When LTO was introduced, on macOS it needed darwin9 to work. Over time, most tests for “*-apple-darwin9” in the toplevel configure were changed to also include later darwin versions: *-darwin[[912]]* However, the check for LTO was not updated. As far as I know, this is merely an oversight: LTO works fine on Darwin, and most vendors (homebrew, macports, etc.) have been shipping with --enable-lto for years.
The attached patch makes it build LTO by default on darwin >= 9. I realize it’s late but I hope the very restricted nature (and ultra-low risk) of the patch make it a candidate for inclusion in trunk nonetheless. Bootstrapped and regtested on x86_64-apple-darwin16. OK to commit? FX
lto_darwin.ChangeLog
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lto_darwin.diff
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