On 02-Mar-2017 8:07 AM, "Richard Henderson" <r...@twiddle.net> wrote:
>
> On 03/02/2017 02:24 AM, Nikunj A Dadhania wrote:
>
>> +static void float64_madd_set_vxisi(CPUPPCState *env, float64 a, float64
>> b,
>> + float64 c, unsigned int flags)
>> {
>> + float64 f = float64_mul(a, b, &env->fp_status);
>>
>
> What is the point of this multiply?
>
>
Only to compute vxisi as stated in the thread
"If the product of x and y is an Infinity and z is an Infinity of the
opposite sign, vxisi_flag is set to 1."
Let me know if I there is an alternative way to achieve this.
>> + /* a*b = ∞ and c = ∞, find ∞ - ∞ case and set VXISI */
>> + if (float64_is_infinity(f) && float64_is_infinity(c)) {
>> + if ((f ^ c) == 0) {
>> + /* Both negative/positive inifinity and substraction*/
>> + if (flags & MSUB_FLGS) {
>>
>
> I would really prefer you use the float_muladd_* names.
Sure.
> +uint64_t helper_##op(CPUPPCState *env, uint64_t arg1, \
>> + uint64_t arg2, uint64_t arg3) \
>> +{ \
>> + if (unlikely((float64_is_infinity(arg1) && float64_is_zero(arg2)) ||
>> \
>> + (float64_is_zero(arg1) && float64_is_infinity(arg2)))) {
>> \
>> + /* Multiplication of zero by infinity */ \
>> + arg1 = float_invalid_op_excp(env, POWERPC_EXCP_FP_VXIMZ, 1); \
>> + } else { \
>> + if (unlikely(float64_is_signaling_nan(arg1, &env->fp_status) || \
>> + float64_is_signaling_nan(arg2, &env->fp_status) || \
>> + float64_is_signaling_nan(arg3, &env->fp_status))) {
>> \
>> + /* sNaN operation */ \
>> + float_invalid_op_excp(env, POWERPC_EXCP_FP_VXSNAN, 1); \
>> + } \
>> + \
>> + float64_madd_set_vxisi(env, arg1, arg2, arg3, madd_flags); \
>> + arg1 = float64_muladd(arg1, arg2, arg3, madd_flags, \
>> + &env->fp_status); \
>> + float_check_status(env); \
>>
>
> I know this is the layout of the bulk of the ppc target, but it's
> inefficient. Let's do this one correctly, akin to target/tricore:
>
> result = float64_muladd(args...);
> flags = get_float_exception_flags(&env->fp_status);
> if (flags) {
> if (flags & float_flag_invalid) {
> // examine inputs to see why we return NaN
> }
> float_check_status(env);
> }
Sure.
Nikunj
