Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX

Andi Kleen
2008-03-10T21:50:10Z

> Please also note that these are not clobbers in the strict inline asm
> syntax, but rather dummy output values that correspond to actual

Outputs/Inputs are as bad as clobbers in triggering gcc reload ICEs.

> input parameters. I'd consider this a serious compiler flaw, if not
> bug, if these would not work. But let's not get into GCC vs.

It is, and it's (mostly) fixed in newer versions, but we're stuck with
supporting the older compiler versions unfortunately.

> > For asms with so many clobbers explicit push/pop is usually safer.
>
> Yes, but it is unneccessary overhead as the compiler can (should!)
> find more elegant ways to get those registers back if needed.

This code is not performance critical at all. Safer beats faster
any time in such cases.

-Andi