Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/

[Marcin Dalecki]

On 2005-03-27, at 04:00, Horst von Brand wrote:
> > Needless to say that there are enough architectures out there, which
> > don't even have something like an explicit call as separate assembler
> > instruction...
>
> The mechanism exists somehow.

Most RISC architectures are claiming a huge register set advantage over 
IA32.
However in reality it's normal that:

1. Some of the register take roles as declared by the ABI. One is stack 
one
is basis pointer and so no.
2. Only a subset of register is declared to be guaranteed to be 
preserved by
system calls.

Thus the mechanisms are simple calling conventions.

Compilers can frequently see what a subroutine does and can flatten out 
the cost
of function calls to something very much resembling just two jumps 
instead of
a single jump around a condition.

On the other hand most modern IA32 implementation (since cyrix 486) are 
very
efficient at mapping stack operations to a special cache between the 
CPU and
L1 cache. I could even imagine them to be more efficient then plain 
jumps, which
simply don't carry the same information for cache prefetch and branch 
predition.

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