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GNU_PROPERTY_X86_* questions
- From: Jan Beulich <jbeulich at suse dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: "binutils at sourceware dot org" <binutils at sourceware dot org>
- Date: Thu, 10 Oct 2019 15:33:04 +0200
- Subject: GNU_PROPERTY_X86_* questions
H.J.,
I think I'm seeing a number of issues with the handling of these
properties in gas, but without the original commit referencing a
specification I can't really determine if some or all of these
are actually "working as designed".
Some of the points are:
- What is the actual meaning of a set bit? I.e. should e.g. -O
converting between ISAs actually be reflected in the produced
note?
- What is the rule of ISAs to get (or not get) a flag defined?
E.g. why are there AVX, AVX2, and FMA flags, but no XOP nor
FMA4 ones?
- What is the rule of register sets getting feature flags
defined? E.g. why are there XMM etc flags but there's no mask
register one?
- What are the rules for the feature flags actually getting set?
I find it puzzling that there are straight use
i.has_reg{x,y,z}mm flags (which could be easily done away
with), but for MMX quite a bit of extra logic is involved.
Thanks, Jan