On 22/03/17 06:27, Zhen Lei wrote:
> Below judgement can only be satisfied at the last time, which produced 2N
> judgements(suppose N times failed, 0 or 1 time successed) in vain.
>
> if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
> return iova;
> }
For me, GCC (6.2.1 AArch64) seems to do a pretty good job of this
function already, so this change only saves two instructions in total
(pfn is compared against pfn_lo only once instead of twice), which I
wouldn't expect to see a noticeable performance effect from.
Given the improvement in readability, though, I don't even care about
any codegen differences :)
Reviewed-by: Robin Murphy <robin.mur...@arm.com>
> Signed-off-by: Zhen Lei <thunder.leiz...@huawei.com>
> ---
> drivers/iommu/iova.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 8ba8b496..1c49969 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -312,15 +312,12 @@ private_find_iova(struct iova_domain *iovad, unsigned
> long pfn)
> while (node) {
> struct iova *iova = rb_entry(node, struct iova, node);
>
> - /* If pfn falls within iova's range, return iova */
> - if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
> - return iova;
> - }
> -
> if (pfn < iova->pfn_lo)
> node = node->rb_left;
> - else if (pfn > iova->pfn_lo)
> + else if (pfn > iova->pfn_hi)
> node = node->rb_right;
> + else
> + return iova; /* pfn falls within iova's range */
> }
>
> return NULL;
>
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