[llvm-branch-commits] [clang] release/19.x: Ofast deprecation clarifications (#101005) (PR #101663)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport 48d4d4b641702bf6db03a1bac73b7e13dea28349

Requested by: @<!-- -->AaronBallman

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Full diff: https://github.com/llvm/llvm-project/pull/101663.diff


1 Files Affected:

- (modified) clang/docs/CommandGuide/clang.rst (+6-2) 


``````````diff
diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index 663aca1f6ddcb..a0c2594d06c61 100644
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -429,8 +429,12 @@ Code Generation Options
 
     :option:`-Ofast` Enables all the optimizations from :option:`-O3` along
     with other aggressive optimizations that may violate strict compliance with
-    language standards. This is deprecated in favor of :option:`-O3`
-    in combination with :option:`-ffast-math`.
+    language standards. This is deprecated in Clang 19 and a warning is emitted
+    that :option:`-O3` in combination with :option:`-ffast-math` should be used
+    instead if the request for non-standard math behavior is intended. There
+    is no timeline yet for removal; the aim is to discourage use of
+    :option:`-Ofast` due to the surprising behavior of an optimization flag
+    changing the observable behavior of correct code.
 
     :option:`-Os` Like :option:`-O2` with extra optimizations to reduce code
     size.

``````````

</details>


https://github.com/llvm/llvm-project/pull/101663