Re: [tip:x86/mm] x86, mm: Redesign get_user with a__builtin_choose_expr hack

From: Linus Torvalds
Date: Tue Feb 12 2013 - 18:49:33 EST

On Tue, Feb 12, 2013 at 3:19 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> Yes, but there doesn't seem to be any other way to do this. gcc won't
> even allow "=cd" even if we know the variable is 64 bits, even though
> "=A" is documented to be equivalent to "=da".

No, "=da" means value "in edx _or_ %eax". Not the same as "A".

But you're right, there's nothing similar for %ebx:%ecx. I thought
there was. I was really sure we did something special for 64-bit adc

> Let me know what you think.

I guess we don't have any choice. And the other cleanups certainly look good.

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