Re: [Qemu-devel] [PATCH] RISC-V: Fix isa string logic bug, use popcount to count bits

[Eric Blake]

[resend, this time with proper cc's]

On 03/09/2018 02:20 PM, Michael Clark wrote:
> Cc: Palmer Dabbelt <address@hidden>
> Cc: Peter Maydell <address@hidden>
> Signed-off-by: Michael Clark <address@hidden>
> ---
>   target/riscv/cpu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 4851890..f0d6d1d 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -391,7 +391,7 @@ static const TypeInfo riscv_cpu_type_info = {
>   char *riscv_isa_string(RISCVCPU *cpu)
>   {
>       int i;
> -    size_t maxlen = 5 + ctz32(cpu->env.misa);
> +    size_t maxlen = 5 + __builtin_popcountll(cpu->env.misa);
>       char *isa_string = g_new0(char, maxlen);
>       snprintf(isa_string, maxlen, "rv%d", TARGET_LONG_BITS);
>       for (i = 0; i < sizeof(riscv_exts); i++) {

I'd rather you used ctpop64() from host-utils.h, so we have a 
centralized place to change things just once in case we have to tweak 
the use of __builtin_popcount when targetting a different compiler.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org