On Tue, Oct 06, 2015 at 12:21:05PM +0100, Dave Gordon wrote:
> ... although I still think my version is (slightly) easier to read.
> Or it could be improved even more by moving the increment of 'iter'
> to the end, making it one line shorter and perhaps helping the
> compiler a little :)
>
> #define gen8_for_each_pml4e(pdp, pml4, start, length, temp, iter) \
> for (iter = gen8_pml4e_index(start); \
> iter < GEN8_PML4ES_PER_PML4 && \
> (pdp = (pml4)->pdps[iter], length > 0); \
> temp = ALIGN(start+1, 1ULL << GEN8_PML4E_SHIFT) - start, \
> temp = min(temp, length), \
> start += temp, length -= temp, ++iter)
Shorter, yes, but we may as well take advantage of not using [iter] if
length == 0, so meh.
> Or, noting that 'temp' is never used in the generated loop bodies,
> we could eliminate the parameter and make it local to the loop
> header :)
>
> #define gen8_for_each_pml4e(pdp, pml4, start, length, iter) \
> for (iter = gen8_pml4e_index(start); \
> iter < GEN8_PML4ES_PER_PML4 && \
> (pdp = (pml4)->pdps[iter], length > 0); \
> ({ u64 temp = ALIGN(start+1, 1ULL << GEN8_PML4E_SHIFT); \
> temp = min(temp - start, length); \
> start += temp, length -= temp; }), \
> ++iter)
Removing extraneous parameters from macros is differently a usability win.
Care to spin a real patch so we can see how it looks in practice?
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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