Update attributes.md

prjoseph · web-flow · commit 34ae52a8a1d8 · 2022-04-27T09:47:29.000-07:00
We had 2 feedback bugs for likely/unlikely where customers commented about block reordering optimization not happening when they specify these attributes. As per the request of one of the feedback tickets, adding a specific note about this optimization not being implemented yet in the compier. https://developercommunity.visualstudio.com/t/Gy-changes-C20-branch-hint-optimiza/10023042#T-ND10024186 https://developercommunity.visualstudio.com/t/likely--unlikely-should-avoid-c/1603545
diff --git a/docs/cpp/attributes.md b/docs/cpp/attributes.md
@@ -52,9 +52,9 @@ Attributes represent a standardized alternative to vendor-specific extensions su
 
 - `[[maybe_unused]]` **Visual Studio 2017 version 15.3 and later:** (Available with [`/std:c++17`](../build/reference/std-specify-language-standard-version.md) and later.) Specifies that a variable, function, class, typedef, non-static data member, enum, or template specialization may be intentionally unused. The compiler doesn't warn when an entity marked `[[maybe_unused]]` isn't used. An entity that's declared without the attribute can later be redeclared with the attribute and vice-versa. An entity is considered *marked* after its first declaration that's marked `[[maybe_unused]]` gets analyzed, and for the rest of the current translation unit.
 
-- `[[likely]]` **Visual Studio 2019 version 16.6 and later:** (Available with [`/std:c++20`](../build/reference/std-specify-language-standard-version.md) and later.) Specifies a hint to the compiler that the code path for the attributed label or statement is more likely to execute than alternatives. In the Microsoft compiler, the `[[likely]]` attribute marks blocks as "hot code", which increments an internal optimization score. The score is incremented more when optimizing for speed, and not as much when optimizing for size. The net score affects the likelihood of inlining, loop unrolling, and vectorizing optimizations. The effect of `[[likely]]` and `[[unlikely]]` is similar to [Profile-guided optimization](../build/profile-guided-optimizations.md), but limited in scope to the current translation unit.
+- `[[likely]]` **Visual Studio 2019 version 16.6 and later:** (Available with [`/std:c++20`](../build/reference/std-specify-language-standard-version.md) and later.) Specifies a hint to the compiler that the code path for the attributed label or statement is more likely to execute than alternatives. In the Microsoft compiler, the `[[likely]]` attribute marks blocks as "hot code", which increments an internal optimization score. The score is incremented more when optimizing for speed, and not as much when optimizing for size. The net score affects the likelihood of inlining, loop unrolling, and vectorizing optimizations. The effect of `[[likely]]` and `[[unlikely]]` is similar to [Profile-guided optimization](../build/profile-guided-optimizations.md), but limited in scope to the current translation unit. Please note that block re-ordering optimization is not yet implemented for this attribute.
 
-- `[[unlikely]]` **Visual Studio 2019 version 16.6 and later:** (Available with [`/std:c++20`](../build/reference/std-specify-language-standard-version.md) and later.) Specifies a hint to the compiler that the code path for the attributed label or statement is less likely to execute than alternatives. In the Microsoft compiler, the `[[unlikely]]` attribute marks blocks as "cold code", which decrements an internal optimization score. The score is decremented more when optimizing for size, and not as much when optimizing for speed. The net score affects the likelihood of inlining, loop unrolling, and vectorizing optimizations.
+- `[[unlikely]]` **Visual Studio 2019 version 16.6 and later:** (Available with [`/std:c++20`](../build/reference/std-specify-language-standard-version.md) and later.) Specifies a hint to the compiler that the code path for the attributed label or statement is less likely to execute than alternatives. In the Microsoft compiler, the `[[unlikely]]` attribute marks blocks as "cold code", which decrements an internal optimization score. The score is decremented more when optimizing for size, and not as much when optimizing for speed. The net score affects the likelihood of inlining, loop unrolling, and vectorizing optimizations. Please note that block re-ordering optimization is not yet implemented for this attribute.
 
 ## Microsoft-specific attributes
 
