[flang-commits] [clang] [flang] [Flang][Driver] Deprecate Ofast (PR #101701)

[Kiran Chandramohan via flang-commits]

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@@ -933,10 +933,12 @@ def O : Joined<["-"], "O">, Group<O_Group>,
 def O_flag : Flag<["-"], "O">, Visibility<[ClangOption, CC1Option, FC1Option]>,
   Alias<O>, AliasArgs<["1"]>;
 def Ofast : Joined<["-"], "Ofast">, Group<O_Group>,
-  Visibility<[ClangOption, CC1Option, FlangOption]>,
-  HelpTextForVariants<[ClangOption, CC1Option],
-                      "Deprecated; use '-O3 -ffast-math' for the same behavior,"
-                      " or '-O3' to enable only conforming optimizations">;
+  Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
+  HelpTextForVariants<[FlangOption, FC1Option],
+    "Deprecated; use '-O3 -ffast-math -fstack-arrays' for the same behavior,"
+    " or '-O3 -fstack-arrays' to enable only conforming optimizations">,
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kiranchandramohan wrote:

This is currently mimicking gfortran (https://gcc.gnu.org/onlinedocs/gfortran/Code-Gen-Options.html), which runs it at Ofast.

We have not seen much benefits because Flang mostly allocates on the stack. @tblah is that right?

https://github.com/llvm/llvm-project/pull/101701