Re: [PATCH v11 11/26] target/loongarch: Add floating point comparison instruction translation

[gaosong]

Hi Richard,

On 2021/11/20 下午5:02, Richard Henderson wrote:

> > +#define FCMP_LT  
> >         0x0001  /* fp0 < fp1 */
> >         
> >         +#define FCMP_EQ   0x0010  /* fp0 = fp1 */
> >         
> >         +#define FCMP_UN   0x0100  /* unordered */
> >         
> >         +#define FCMP_GT   0x1000  /* fp0 > fp1 */
> >         
> >       
>       
>       Any reason why these bits are not sequential?
>     
    I think this is consistent with the description in Table 9,  and the
    FCMP_GT is need 0x7.
    In  get_fcmp_flags(int cond)  the param 'cond' is table 9  COND
    >> 1,  
    
    table 9
    COND          True Condition
    0x2              LT
    0x4              EQ
    0x6              EQ  LT
    0x8              UN
    0x10            GT LT
    ...
    COND >> 1   Flags
    0x1              FCMP_LT                            FCMP_LT    0x1 
    0x2              FCMP_EQ                           FCMP_EQ    0x2
    0x3              FCMP_EQ  |  FCMP_LT         
    0x4              FCMP_UN                          FCMP_UN   0x4
    0x8              FCMP_GT |  FCMP_LT          FCMP_GT    0x7
    ...
    so our definitions :
    #define FCMP_LT    0x1  /* fp0 < fp1 */
    #define FCMP_EQ   0x2  /* fp0 = fp1 */
    #define FCMP_UN   0x4  /* unordered */
    #define FCMP_GT   0x7  /* fp0 > fp1 */
    
    get_fcmp_flags:
    /* bit0(signaling/quiet) bit1(lt) bit2(eq) bit3(un) bit4(neq) */
    static uint32_t get_fcmp_flags(int cond)
    {
        uint32_t flags = 0;
    
        if (cond & 0x1) {
            flags |= FCMP_LT;
        }
        if (cond & 0x2) {
            flags |= FCMP_EQ;
        }
        if (cond & 0x4) {
            flags |= FCMP_UN;
        }
        if (cond & 0x8) {
            flags |= FCMP_GT | FCMP_LT;
        }
        return flags;
    }

If not .

We should like:

#define FCMP_LT    0x1  /* fp0 < fp1 */
#define FCMP_EQ   0x2  /* fp0 = fp1 */
#define FCMP_UN   0x3  /* unordered */
#define FCMP_GT   0x4  /* fp0 > fp1 */

static uint32_t get_fcmp_flags(int cond)
{
    uint32_t flags = 0;

    if (cond & 0x1) {
        flags |= FCMP_LT;
    }
    if (cond & 0x2) {
        flags |= FCMP_EQ;
    }
    if (cond & 0x3) {
        flags |= FCMP_UN;
    }
    if (cond & 0x4) {
        flags |= FCMP_GT;
    }
    return flags;
}

Is this right?

    Thanks
    Song Gao