[PATCH] D13713: [libc++] Stop marking interface symbols always_inline + hidden when building for unstable ABI

[Evgeniy Stepanov via cfe-commits]

eugenis created this revision.
eugenis added reviewers: mclow.lists, EricWF.
eugenis added a subscriber: cfe-commits.
eugenis set the repository for this revision to rL LLVM.
Herald added a subscriber: aemerson.

ABI stability is not an issue when building for unstable ABI.
Other than that, always_inline is mostly harmful:
- it does not completely solve the ABI stability problem, because there is no guarantee that an always_inline function will be inlined.
- it really harms -O0 where indiscriminate inlining results in huge stack frames.
- check-libcxx becomes faster by 18% when always_inline is removed


Repository:
  rL LLVM

http://reviews.llvm.org/D13713

Files:
  include/__config

Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -31,6 +31,13 @@
 #define _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
 #endif
 
+#if defined(_LIBCPP_ABI_UNSTABLE)
+// The only purpose of the always_inline thing is ABI stability.
+// Disable it when building for unstable ABI.
+#define _LIBCPP_INLINE_VISIBILITY
+#define _LIBCPP_ALWAYS_INLINE
+#endif
+
 #define _LIBCPP_CONCAT1(_LIBCPP_X,_LIBCPP_Y) _LIBCPP_X##_LIBCPP_Y
 #define _LIBCPP_CONCAT(_LIBCPP_X,_LIBCPP_Y) _LIBCPP_CONCAT1(_LIBCPP_X,_LIBCPP_Y)
 


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