On Wed, Apr 21, 2021 at 10:43 AM David Laight [off-list ref] wrote:

From: Arnd Bergmann Sent: 20 April 2021 22:20

quoted

On Tue, Apr 20, 2021 at 11:14 PM Vineet Gupta [off-list ref] wrote:

quoted

On 4/20/21 12:07 AM, Arnd Bergmann wrote:

quoted

quoted

which means that half the 32-bit architectures do this. This may
cause more problems when arc and/or microblaze want to support
64-bit kernels and compat mode in the future on their latest hardware,
as that means duplicating the x86 specific hacks we have for compat.

What is alignof(u64) on 64-bit arc?

$ echo 'int a = __alignof__(long long);' | arc64-linux-gnu-gcc -xc -
-Wall -S -o - | grep -A1 a: | tail -n 1 | cut -f 3
8

Ok, good.

That test doesn't prove anything.
Try running on x86:
$ echo 'int a = __alignof__(long long);' | gcc -xc - -Wall -S -o - -m32
a:
        .long   8

Right, I had wondered about that one after I sent the email.

Using '__alignof__(struct {long long x;})' does give the expected 4.

__alignof__() returns the preferred alignment, not the enforced
alignmnet - go figure.

I checked the others as well now, and i386 is the only one that
changed here: m68k still has '2', while arc/csky/h8300/microblaze/
nios2/or1k/sh/i386 all have '4' and the rest have '8'.

     Arnd

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