Re: [PATCH v11 19/26] linux-user: Add LoongArch signal support

[Richard Henderson]

On 11/24/21 11:22 AM, gaosong wrote:
> I see that  kernel  define  the fcc used type uint64_t,   and  used movgr2cf/movcf2gr  
> save and restore the fcc0-fcc7.
> but  qemu define  fcc0-fcc7 as  bool cf[8] at target/loongarch/cpu.h,   how qemu can  
> save/restore fcc,  Do you have any idea?
> Does we can define the fcc   as   bool cf[8]  at  struct target_sigcontext?

No, you need to leave the declaration the same.

To create the uint64_t, you do what the kernel does in sc_save_fcc: insert each bit into 
the first bit of each byte.

static uint64_t read_all_fcc(CPULoongArchState *env)
{
    uint64_t ret = 0;

    for (int i = 0; i < 8; ++i) {
        ret |= (uint64_t)env->cf[i] << (i * 8);
    }
    return ret;
}

And similarly from sc_restore_fcc:

static void write_all_fcc(CPULoongArchState *env, uint64_t val)
{
    for (int i = 0; i < 8; ++i) {
        env->cf[i] = (val >> (i * 8)) & 1;
    }
}

Remembering that movcf2gr copies the least significant bit.


r~