On Mon, 28/03/2011 at 07:08 +0200, Ingo Molnar wrote:
> Have you looked at the disassembly, why does the size increase? I'd expect such
> a straight assembly optimization to result in smaller code: in the non-constant
> case it should be the same size as before, in the constant case it should be
> smaller, because BSR should be smaller than an open-coded search loop, right?
Here is disassembly of patched get_order() with "inline" from
"kernel/kexec.c":
a6c: 48 8b 5d c8 mov -0x38(%rbp),%rbx
a70: e8 0b fd ff ff callq 780 <get_order.clone.7>
0000000000000780 <get_order.clone.7>:
780: 55 push %rbp
781: b8 01 00 00 00 mov $0x1,%eax
786: 48 89 e5 mov %rsp,%rbp
789: c9 leaveq
78a: c3 retq
My version of gcc is gcc (Debian 4.5.2-4) 4.5.2, probably I should
upgrade my gcc version for better inline expansions.
--
Thanks,
Maksym Planeta
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