I've been looking how to make the precompiled header mechanism allow me to use the ARC -misize option (which outputs additional information about gcc's idea of instruction addresses for the purpose of branch shortening, to help debugging the latter) in a compilation involving precompiled headers. I can't use TARGET_CHECK_PCH_TARGET_FLAGS for that purpose because -misize uses its own variable (to save on target_flags bits). If I wanted to use the TARGET_PCH_VALID_P hook, I'd have to duplicate lots of code from default_pch_valid_p, which is intricately tied with the pch implementation, and also 'knows' that non-target flags never affect pch. Moreover, having this extra information encoded in a separate function, instead of at the specific option(s) in config/<target>/<target>.opt is rather messy.
Therefore, I propose to add a new option property to mark an option that should be ignored for the purpose of checking pch validity. The attached patch implements this as PchIgnore. bootstrapped on i686-pc-linux.gnu. OK to apply?
pch-ignore-patch
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