[musl] [PATCH v2] math: add riscv64 round/roundf

[musl] [PATCH v2] math: add riscv64 round/roundf

[Meng Zhuo]

---
v1 -> v2:
 * drop ±inf check and use fabs as Rich suggested
---
 src/math/riscv64/round.c  | 21 +++++++++++++++++++++
 src/math/riscv64/roundf.c | 21 +++++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 src/math/riscv64/round.c
 create mode 100644 src/math/riscv64/roundf.c

diff --git a/src/math/riscv64/round.c b/src/math/riscv64/round.c
new file mode 100644
index 00000000..81991b5f
--- /dev/null
+++ b/src/math/riscv64/round.c
@@ -0,0 +1,21 @@
+#include <math.h>
+
+#if __riscv_flen >= 64
+
+double round(double x)
+{
+	if (isnan(x)) return x;
+	if (fabs(x) >= 0x1p54) return x;
+	double tmp;
+	long long n;
+	__asm__ ("fcvt.l.d %0, %1, rmm" : "=r"(n) : "f"(x));
+	__asm__ ("fcvt.d.l %0, %1" : "=f"(tmp) : "r"(n));
+	__asm__ ("fsgnj.d %0, %1, %2" : "=f"(x) : "f"(tmp), "f"(x));
+	return x;
+}
+
+#else
+
+#include "../round.c"
+
+#endif
diff --git a/src/math/riscv64/roundf.c b/src/math/riscv64/roundf.c
new file mode 100644
index 00000000..cd2aebe5
--- /dev/null
+++ b/src/math/riscv64/roundf.c
@@ -0,0 +1,21 @@
+#include <math.h>
+
+#if __riscv_flen >= 32
+
+float roundf(float x)
+{
+	if (isnan(x)) return x;
+	if (fabsf(x) >= 0x1p25) return x;
+	float tmp;
+	long n;
+	__asm__ ("fcvt.w.s %0, %1, rmm" : "=r"(n) : "f"(x));
+	__asm__ ("fcvt.s.w %0, %1" : "=f"(tmp) : "r"(n));
+	__asm__ ("fsgnj.s %0, %1, %2" : "=f"(x) : "f"(tmp), "f"(x));
+	return x;
+}
+
+#else
+
+#include "../roundf.c"
+
+#endif
-- 
2.39.2

Re: [musl] [PATCH v2] math: add riscv64 round/roundf

[Rich Felker]

On Wed, Jun 12, 2024 at 11:14:13PM +0800, Meng Zhuo wrote:
> ---
> v1 -> v2:
>  * drop ±inf check and use fabs as Rich suggested

That is not the significant change. The significant change is fixing
completely wrong behavior on large finite inputs.

> ---
>  src/math/riscv64/round.c  | 21 +++++++++++++++++++++
>  src/math/riscv64/roundf.c | 21 +++++++++++++++++++++
>  2 files changed, 42 insertions(+)
>  create mode 100644 src/math/riscv64/round.c
>  create mode 100644 src/math/riscv64/roundf.c
> 
> diff --git a/src/math/riscv64/round.c b/src/math/riscv64/round.c
> new file mode 100644
> index 00000000..81991b5f
> --- /dev/null
> +++ b/src/math/riscv64/round.c
> @@ -0,0 +1,21 @@
> +#include <math.h>
> +
> +#if __riscv_flen >= 64
> +
> +double round(double x)
> +{
> +	if (isnan(x)) return x;
> +	if (fabs(x) >= 0x1p54) return x;

Did you keep the isnan test separate to avoid raising an exception, or
for other reasons?

Rich

Re: [musl] [PATCH v2] math: add riscv64 round/roundf

[Meng Zhuo]

Sorry, I'm not familiar to mail list contribution(first time) and send
another wrong patch(v3) for this.

I'll fix it.

Rich Felker <dalias@libc.org> 于2024年6月12日周三 23:18写道：
>
> On Wed, Jun 12, 2024 at 11:14:13PM +0800, Meng Zhuo wrote:
> > ---
> > v1 -> v2:
> >  * drop ±inf check and use fabs as Rich suggested
>
> That is not the significant change. The significant change is fixing
> completely wrong behavior on large finite inputs.
>
> > ---
> >  src/math/riscv64/round.c  | 21 +++++++++++++++++++++
> >  src/math/riscv64/roundf.c | 21 +++++++++++++++++++++
> >  2 files changed, 42 insertions(+)
> >  create mode 100644 src/math/riscv64/round.c
> >  create mode 100644 src/math/riscv64/roundf.c
> >
> > diff --git a/src/math/riscv64/round.c b/src/math/riscv64/round.c
> > new file mode 100644
> > index 00000000..81991b5f
> > --- /dev/null
> > +++ b/src/math/riscv64/round.c
> > @@ -0,0 +1,21 @@
> > +#include <math.h>
> > +
> > +#if __riscv_flen >= 64
> > +
> > +double round(double x)
> > +{
> > +     if (isnan(x)) return x;
> > +     if (fabs(x) >= 0x1p54) return x;
>
> Did you keep the isnan test separate to avoid raising an exception, or
> for other reasons?
>
> Rich
>