Fix hypot sNaN handling (bug 20940).

TS 18661-1 generally defines libm functions taking sNaN arguments to
return qNaN and raise "invalid", even for the cases where a
corresponding qNaN argument would not result in a qNaN return.  This
includes hypot with one argument being an infinity and the other being
an sNaN.  This patch duly fixes hypot implementatations in glibc
(generic and powerpc) to ensure qNaN, computed by arithmetic on the
arguments, is returned in that case.

Various implementations do their checks for infinities and NaNs inline
by manipulating the representations of the arguments.  For simplicity,
this patch just uses issignaling to check for sNaN arguments.  This
could be inlined like the existing code (with due care about reversed
quiet NaN conventions, for implementations where that is relevant),
but given that all these checks are in cases where it's already known
at least one argument is not finite, which should be the uncommon
case, that doesn't seem worthwhile unless performance issues are
observed in practice.

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #20940]
	* sysdeps/ieee754/dbl-64/e_hypot.c (__ieee754_hypot): Do not
	return Inf for arguments Inf and sNaN.
	* sysdeps/ieee754/flt-32/e_hypotf.c (__ieee754_hypotf): Likewise.
	* sysdeps/ieee754/ldbl-128/e_hypotl.c (__ieee754_hypotl):
	Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl):
	Likewise.
	* sysdeps/ieee754/ldbl-96/e_hypotl.c (__ieee754_hypotl): Likewise.
	* sysdeps/powerpc/fpu/e_hypot.c (TEST_INF_NAN): Do not return Inf
	for arguments Inf and sNaN.  When returning a NaN, compute it by
	arithmetic on the arguments.
	* sysdeps/powerpc/fpu/e_hypotf.c (TEST_INF_NAN): Likewise.
	* math/libm-test.inc (pow_test_data): Add tests of sNaN arguments.

5 files changed, 10 insertions, 2 deletions

diff --git a/sysdeps/ieee754/dbl-64/e_hypot.c b/sysdeps/ieee754/dbl-64/e_hypot.c
index f142c450a2..76eb408348 100644
--- a/sysdeps/ieee754/dbl-64/e_hypot.c
+++ b/sysdeps/ieee754/dbl-64/e_hypot.c
@@ -76,6 +76,8 @@ __ieee754_hypot (double x, double y)
 	{
 	  u_int32_t low;
 	  w = a + b;                    /* for sNaN */
+	  if (issignaling (a) || issignaling (b))
+	    return w;
 	  GET_LOW_WORD (low, a);
 	  if (((ha & 0xfffff) | low) == 0)
 	    w = a;
diff --git a/sysdeps/ieee754/flt-32/e_hypotf.c b/sysdeps/ieee754/flt-32/e_hypotf.c
index 717b82e42f..fda2651a84 100644
--- a/sysdeps/ieee754/flt-32/e_hypotf.c
+++ b/sysdeps/ieee754/flt-32/e_hypotf.c
@@ -26,9 +26,9 @@ __ieee754_hypotf(float x, float y)
 	ha &= 0x7fffffff;
 	GET_FLOAT_WORD(hb,y);
 	hb &= 0x7fffffff;
-	if (ha == 0x7f800000)
+	if (ha == 0x7f800000 && !issignaling (y))
 	  return fabsf(x);
-	else if (hb == 0x7f800000)
+	else if (hb == 0x7f800000 && !issignaling (x))
 	  return fabsf(y);
 	else if (ha > 0x7f800000 || hb > 0x7f800000)
 	  return fabsf(x) * fabsf(y);
diff --git a/sysdeps/ieee754/ldbl-128/e_hypotl.c b/sysdeps/ieee754/ldbl-128/e_hypotl.c
index a93f5a4c8f..6c4e178fbe 100644
--- a/sysdeps/ieee754/ldbl-128/e_hypotl.c
+++ b/sysdeps/ieee754/ldbl-128/e_hypotl.c
@@ -67,6 +67,8 @@ __ieee754_hypotl(_Float128 x, _Float128 y)
 	   if(ha >= 0x7fff000000000000LL) {	/* Inf or NaN */
 	       u_int64_t low;
 	       w = a+b;			/* for sNaN */
+	       if (issignaling (a) || issignaling (b))
+		 return w;
 	       GET_LDOUBLE_LSW64(low,a);
 	       if(((ha&0xffffffffffffLL)|low)==0) w = a;
 	       GET_LDOUBLE_LSW64(low,b);
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_hypotl.c b/sysdeps/ieee754/ldbl-128ibm/e_hypotl.c
index c68dac03b0..de5a66ab05 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_hypotl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_hypotl.c
@@ -67,6 +67,8 @@ __ieee754_hypotl(long double x, long double y)
 	if(ha > 0x5f30000000000000LL) {	/* a>2**500 */
 	   if(ha >= 0x7ff0000000000000LL) {	/* Inf or NaN */
 	       w = a+b;			/* for sNaN */
+	       if (issignaling (a) || issignaling (b))
+		 return w;
 	       if(ha == 0x7ff0000000000000LL)
 		 w = a;
 	       if(hb == 0x7ff0000000000000LL)
diff --git a/sysdeps/ieee754/ldbl-96/e_hypotl.c b/sysdeps/ieee754/ldbl-96/e_hypotl.c
index ee3a07055b..6b55b6d8ee 100644
--- a/sysdeps/ieee754/ldbl-96/e_hypotl.c
+++ b/sysdeps/ieee754/ldbl-96/e_hypotl.c
@@ -68,6 +68,8 @@ long double __ieee754_hypotl(long double x, long double y)
 	       u_int32_t exp __attribute__ ((unused));
 	       u_int32_t high,low;
 	       w = a+b;			/* for sNaN */
+	       if (issignaling (a) || issignaling (b))
+		 return w;
 	       GET_LDOUBLE_WORDS(exp,high,low,a);
 	       if(((high&0x7fffffff)|low)==0) w = a;
 	       GET_LDOUBLE_WORDS(exp,high,low,b);