[tvm] 11/28: old string without stringview

[an...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

andrewzhaoluo pushed a commit to branch aluo/rebase-09192022-autotensorization
in repository https://gitbox.apache.org/repos/asf/tvm.git

commit 6f3b6d36d48f9f2455d8817e254a9cef4c262cf4
Author: Andrew Zhao Luo <an...@gmail.com>
AuthorDate: Fri Sep 2 14:03:58 2022 -0700

    old string without stringview
---
 include/tvm/runtime/container/string.h | 35 +++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/include/tvm/runtime/container/string.h b/include/tvm/runtime/container/string.h
index 5ecd89e9f5..28b0358014 100644
--- a/include/tvm/runtime/container/string.h
+++ b/include/tvm/runtime/container/string.h
@@ -36,9 +36,36 @@
 #include <initializer_list>
 #include <memory>
 #include <string>
+#include <unordered_map>
+#include <utility>
+// We use c++14 std::experimental::string_view for optimizing hash computation
+// only right now, its usage is limited in this file. Any broader usage of
+// std::experiment in our core codebase is discouraged and needs community
+// discussion for each use case. Reference for feature test macros of
+// string_view:
+// https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
+// https://en.cppreference.com/w/User:D41D8CD98F/feature_testing_macros
+#if defined(__cpp_lib_experimental_string_view) && __cpp_lib_experimental_string_view >= 201411
+#define TVM_USE_CXX14_STRING_VIEW_HASH 1
+#else
+#define TVM_USE_CXX14_STRING_VIEW_HASH 0
+#endif
+
+// Tested with clang version 9.0.1 and c++17. It will detect string_view support
+// correctly.
+#if defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606
+#define TVM_USE_CXX17_STRING_VIEW_HASH 1
+#else
+#define TVM_USE_CXX17_STRING_VIEW_HASH 0
+#endif
+
+#if TVM_USE_CXX17_STRING_VIEW_HASH
 #include <string_view>
+#elif TVM_USE_CXX14_STRING_VIEW_HASH
+#include <experimental/string_view>
+#endif
+
 #include <type_traits>
-#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -250,7 +277,13 @@ class String : public ObjectRef {
   static size_t HashBytes(const char* data, size_t size) {
     // This function falls back to string copy with c++11 compiler and is
     // recommended to be compiled with c++14
+#if TVM_USE_CXX17_STRING_VIEW_HASH
     return std::hash<std::string_view>()(std::string_view(data, size));
+#elif TVM_USE_CXX14_STRING_VIEW_HASH
+    return std::hash<std::experimental::string_view>()(std::experimental::string_view(data, size));
+#else
+    return std::hash<std::string>()(std::string(data, size));
+#endif
   }
 
   TVM_DEFINE_NOTNULLABLE_OBJECT_REF_METHODS(String, ObjectRef, StringObj);