On Wed, 2 Oct 2019, Julien Grall wrote:
> Clang is pickier than GCC for the register size in asm statement. It expects
> the register size to match the value size.
>
> The instruction clz is expecting the two operands to be the same size
> (i.e 32-bit or 64-bit). As the flsl function is dealing with 64-bit
> value, we need to make the destination variable 64-bit as well.
>
> While at it, add a newline before the return statement.
>
> Note that the return type of flsl is not updated because the result will
> always be smaller than 64 and therefore fit in 32-bit.
>
> Signed-off-by: Julien Grall <julien.gr...@arm.com>
Acked-by: Stefano Stabellini <sstabell...@kernel.org>
> ---
> Changes in v2:
> - Update the commit message to explain why the return type is
> not modified
> ---
> xen/include/asm-arm/arm64/bitops.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/arm64/bitops.h
> b/xen/include/asm-arm/arm64/bitops.h
> index 6cc224ad13..d85a49bca4 100644
> --- a/xen/include/asm-arm/arm64/bitops.h
> +++ b/xen/include/asm-arm/arm64/bitops.h
> @@ -24,12 +24,13 @@ static /*__*/always_inline unsigned long __ffs(unsigned
> long word)
>
> static inline int flsl(unsigned long x)
> {
> - int ret;
> + uint64_t ret;
>
> if (__builtin_constant_p(x))
> return generic_flsl(x);
>
> asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
> +
> return BITS_PER_LONG - ret;
> }
>
> --
> 2.11.0
>
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