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Fix ldbl-128ibm sqrtl (sNaN) (bug 20153) [committed]

Message ID alpine.DEB.2.20.1605262259040.6600@digraph.polyomino.org.uk
State New
Headers show

Commit Message

Joseph Myers May 26, 2016, 10:59 p.m. UTC 
The ldbl-128ibm implementation of sqrtl wrongly returns an sNaN for
signaling NaN arguments.  This patch fixes it to quiet its argument,
using the same x * x + x return for infinities and NaNs as the dbl-64
implementation uses to ensure that +Inf maps to +Inf while -Inf and
NaN map to NaN.

Tested for powerpc.  Committed.

2016-05-26  Joseph Myers  <joseph@codesourcery.com>

	[BZ #20153]
	* sysdeps/ieee754/ldbl-128ibm/e_sqrtl.c (__ieee754_sqrtl): Return
	x * x + x for infinities and NaNs.
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Patch

diff --git a/sysdeps/ieee754/ldbl-128ibm/e_sqrtl.c b/sysdeps/ieee754/ldbl-128ibm/e_sqrtl.c
index 96845fe..51365d6 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_sqrtl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_sqrtl.c
@@ -91,11 +91,9 @@  long double __ieee754_sqrtl(long double x)
     return c.x * i;
   }
   else {
-    if (k>=INT64_C(0x7ff0000000000000)) {
-      if (a.i[0] == INT64_C(0xfff0000000000000))
-	return (big1-big1)/(big-big); /* sqrt (-Inf) = NaN.  */
-      return x; /* sqrt (NaN) = NaN, sqrt (+Inf) = +Inf.  */
-    }
+    if (k>=INT64_C(0x7ff0000000000000))
+      /* sqrt (-Inf) = NaN, sqrt (NaN) = NaN, sqrt (+Inf) = +Inf.  */
+      return x * x + x;
     if (x == 0) return x;
     if (x < 0) return (big1-big1)/(big-big);
     return tm256*__ieee754_sqrtl(x*t512);