[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-ppc] [PATCH] target/ppc: rewrite f[n]m[add, sub] using float64

From: Nikunj A Dadhania
Subject: Re: [Qemu-ppc] [PATCH] target/ppc: rewrite f[n]m[add, sub] using float64_muladd
Date: Wed, 01 Mar 2017 13:54:02 +0530
User-agent: Notmuch/0.21 (https://notmuchmail.org) Emacs/ (x86_64-redhat-linux-gnu)

Nikunj A Dadhania <address@hidden> writes:

> Bharata B Rao <address@hidden> writes:
>> On Wed, Mar 01, 2017 at 01:14:11PM +0530, Nikunj A Dadhania wrote:
>>> Use the softfloat api for fused multiply-add. As we are using the fused
>>> multiply-add, the intermediate result for setting VXISI is not
>>> available.
>> Isn't the behaviour of setting VXISI similar to vector muladd instructions ?
>> If so refer to VSX_MADD() to see when VXISI is set.
>                 if ((float64_is_infinity(xa.fld) ||
>                      float64_is_infinity(b->fld)) &&
>                      float64_is_infinity(c->fld))) {
>                    float_invalid_op_excp(env, POWERPC_EXCP_FP_VXISI, sfprf);
>                }
> AFAIU, VXISI is set when (infinity - infinity). The above doesn't take
> into consideration about substraction.

To be precise:

"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."


reply via email to

[Prev in Thread] Current Thread [Next in Thread]