Gerd Hoffmann <kra...@redhat.com> writes:
> From: Radim Krčmář <rkrc...@redhat.com>
>
> We already have pow2floor, mirror it and use instead of a function with
> similar results (same in used domain), to clarify our intent.
>
> Signed-off-by: Radim Krčmář <rkrc...@redhat.com>
> Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
[...]
> diff --git a/include/qemu-common.h b/include/qemu-common.h
> index 644b46d..1b5cffb 100644
> --- a/include/qemu-common.h
> +++ b/include/qemu-common.h
> @@ -418,6 +418,9 @@ static inline bool is_power_of_2(uint64_t value)
> /* round down to the nearest power of 2*/
> int64_t pow2floor(int64_t value);
>
> +/* round up to the nearest power of 2 (0 if overflow) */
> +uint64_t pow2ceil(uint64_t value);
> +
> #include "qemu/module.h"
>
> /*
> diff --git a/util/cutils.c b/util/cutils.c
> index dbe7412..c2250d1 100644
> --- a/util/cutils.c
> +++ b/util/cutils.c
> @@ -483,6 +483,20 @@ int64_t pow2floor(int64_t value)
> return value;
> }
>
> +/* round up to the nearest power of 2 (0 if overflow) */
Callers need to check for overflow, but that's the callers' problem.
> +uint64_t pow2ceil(uint64_t value)
> +{
> + uint8_t nlz = clz64(value);
You convert the value of clz64() from int to uint8_t only to promote it
right back to int in every single use. Please don't muddy the waters
that way.
> +
> + if (is_power_of_2(value)) {
> + return value;
> + }
> + if (!nlz) {
> + return 0;
> + }
> + return 1ULL << (64 - nlz);
> +}
> +
> /*
> * Implementation of ULEB128 (http://en.wikipedia.org/wiki/LEB128)
> * Input is limited to 14-bit numbers
Doesn't really mirror pow2floor() in master, because that one uses
int64_t. Fine with me, because my "[PATCH 0/2] Proactive pow2floor()
fix, and dead code removal" changes pow2floor() to uint64_t.
Unfortunately, the two patches conflict.
This patch's implementation of pow2ceil() is needlessly complicated,
just like pow2floor() in master. Simpler:
uint64_t pow2ceil2(uint64_t value)
{
int n = clz64(value - 1);
return n ? 1ull << (64 - n) : 0;
}
I can rebase my patch on top of this one, and clean things up to my
taste.
