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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/103095] Option to force no overalignment
Date: Sun, 07 Nov 2021 00:05:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103095

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
   AMD x86-64 psABI says that variables with array type larger than 15 bytes
   must be aligned to 16 byte boundaries.


There is already an option:
https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/x86-Options.html#index-malign=
-data-1
-malign-data=3Dtype
Control how GCC aligns variables. Supported values for type are =E2=80=98co=
mpat=E2=80=99 uses
increased alignment value compatible uses GCC 4.8 and earlier, =E2=80=98abi=
=E2=80=99 uses
alignment value as specified by the psABI, and =E2=80=98cacheline=E2=80=99 =
uses increased
alignment value to match the cache line size. =E2=80=98compat=E2=80=99 is t=
he default.


You just need to supply -mabi-data=3Dabi in this case if you want to disabl=
e over
aligning of things.

Other than that there is nothing to be done in GCC; it is up to the linker =
and
assembler to do the layout really.

The option was added in GCC 5 by r5-5887.=