[3/7] target/m68k: add fsglmul and fsgldiv

fsglmul and fsgldiv truncate data to single precision before computing
results.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 target/m68k/fpu_helper.c | 22 ++++++++++++++++++++++
 target/m68k/helper.h     |  2 ++
 target/m68k/translate.c  |  6 ++++++
 3 files changed, 30 insertions(+)

Hi Laurent,

On 06/25/2017 04:21 PM, Laurent Vivier wrote:
> fsglmul and fsgldiv truncate data to single precision before computing
> results.
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>   target/m68k/fpu_helper.c | 22 ++++++++++++++++++++++
>   target/m68k/helper.h     |  2 ++
>   target/m68k/translate.c  |  6 ++++++
>   3 files changed, 30 insertions(+)
> 
> diff --git a/target/m68k/fpu_helper.c b/target/m68k/fpu_helper.c
> index 912c0b7..0d83925 100644
> --- a/target/m68k/fpu_helper.c
> +++ b/target/m68k/fpu_helper.c
> @@ -183,11 +183,33 @@ void HELPER(fmul)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
>       res->d = floatx80_mul(val0->d, val1->d, &env->fp_status);
>   }
>   
> +void HELPER(fsglmul)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
> +{
> +    float32 a, b, c;
> +
> +    a = floatx80_to_float32(val0->d, &env->fp_status);
> +    b = floatx80_to_float32(val1->d, &env->fp_status);
> +    c = float32_mul(a, b, &env->fp_status);

Why not use floatx80_mul() directly?

> +
> +    res->d = float32_to_floatx80(c, &env->fp_status);
> +}
> +
>   void HELPER(fdiv)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
>   {
>       res->d = floatx80_div(val1->d, val0->d, &env->fp_status);
>   }
>   
> +void HELPER(fsgldiv)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg *val1)
> +{
> +    float32 a, b, c;
> +
> +    a = floatx80_to_float32(val1->d, &env->fp_status);
> +    b = floatx80_to_float32(val0->d, &env->fp_status);
> +    c = float32_div(a, b, &env->fp_status);

floatx80_div()?

> +
> +    res->d = float32_to_floatx80(c, &env->fp_status);
> +}
> +
>   static int float_comp_to_cc(int float_compare)
>   {
>       switch (float_compare) {
> diff --git a/target/m68k/helper.h b/target/m68k/helper.h
> index d6e80e4..5a006de 100644
> --- a/target/m68k/helper.h
> +++ b/target/m68k/helper.h
> @@ -31,7 +31,9 @@ DEF_HELPER_3(fchs, void, env, fp, fp)
>   DEF_HELPER_4(fadd, void, env, fp, fp, fp)
>   DEF_HELPER_4(fsub, void, env, fp, fp, fp)
>   DEF_HELPER_4(fmul, void, env, fp, fp, fp)
> +DEF_HELPER_4(fsglmul, void, env, fp, fp, fp)
>   DEF_HELPER_4(fdiv, void, env, fp, fp, fp)
> +DEF_HELPER_4(fsgldiv, void, env, fp, fp, fp)
>   DEF_HELPER_FLAGS_3(fcmp, TCG_CALL_NO_RWG, void, env, fp, fp)
>   DEF_HELPER_FLAGS_2(set_fpcr, TCG_CALL_NO_RWG, void, env, i32)
>   DEF_HELPER_FLAGS_2(ftst, TCG_CALL_NO_RWG, void, env, fp)
> diff --git a/target/m68k/translate.c b/target/m68k/translate.c
> index a54da87..a50bf5f 100644
> --- a/target/m68k/translate.c
> +++ b/target/m68k/translate.c
> @@ -4622,6 +4622,12 @@ DISAS_INSN(fpu)
>       case 0x23: case 0x63: case 0x67: /* fmul */
>           gen_helper_fmul(cpu_env, cpu_dest, cpu_src, cpu_dest);
>           break;
> +    case 0x24: /* fsgldiv */
> +        gen_helper_fsgldiv(cpu_env, cpu_dest, cpu_src, cpu_dest);
> +        break;
> +    case 0x27: /* fsglmul */
> +        gen_helper_fsglmul(cpu_env, cpu_dest, cpu_src, cpu_dest);
> +        break;
>       case 0x28: case 0x68: case 0x6c: /* fsub */
>           gen_helper_fsub(cpu_env, cpu_dest, cpu_src, cpu_dest);
>           break;
>

Le 25/06/2017 à 21:44, Philippe Mathieu-Daudé a écrit :
> Hi Laurent,
> 
> On 06/25/2017 04:21 PM, Laurent Vivier wrote:
>> fsglmul and fsgldiv truncate data to single precision before computing
>> results.
>>
>> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
>> ---
>>   target/m68k/fpu_helper.c | 22 ++++++++++++++++++++++
>>   target/m68k/helper.h     |  2 ++
>>   target/m68k/translate.c  |  6 ++++++
>>   3 files changed, 30 insertions(+)
>>
>> diff --git a/target/m68k/fpu_helper.c b/target/m68k/fpu_helper.c
>> index 912c0b7..0d83925 100644
>> --- a/target/m68k/fpu_helper.c
>> +++ b/target/m68k/fpu_helper.c
>> @@ -183,11 +183,33 @@ void HELPER(fmul)(CPUM68KState *env, FPReg *res,
>> FPReg *val0, FPReg *val1)
>>       res->d = floatx80_mul(val0->d, val1->d, &env->fp_status);
>>   }
>>   +void HELPER(fsglmul)(CPUM68KState *env, FPReg *res, FPReg *val0,
>> FPReg *val1)
>> +{
>> +    float32 a, b, c;
>> +
>> +    a = floatx80_to_float32(val0->d, &env->fp_status);
>> +    b = floatx80_to_float32(val1->d, &env->fp_status);
>> +    c = float32_mul(a, b, &env->fp_status);
> 
> Why not use floatx80_mul() directly?
> 
>> +
>> +    res->d = float32_to_floatx80(c, &env->fp_status);
>> +}
>> +
>>   void HELPER(fdiv)(CPUM68KState *env, FPReg *res, FPReg *val0, FPReg
>> *val1)
>>   {
>>       res->d = floatx80_div(val1->d, val0->d, &env->fp_status);
>>   }
>>   +void HELPER(fsgldiv)(CPUM68KState *env, FPReg *res, FPReg *val0,
>> FPReg *val1)
>> +{
>> +    float32 a, b, c;
>> +
>> +    a = floatx80_to_float32(val1->d, &env->fp_status);
>> +    b = floatx80_to_float32(val0->d, &env->fp_status);
>> +    c = float32_div(a, b, &env->fp_status);
> 
> floatx80_div()?
> 

Just to follow the spec of the instruction:

"if either operand requires more than 24 bits of mantissa to be
accurately represented, the extraneous mantissa bits are truncated prior
to the multiplication;"

Do you think I should keep them in floatx80 and use the floatx80_round()
(I introduce latter in the series) to reduce the precision prior the
floatx80_mul()?

Thanks,
Laurent

On 06/26/2017 01:05 AM, Laurent Vivier wrote:
>> floatx80_div()?
>>
> 
> Just to follow the spec of the instruction:
> 
> "if either operand requires more than 24 bits of mantissa to be
> accurately represented, the extraneous mantissa bits are truncated prior
> to the multiplication;"
> 
> Do you think I should keep them in floatx80 and use the floatx80_round()
> (I introduce latter in the series) to reduce the precision prior the
> floatx80_mul()?

Actually, yes.  The spec explicitly says that the exponent will be in extended 
precision.


r~