riscv: fmax/fmin sNaN fix

[Palmer Dabbelt]

On Mon, 19 Feb 2018 18:57:49 PST (-0800), dj@redhat.com wrote:
>
> RISC-V's FPU follows the IEEE spec, not the POSIX spec.  This patch
> adds handling for sNaN cases where the two specs differ.
>
> 	* sysdeps/riscv/rvd/s_fmax.c (__fmax): Handle sNaNs correctly.
> 	* sysdeps/riscv/rvd/s_fmin.c (__fmin): Likewise.
> 	* sysdeps/riscv/rvf/s_fmaxf.c (__fmaxf): Likewise.
> 	* sysdeps/riscv/rvf/s_fminf.c (__fminf): Likewise.
>
> diff --git a/sysdeps/riscv/rvd/s_fmax.c b/sysdeps/riscv/rvd/s_fmax.c
> index ef8f1344ce..22e91bfc4b 100644
> --- a/sysdeps/riscv/rvd/s_fmax.c
> +++ b/sysdeps/riscv/rvd/s_fmax.c
> @@ -17,12 +17,19 @@
>     <http://www.gnu.org/licenses/>.  */
>
>  #include <math.h>
> +#include <math_private.h>
>  #include <libm-alias-double.h>
>
>  double
>  __fmax (double x, double y)
>  {
> -  asm ("fmax.d %0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
> -  return x;
> +  double res;
> +
> +  if (__glibc_unlikely ((_FCLASS (x) | _FCLASS (y)) & _FCLASS_SNAN))
> +    return x + y;
> +  else
> +    asm ("fmax.d %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
> +
> +  return res;
>  }
>  libm_alias_double (__fmax, fmax)
> diff --git a/sysdeps/riscv/rvd/s_fmin.c b/sysdeps/riscv/rvd/s_fmin.c
> index c6ff24cefb..7b35230cac 100644
> --- a/sysdeps/riscv/rvd/s_fmin.c
> +++ b/sysdeps/riscv/rvd/s_fmin.c
> @@ -17,12 +17,19 @@
>     <http://www.gnu.org/licenses/>.  */
>
>  #include <math.h>
> +#include <math_private.h>
>  #include <libm-alias-double.h>
>
>  double
>  __fmin (double x, double y)
>  {
> -  asm ("fmin.d %0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
> -  return x;
> +  double res;
> +
> +  if (__glibc_unlikely ((_FCLASS (x) | _FCLASS (y)) & _FCLASS_SNAN))
> +    return x + y;
> +  else
> +    asm ("fmin.d %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
> +
> +  return res;
>  }
>  libm_alias_double (__fmin, fmin)
> diff --git a/sysdeps/riscv/rvf/s_fmaxf.c b/sysdeps/riscv/rvf/s_fmaxf.c
> index 3293f2f41c..63f7e3d664 100644
> --- a/sysdeps/riscv/rvf/s_fmaxf.c
> +++ b/sysdeps/riscv/rvf/s_fmaxf.c
> @@ -17,12 +17,19 @@
>     <http://www.gnu.org/licenses/>.  */
>
>  #include <math.h>
> +#include <math_private.h>
>  #include <libm-alias-float.h>
>
>  float
>  __fmaxf (float x, float y)
>  {
> -  asm ("fmax.s %0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
> -  return x;
> +  float res;
> +
> +  if (__glibc_unlikely ((_FCLASS (x) | _FCLASS (y)) & _FCLASS_SNAN))
> +    return x + y;
> +  else
> +    asm ("fmax.s %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
> +
> +  return res;
>  }
>  libm_alias_float (__fmax, fmax)
> diff --git a/sysdeps/riscv/rvf/s_fminf.c b/sysdeps/riscv/rvf/s_fminf.c
> index e4411f04b2..82cca4e37d 100644
> --- a/sysdeps/riscv/rvf/s_fminf.c
> +++ b/sysdeps/riscv/rvf/s_fminf.c
> @@ -17,12 +17,19 @@
>     <http://www.gnu.org/licenses/>.  */
>
>  #include <math.h>
> +#include <math_private.h>
>  #include <libm-alias-float.h>
>
>  float
>  __fminf (float x, float y)
>  {
> -  asm ("fmin.s %0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
> -  return x;
> +  float res;
> +
> +  if (__glibc_unlikely ((_FCLASS (x) | _FCLASS (y)) & _FCLASS_SNAN))
> +    return x + y;
> +  else
> +    asm ("fmin.s %0, %1, %2" : "=f" (res) : "f" (x), "f" (y));
> +
> +  return res;
>  }
>  libm_alias_float (__fmin, fmin)

Also looks good, modulo the commit message and ChangeLog.  Thanks!