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SubjectRe: [PATCH] 2.1.131: i386 tweak to switch_to()
Andrea Arcangeli <> said:
> On Sat, 12 Dec 1998, Jamie Lokier wrote:
> >+ :"ebx", "ecx", "esi", "edi", "cc", "memory"); \
> ^^^^^^^^^^^^^^
> What is "cc" and why we need to declare "memory" clobbered after using
> __switch_to()?

"cc" is condition flags; "memory" is clobbered each time you write to
something that is not in the arguments. Clobbering "memory" is used to
singal gcc that it can't assume that memory is unchanged (i.e., reuse a
value in memory that just happens to be in a register), and also has the
side effect that it acts as a barrier: No reordering of instructions will
move stuff over the asm() because of the above.
Dr. Horst H. von Brand
Departamento de Informatica Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria +56 32 654239
Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513

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