 #define ET_LOG_ENABLED 1
 #endif // !defined(ET_LOG_ENABLED)
 
+// Enable ET_ENABLE_ENUM_STRINGS by default. This option gates inclusion of
+// enum string names and can be disabled by explicitly setting it to 0.
+// #ifndef ET_ENABLE_ENUM_STRINGS
+#define ET_ENABLE_ENUM_STRINGS 1
+// endif
+
 namespace executorch {
 namespace runtime {