Remove custom microsoft mangling logic. I believe it's no longer needed now that we don't have an iostream ODR violation.

Author: matts1

libcxx/src/iostream.cpp

@@ -33,31 +33,13 @@ union stream_data {
   }
 };
 
-#define CHAR_MANGLING_char "D"
-#define CHAR_MANGLING_wchar_t "_W"
-#define CHAR_MANGLING(CharT) CHAR_MANGLING_##CharT
-
-#ifdef _LIBCPP_COMPILER_CLANG_BASED
-#  define STRING_DATA_CONSTINIT constinit
-#else
-#  define STRING_DATA_CONSTINIT
-#endif
-
-#ifdef _LIBCPP_ABI_MICROSOFT
-#  define STREAM(StreamT, BufferT, CharT, var)                                                                         \
-    STRING_DATA_CONSTINIT stream_data<StreamT<CharT>, BufferT<CharT>> var __asm__(                                     \
-        "?" #var "@" ABI_NAMESPACE_STR "@std@@3V?$" #StreamT                                                           \
-        "@" CHAR_MANGLING(CharT) "U?$char_traits@" CHAR_MANGLING(CharT) "@" ABI_NAMESPACE_STR "@std@@@12@A")
-#else
-
 // To avoid ODR violations without breaking the ABI, we need to define it as a StreamT<CharT>.
 // However, since initialization order of statics is arbitrary, we could run DoIOSInit first and then
 // construct the stream for a second time, overwriting the data in it.
 // To avoid this, we call a constructor overload that specifically avoids initializing any members.
-#  define STREAM(StreamT, BufferT, CharT, var)                                                                         \
-    StreamT<CharT> var{std::__uninitialized_ios_tag{}};                                                                \
-    stream_data<BufferT<CharT>, StreamT<CharT>, var> sd_##var;
-#endif
+#define STREAM(StreamT, BufferT, CharT, var)                                                                           \
+  StreamT<CharT> var{std::__uninitialized_ios_tag{}};                                                                  \
+  stream_data<BufferT<CharT>, StreamT<CharT>, var> sd_##var;
 
 _LIBCPP_EXPORTED_FROM_ABI STREAM(basic_istream, __stdinbuf, char, cin)
 _LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, char, cout)