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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/103882] Register corruption in ASM only functions when
 optization is -O2/-Os/-O3
Date: Sun, 02 Jan 2022 13:27:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103882

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|WONTFIX                     |INVALID

--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
There is no special case for inline asm as the whole body of a function (ex=
cept
that __attribute__((naked)) functions need to contain just that), it acts l=
ike
any other inline asm.  And like for any other inline asm, the user needs to
tell the compiler what side-effects it has.
You can define the whole function in top-level inline asm or in *.s/*.S fil=
e,
then the ABI applies for it.
Or just use the syscall function, see syscall(2) man page.
A hack that you want to propose (forcing noipa on functions that use inline
asm) certainly won't be accepted, that would penalize millions of correctly
written inline asm statements in real-world code.  Even if it is limited on=
ly
to functions that contain just a single inline asm statement and nothing el=
se.=20
Because even those are often desirable for inlining etc.
IPA RA is a very useful optimization, not something terrible.
And I've only spent last 23+ years working on GCC, so yes, I can't know the
codebase enough.=