Re: [PATCH] powerpc: Optimise the 64bit optimised __clear_user

On 06/06/2012 10:04 PM, Paul Mackerras wrote:

On Wed, Jun 06, 2012 at 06:40:54PM +0200, Segher Boessenkool wrote:

quoted

quoted

+err1;	dcbz	r0,r3

There is no such instruction, you probably meant "dcbz 0,r3"?

There certainly is such an instruction, though it doesn't do exactly
what a naive reader might expect.  Using 0 rather than r0 or %r0
improves readability but makes no difference to the assembler or the
cpu.

The assembler can't tell that you used r0 rather than 0, because that's
handled by the preprocessor, but it seems like a bug (or at least lax
error checking) that it accepts %r0 there, and that objdump decodes it
as "dcbz r0,r3" rather than "dcbz 0,r3".

It's also odd that objdump produces output containing "r3" (not %r3)
when the assembler won't directly accept it.

-Scott