[libcxx-commits] [libcxx] 7f2e9b1 - Revert "[libc++] Mark __{emplace, push}_back_slow_path as noinline (#94379)"

[Aiden Grossman via libcxx-commits]

Author: Aiden Grossman
Date: 2025-09-12T21:24:15Z
New Revision: 7f2e9b17098f42c85ef469b029bb84ef4eea189c

URL: https://github.com/llvm/llvm-project/commit/7f2e9b17098f42c85ef469b029bb84ef4eea189c
DIFF: https://github.com/llvm/llvm-project/commit/7f2e9b17098f42c85ef469b029bb84ef4eea189c.diff

LOG: Revert "[libc++] Mark __{emplace,push}_back_slow_path as noinline (#94379)"

This reverts commit 1bafd020c7c80be476f211bc239ce43424f7e0ce.

This breaks the LLDB data formatters which means these failures show up
on every premerge run. Reverting for now until fixing the LLDB
formatters can be coordinated with a relanding.

Added: 
    

Modified: 
    libcxx/include/__vector/vector.h

Removed: 
    


################################################################################
diff  --git a/libcxx/include/__vector/vector.h b/libcxx/include/__vector/vector.h
index 27e681aeef22a..5e6572b1a82c4 100644
--- a/libcxx/include/__vector/vector.h
+++ b/libcxx/include/__vector/vector.h
@@ -1161,24 +1161,6 @@ vector<_Tp, _Allocator>::__emplace_back_slow_path(_Args&&... __args) {
   return this->__end_;
 }
 
-// This makes the compiler inline `__else()` if `__cond` is known to be false. Currently LLVM doesn't do that without
-// the `__builtin_constant_p`, since it considers `__else` unlikely even through it's known to be run.
-// See https://llvm.org/PR154292
-template <class _If, class _Else>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void __if_likely_else(bool __cond, _If __if, _Else __else) {
-  if (__builtin_constant_p(__cond)) {
-    if (__cond)
-      __if();
-    else
-      __else();
-  } else {
-    if (__cond) [[__likely__]]
-      __if();
-    else
-      __else();
-  }
-}
-
 template <class _Tp, class _Allocator>
 template <class... _Args>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 inline
@@ -1189,14 +1171,12 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 inline
 #endif
     vector<_Tp, _Allocator>::emplace_back(_Args&&... __args) {
   pointer __end = this->__end_;
-  std::__if_likely_else(
-      __end < this->__cap_,
-      [&] {
-        __emplace_back_assume_capacity(std::forward<_Args>(__args)...);
-        ++__end;
-      },
-      [&] { __end = __emplace_back_slow_path(std::forward<_Args>(__args)...); });
-
+  if (__end < this->__cap_) {
+    __emplace_back_assume_capacity(std::forward<_Args>(__args)...);
+    ++__end;
+  } else {
+    __end = __emplace_back_slow_path(std::forward<_Args>(__args)...);
+  }
   this->__end_ = __end;
 #if _LIBCPP_STD_VER >= 17
   return *(__end - 1);