On Mon, Jan 17, 2022 at 12:11:59AM +0100, FX via Gcc-patches wrote:
> This patch is the third in my “signaling NaN” series. For targets with IEEE
> support but without the issignaling macro in libc (i.e., everywhere except
> glibc), this allows us to provide a fallback implementation. In order to keep
> the code in ieee_helper.c relatively readable, I’ve put that new
> implementation in a separate file, issignaling_fallback.h.
>
> The logic is borrowed from different routines in glibc, but gathered into a
> single file and much simpler than the glibc implementation, because we do not
> need to cover all the cases they have (comments with details are available in
> issignaling_fallback.h).
>
> I can’t test this on all the targets I’d like to, obviously. But it was
> tested on x86_64-pc-linux-gnu (where it doesn’t do anything), on
> x86_64-pc-linux-gnu by mimicking the lack of a issignaling macro, and on
> x86_64-apple-darwin (which does not have issignaling).
This doesn't seem to handle the powerpc* IBM double double long double.
__LDBL_IS_IEC_60559__ isn't defined for this type, because it is far from
an IEEE754 type, but it has signaling NaNs - as can be seen in glibc
libc/sysdeps/ieee754/ldbl-128ibm/s_issignalingl.c
the type is a pair of doubles and whether it is a sNaN or qNaN is determined
by whether the first double is a sNaN or qNaN.
Ok for trunk?
2022-01-25 Jakub Jelinek <ja...@redhat.com>
* ieee/issignaling_fallback.h (__issignalingl): Define for
IBM extended long double are returning __issignaling on the
first double.
--- libgfortran/ieee/issignaling_fallback.h.jj 2022-01-25 12:14:45.404232320
+0100
+++ libgfortran/ieee/issignaling_fallback.h 2022-01-25 12:14:52.504131720
+0100
@@ -137,6 +137,19 @@ __issignalingl (long double x)
return ret || (((exi & 0x7fff) == 0x7fff) && (hxi > 0xc0000000));
}
+#elif (__LDBL_DIG__ == 31)
+
+/* Long double is 128-bit IBM extended type. */
+
+static inline int
+__issignalingl (long double x)
+{
+ union { long double value; double parts[2]; } u;
+
+ u.value = x;
+ return __issignaling (u.parts[0]);
+}
+
#elif (__LDBL_DIG__ == 33) && __LDBL_IS_IEC_60559__
/* Long double is 128-bit type. */
Jakub
