Set optsize and minsize fun attributes for the -Os and -Oz optimization modes#16983
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ysbaddaden wants to merge 2 commits into
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Set optsize and minsize fun attributes for the -Os and -Oz optimization modes#16983ysbaddaden wants to merge 2 commits into
optsize and minsize fun attributes for the -Os and -Oz optimization modes#16983ysbaddaden wants to merge 2 commits into
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…on modes LLVM 23 removed the PassBuilder support for default<Os> and default<Oz> that was introduced in LLVM 17. We now use the default<O2> optimization level, and set the optsize (Os) or minsize (Oz) function attribute to every functions, which has the same behavior. Bonus: this enables support for -Oz and -Oz for LLVM 13-16.
ysbaddaden
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optsize and minsize fun attributes for the -Os and -Oz optimization modes
Sija
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May 19, 2026
straight-shoota
approved these changes
May 20, 2026
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LLVM 23 removes the
PassBuildersupport fordefault<Os>anddefault<Oz>that was introduced in LLVM 17.Instead, we shall use the
default<O2>optimization level, and set theoptsize(-Os) orminsize(-Oz) function attribute to every functions, which has the same behavior. This in turn enables support for-Ozand-Ozfor LLVM 13 to 16.I manually tested against different LLVM versions (15, 18, 21 and 23):
-Osis smaller than any-O0to-O3level, and-Ozis even smaller.closes #16895
related to #14463