On Wed, 27 Mar 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 asm statement expects a 32-bit (resp. 64-bit) value on Arm32
> (resp. Arm64) whereas the value is a boolean (Clang consider to be
> 32-bit).
>
> It would be possible to impose 32-bit register for both architecture
> but this require the code to use __OP32. However, it does no really
> improve the assembly generated. Instead, replace switch the variable to
> use register_t.
>
> Signed-off-by: Julien Grall <julien.gr...@arm.com>
> ---
> xen/include/asm-arm/cpufeature.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/cpufeature.h
> b/xen/include/asm-arm/cpufeature.h
> index c2c8f3417c..d06f09ecfa 100644
> --- a/xen/include/asm-arm/cpufeature.h
> +++ b/xen/include/asm-arm/cpufeature.h
> @@ -67,7 +67,7 @@ static inline bool cpus_have_cap(unsigned int num)
>
> /* System capability check for constant cap */
> #define cpus_have_const_cap(num) ({ \
> - bool __ret; \
> + register_t __ret; \
> \
> asm volatile (ALTERNATIVE("mov %0, #0", \
> "mov %0, #1", \
As per the previous one, this is fine, but could you also change the
last statement below to unlikely(!!__ret);
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