[libcxx-commits] [PATCH] D122397: [libc++] Use __builtin_expect in _LIBCPP_ASSERT

[Louis Dionne via Phabricator via libcxx-commits]

ldionne created this revision.
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Since we expect the condition to be true most of the time, we might
as well tell the compiler.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D122397

Files:
  libcxx/include/__assert


Index: libcxx/include/__assert
===================================================================
--- libcxx/include/__assert
+++ libcxx/include/__assert
@@ -34,7 +34,10 @@
 #endif
 
 #if _LIBCPP_ENABLE_ASSERTIONS
-# define _LIBCPP_ASSERT(expression, message) ((expression) ? (void)0 : ::std::__libcpp_assertion_handler(__FILE__, __LINE__, #expression, message))
+# define _LIBCPP_ASSERT(expression, message)                                        \
+    (__builtin_expect(static_cast<bool>(expression), 1) ?                           \
+      (void)0 :                                                                     \
+      ::std::__libcpp_assertion_handler(__FILE__, __LINE__, #expression, message))
 #else
 # define _LIBCPP_ASSERT(x, m) ((void)0)
 #endif


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