Messages in this thread | | | From | Marcin Dalecki <> | Subject | Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/ | Date | Sun, 27 Mar 2005 05:18:04 +0200 |
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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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