[PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[frank.chang]

From: Frank Chang <frank.chang@sifive.com>

In IEEE 754-2008 spec:
  Invalid operation exception is signaled when doing:
  fusedMultiplyAdd(0, Inf, c) or fusedMultiplyAdd(Inf, 0, c)
  unless c is a quiet NaN; if c is a quiet NaN then it is
  implementation defined whether the invalid operation exception
  is signaled.

In RISC-V Unprivileged ISA spec:
  The fused multiply-add instructions must set the invalid
  operation exception flag when the multiplicands are Inf and
  zero, even when the addend is a quiet NaN.

This commit set invalid operation execption flag for RISC-V when
multiplicands of muladd instructions are Inf and zero.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
---
 fpu/softfloat-specialize.c.inc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index c2f87addb25..12f29fbfc5e 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -624,6 +624,12 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass b_cls, FloatClass c_cls,
     } else {
         return 1;
     }
+#elif defined(TARGET_RISCV)
+    /* For RISC-V, InvalidOp is set when multiplicands are Inf and zero */
+    if (infzero) {
+        float_raise(float_flag_invalid, status);
+    }
+    return 3; /* deafult NaN */
 #elif defined(TARGET_XTENSA)
     /*
      * For Xtensa, the (inf,zero,nan) case sets InvalidOp and returns
-- 
2.17.1

Re: [PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[Richard Henderson]

On 4/19/21 6:31 PM, frank.chang@sifive.com wrote:
> From: Frank Chang<frank.chang@sifive.com>
> 
> In IEEE 754-2008 spec:
>    Invalid operation exception is signaled when doing:
>    fusedMultiplyAdd(0, Inf, c) or fusedMultiplyAdd(Inf, 0, c)
>    unless c is a quiet NaN; if c is a quiet NaN then it is
>    implementation defined whether the invalid operation exception
>    is signaled.
> 
> In RISC-V Unprivileged ISA spec:
>    The fused multiply-add instructions must set the invalid
>    operation exception flag when the multiplicands are Inf and
>    zero, even when the addend is a quiet NaN.
> 
> This commit set invalid operation execption flag for RISC-V when
> multiplicands of muladd instructions are Inf and zero.
> 
> Signed-off-by: Frank Chang<frank.chang@sifive.com>
> ---
>   fpu/softfloat-specialize.c.inc | 6 ++++++
>   1 file changed, 6 insertions(+)
> 

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Alistair, will you take this via your riscv queue?


r~

Re: [PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[Alistair Francis]

On Wed, Apr 21, 2021 at 12:17 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 4/19/21 6:31 PM, frank.chang@sifive.com wrote:
> > From: Frank Chang<frank.chang@sifive.com>
> >
> > In IEEE 754-2008 spec:
> >    Invalid operation exception is signaled when doing:
> >    fusedMultiplyAdd(0, Inf, c) or fusedMultiplyAdd(Inf, 0, c)
> >    unless c is a quiet NaN; if c is a quiet NaN then it is
> >    implementation defined whether the invalid operation exception
> >    is signaled.
> >
> > In RISC-V Unprivileged ISA spec:
> >    The fused multiply-add instructions must set the invalid
> >    operation exception flag when the multiplicands are Inf and
> >    zero, even when the addend is a quiet NaN.
> >
> > This commit set invalid operation execption flag for RISC-V when
> > multiplicands of muladd instructions are Inf and zero.
> >
> > Signed-off-by: Frank Chang<frank.chang@sifive.com>
> > ---
> >   fpu/softfloat-specialize.c.inc | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>
> Alistair, will you take this via your riscv queue?

Yep, getting it now

Alistair

>
>
> r~
>

Re: [PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[Richard Henderson]

On 4/19/21 6:31 PM, frank.chang@sifive.com wrote:
> +    return 3; /* deafult NaN */

Late notice of spelling error: default.

r~

Re: [PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

[Alistair Francis]

On Thu, Apr 22, 2021 at 11:06 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 4/19/21 6:31 PM, frank.chang@sifive.com wrote:
> > +    return 3; /* deafult NaN */
>
> Late notice of spelling error: default.

Fixed when I applied it.

Thanks!

Applied to riscv-to-apply.next

Alistair

>
> r~
>