Messages in this thread | | | Date | Fri, 17 Aug 2007 21:13:35 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures |
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On Sat, 18 Aug 2007, Satyam Sharma wrote: > > No code does (or would do, or should do): > > x.counter++; > > on an "atomic_t x;" anyway.
That's just an example of a general problem.
No, you don't use "x.counter++". But you *do* use
if (atomic_read(&x) <= 1)
and loading into a register is stupid and pointless, when you could just do it as a regular memory-operand to the cmp instruction.
And as far as the compiler is concerned, the problem is the 100% same: combining operations with the volatile memop.
The fact is, a compiler that thinks that
movl mem,reg cmpl $val,reg
is any better than
cmpl $val,mem
is just not a very good compiler. But when talking about "volatile", that's exactly what ytou always get (and always have gotten - this is not a regression, and I doubt gcc is alone in this).
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