Re: [Qemu-devel] [PATCH v5 06/23] Softfloat support for IEEE 754-201x minimumNumber/maximumNumber

[Michael Clark]

On Fri, Feb 9, 2018 at 3:35 AM, Richard Henderson <
richard.hender...@linaro.org> wrote:

> On 02/07/2018 05:28 PM, Michael Clark wrote:
> > QEMU currently implements IEEE 754-2008 minNum/maxNum. This patch adds
> > support for IEEE 754-201x minimumNumber/maximumNumber which is required
> > by the RISC-V port.
> >
> > minNum(x, y) is defined as
> > - min(x, y) if neither is NaN
> > - if one of x and y is a number and one is qNaN, return the number
> > - if both are qNaN, or either is sNaN, return NaN
> >
> > minimumNumber(x, y) is defined as
> > - min(x, y) if neither is NaN
> > - if one of x and y is a number and one is qNaN or sNaN, return the
> number
> > - if both are NaN, return the number
> >
> > Both functions signal the invalid exception on sNaN inputs.
> >
> > Signed-off-by: Michael Clark 
> > ---
>
> Thanks for the description of the function.  We've got a reorg of softfloat
> pending at the moment; I'd want to defer this patch until that set has
> landed.
>

Noted.

We should also add a mention of minimumNumber/maximumNumber to the
preceeding comment, which isn't in the current version of the patch. e.g.

 * minimumnumber() and maximumnumber() functions correspond to
minimumNumber()
 * and maximumNumber() from the IEEE-754 201x specification.

Re: [Qemu-devel] [PATCH v5 06/23] Softfloat support for IEEE 754-201x minimumNumber/maximumNumber

[Richard Henderson]

On 02/07/2018 05:28 PM, Michael Clark wrote:
> QEMU currently implements IEEE 754-2008 minNum/maxNum. This patch adds
> support for IEEE 754-201x minimumNumber/maximumNumber which is required
> by the RISC-V port.
> 
> minNum(x, y) is defined as
> - min(x, y) if neither is NaN
> - if one of x and y is a number and one is qNaN, return the number
> - if both are qNaN, or either is sNaN, return NaN
> 
> minimumNumber(x, y) is defined as
> - min(x, y) if neither is NaN
> - if one of x and y is a number and one is qNaN or sNaN, return the number
> - if both are NaN, return the number
> 
> Both functions signal the invalid exception on sNaN inputs.
> 
> Signed-off-by: Michael Clark 
> ---

Thanks for the description of the function.  We've got a reorg of softfloat
pending at the moment; I'd want to defer this patch until that set has landed.


r~

[Qemu-devel] [PATCH v5 06/23] Softfloat support for IEEE 754-201x minimumNumber/maximumNumber

[Michael Clark]

QEMU currently implements IEEE 754-2008 minNum/maxNum. This patch adds
support for IEEE 754-201x minimumNumber/maximumNumber which is required
by the RISC-V port.

minNum(x, y) is defined as
- min(x, y) if neither is NaN
- if one of x and y is a number and one is qNaN, return the number
- if both are qNaN, or either is sNaN, return NaN

minimumNumber(x, y) is defined as
- min(x, y) if neither is NaN
- if one of x and y is a number and one is qNaN or sNaN, return the number
- if both are NaN, return the number

Both functions signal the invalid exception on sNaN inputs.

Signed-off-by: Michael Clark 
---
 fpu/softfloat.c | 41 +++--
 include/fpu/softfloat.h |  4 
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 433c5da..5793cc9 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -7675,6 +7675,9 @@ int float128_compare_quiet(float128 a, float128 b, 
float_status *status)
  * minnummag() and maxnummag() functions correspond to minNumMag()
  * and minNumMag() from the IEEE-754 2008.
  */
+
+enum { ieee2008 = 1, ieee201x = 2 };
+
 #define MINMAX(s)   \
 static inline float ## s float ## s ## _minmax(float ## s a, float ## s b, 
\
int ismin, int isieee,   \
@@ -7687,12 +7690,26 @@ static inline float ## s float ## s ## _minmax(float ## 
s a, float ## s b, \
 b = float ## s ## _squash_input_denormal(b, status);\
 if (float ## s ## _is_any_nan(a) || \
 float ## s ## _is_any_nan(b)) { \
-if (isieee) {   \
+if (isieee == ieee2008) {   \
 if (float ## s ## _is_quiet_nan(a, status) &&   \
 !float ## s ##_is_any_nan(b)) { \
 return b;   \
 } else if (float ## s ## _is_quiet_nan(b, status) &&\
-   !float ## s ## _is_any_nan(a)) {\
+   !float ## s ## _is_any_nan(a)) { \
+return a;   \
+}   \
+} else if (isieee == ieee201x) {\
+if (float ## s ## _is_any_nan(a) && \
+!float ## s ##_is_any_nan(b)) { \
+if (!float ## s ## _is_quiet_nan(a, status)) {  \
+float_raise(float_flag_invalid, status);\
+}   \
+return b;   \
+} else if (float ## s ## _is_any_nan(b) &&  \
+   !float ## s ## _is_any_nan(a)) { \
+if (!float ## s ## _is_quiet_nan(b, status)) {  \
+float_raise(float_flag_invalid, status);\
+}   \
 return a;   \
 }   \
 }   \
@@ -7743,25 +7760,37 @@ float ## s float ## s ## _max(float ## s a, float ## s 
b,   \
 float ## s float ## s ## _minnum(float ## s a, float ## s b,\
  float_status *status)  \
 {   \
-return float ## s ## _minmax(a, b, 1, 1, 0, status);\
+return float ## s ## _minmax(a, b, 1, ieee2008, 0, status); \
 }   \
 \
 float ## s float ## s ## _maxnum(float ## s a, float ## s b,\
  float_status *status)  \
 {   \
-return float ## s ## _minmax(a, b, 0, 1, 0, status);\
+return float ## s ## _minmax(a, b, 0, ieee2008, 0, status); \
+}   \
+\
+float ## s float ## s ## _minimumnumber(float ## s a, float ## s b, \
+ float_status *status)  \
+{   \
+return float ## s ## _minmax(a, b, 1